Sistema K JETRONIC

Trata-se de informações sobre o sistema k-jetrônic. Peço desculpas aos confrades, é muito grande para traduzir e postar aqui, mas segue o link para consultas, são 17 páginas....

http://www.users.bigpond.com/INTERJECT/KJETRON.HTM#THE%20WARM

C.I.S., or in Australia and USA, known as K-JETRONIC, is a constant injection system. This means that instead of injectors being pulsed by electric current, they are pressurised from the fuel distributor head. On idle there is small pressure with constant flow to the injectors. The spray is only to describe a dribble from the injectors. It is wrong if other mechanics tell you the spray pattern must be atomised. No, it is just continuously DRIBBLING fuel into the manifold regardless of ignition timing while the engine is idling. If the RPM of this engine is increased, then more air will be drawn into the combustion chamber, which lifts the air sensor plate higher up, or on other engine models, down. The sensor plate moves a metering pin in the fuel distributor upwards which allows more fuel to pass through the micro slit. The pressure and FLOW in the top cavity of the fuel distributor will rise automatically, where by, the thin stainless steel separation plate bends downwards. More fuel FLOW can enter into the injector lines and the injectors spray constantly the exact amount of fuel required to the engine. The injectors make a sound, similar to resonating pressure and flow discharge on a power steering pump. Depending on how high the sensor plate is being lifted, the discharge sound will change its pitch. At this point the atomisation of the fuel which has been discharged from the injectors is not very critical. I'm saying you can have a cone spray or 3,2 or even 1 way spray. What is critical on K-Jetronic is the VOLUME of fuel. Measured in test beakers, there must be as close as possible to an equal amount of fuel in all the other test beakers.
There are very few technicians in Australia who know enough about K-Jetronic fuel injection to effectively repair it. The majority of these technicians have this capability due to their extensive training with INTER-JECT equipment and products. The equipment needed to service these systems is, the LB-288/4, the cheaper LB-291, the LB-291/F, or the most advanced LB-291/2F. These instruments are designed for EFI and K-Jetronic systems, which work on the principal of FLOW and PRESSURE. Unless you have the necessary equipment or skills, my advice is leave it alone, if the car is running well. The K-Jetronic system is usually fitted to vehicles around the $80,000 mark and mistakes when repairing them are costly to either the client whose business you could lose, or your business if it is your mistake. Under no circumstances should you attempt to clean the injectors using an aerosol system. The reason for this is quite simple, using the aerosol system necessitates blocking off the fuel return line, and doing this will damage the fuel distributor, which YOU may have to pay for at considerable cost. The reasons that this will happen are:
a: The counter pressure on top of the metering pin will be so high that the air sensor plate will be locked.
b: Due to the locking of the sensor plate, the full pressure of the aerosol can will destroy the seals in the fuel distributor immediately. Believe me, you can count on that.
c: If you do not crimp off the return line and are still using an aerosol can for cleaning, it would take approximately 30 seconds and the whole contents of the aerosol can will end up in the fuel tank.
THE FUEL DISTRIBUTORS ON K-JETRONIC ARE two halves of a casting or block. The bottom half has four to eight cavities, and the upper casting has the same amount of cavities, depending on the size of engine. A very thin stainless steel separation plate separates the pressure chambers which are also flow chambers.
PLEASE NOTE, you cannot have flow if you do not have pressure or vice versa, and flow creates the pressure which then depends on how much pressure you have. The end result is how much flow is remaining which you measure with the system flow meter. So by sealing with "O" rings the entry channels to all flow chambers and inserting a special machined metering pin into the centre of the fuel distributor where the top casting is separated from the thin steel plate, we have on a special point the "zero" point. This means that no fuel can enter the top half of these cavities. The pressure is regulated by a spring, washers and piston with an "O" ring on the side of the fuel distributor.
The FUEL PRESSURE and the FUEL FLOW (Fuel Volume) is flowing through the bottom half back to the fuel tank. This means fuel flow establishment. A specially drilled hole which goes from the side of the bottom cavity to the top of the centre pin, and from there to the warm up regulator, eases the flow while the engine is cold. This allows to lift the pin higher as the counter pressure is not so high as yet. This makes the engine run richer while it is in the warm up stage. If the engine is warm, the warm up regulator restricts the return flow to the tank and thereby increases counter pressure to the metering pin. The air sensor plate has now restriction against the applied pressure to lift. This now makes the engine run lean. Now back to the fuel distributor: By moving the fuel metering pin up, this allows the fuel to flow from the bottom cavities to the top cavities. As the top cavities do not have a pressure relief valve, this makes to bend the thin steel plate downwards, and the fuel can then enter in to the injector discharge hoses.
The PRESSURE and FLOW play now the role of being discharged from the injectors. The injectors become now in terms as PRESSURE and FLOW relief valves to cope with a high amount of flow. Press F8 for more fuel distributor information.....on your INTER-JECT supplied computer disk. Fuel distributors and its associated components are for most mechanics not to be opened.
FULL STOP! You never will be able to put them back to getter if you do not have the testing tools which can test FLOW from 10-180 l/h and a separate flow meter to register flow from 2 - 25 cm/min for warm up regulators and as well a pressure gauge to register from 0 to 800 kpa. Be aware, there are in your opinion no serviceable parts in fuel distributors as well in warm up regulators. This door will be closed for you, until you have the right instruction from INTER-JECT, how to re-calibrate warm up regulators to compensate a piston ring wear of an old worn engine. As well to install new " O " rings in fuel distributors and set the correct system and rest pressure.

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google translation nele!!!

THE WARM UP REGULATOR is a small aluminium casting, mainly located near the engine block, the hottest spot in the engine environment. There are four different types of warm up regulator. The first one is just a thermally heated regulator which rellies only on engine heat and is mounted on the engine block. The second one has a heating element internally which is operational via a cable connector and connection from the ignition. The third type is the same as the second one, but has in addition also a vacuum hose connection to the regulator to keep more counter pressure to the centre metering pin if there is no vacuum if the engine is on full load. This stops the backfiring into the manifold by sudden acceleration. The fourth version is the latest which is magnetically controlled via the oxygen sensor and temperature coolant sensor. This warm up regulator is not as such like the others, but is changing the counter pressure via the computer due to the engine load factor, rpm factor, timing factor, oxygen sensor results, and throttle body position. This unit is no longer fitted onto the engine block but, instead, onto the fuel distributor itself. Due to this very complex and bulky unit a special pressure regulator has been fitted into the fuel line near the fire wall. Cars which have this system, I think you would not be able to afford these, as the price tag is way over the $100,000 mark. What's the warm up regulator's job? Please see in Fuel Distributor section for explanation...... The warm up regulator is the kidney of the whole system which makes the engine run properly when it is cold. However, if the engine runs lumpy when it is cold, you know and I know, the warm up regulator is out of calibration to the worn engine and needs re-calibrating with our flow meters.
THE SYSTEM PRESSURE REGULATOR, as described in FUEL DISTRIBUTOR is just as important as the warm up regulator. The only difference is the system regulator opens up at a pressure of 500 KPA or 5 BAR, if the pump delivers 8-9 BAR this means we have 3-4 Bar over pressure,
What happens to the rest of the pressure and flow? Oh no, the engine is not running! We still have to account for 1 to 2 Bar pressure and flow. Yes, it is the counter pressure which flows through the warm up regulator. So 2 Bar is flowing through this regulator with a flow of say 20 l/h and if the engine warms up we will have 3 bar counter pressure towards the metering pin, and a flow of only 10 l/h towards the fuel tank, where by the system pressure discharge increases, not in pressure, but in flow only. The set system pressure is 5 bar. Set is set! Just what has changed is the flow. Go on, measure it with your flow meter, if you have one, and see how cleverly this system works. The location of the system pressure regulator is in the fuel distributor, somewhere on the side. On some models it may be fitted on the top half of the casting, or on other models on the bottom half of the casting.
As we have learned in the fuel distributor, system pressure, and warm up regulator sections, the whole K-JETRONIC system is entirely controlled by pressure and flow. Is this a very clever system in relation to EFI? Yes, I personally say it is the best system in the world, as this is a step towards harnessing pressure and flow, to make each on its own aware of the working potential, to get a result of things happening which can not be seen. The same thing as, for example: RADIO WAVES or X-RAY, you can not see, but you can test this with the right tool, as, say a frequency counter. Things which you can not see, but they are there, the intangibles need the right tools.
As we know, there is a need for all mechanical workshops to have the right diagnostic and servicing tools to cope with the new technology. More so, if we look at a newly printed article from the Service Station Magazine, in the September 1992 issue. They still insist on using a gradient test beaker for a fuel volume test! To do so, the hose from the end of the system pressure regulator must be disconnected and with a new piece of hose extended and used for the volume test. Try to do this on K-JETRONIC or any EFI car. Firstly, you do not know all the different volume readings which are correct on different car types and models. Secondly, any flow discharged after the pressure regulator will have an extreme amount of aeration (air bubbles) and still you have no way to check a flow between the metering pin and warm up regulator, as you can not put the hose in open air. This must be a closed loop to be satisfactorily tested, otherwise the engine will not run, as there is a total pressure loss. Do not forget that the warm up regulator only bypasses limited fuel FLOW back to the fuel tank which can be only measured with the INTER-JECT flow meters, as they are connected into a closed loop
The general fuel flow must be in the 100 l/h range or higher which is colour coded "green". Any medium blocked fuel filter can reduce the fuel flow into the 80 l/h range, which is colour coded "yellow". Faulty fuel pump or severely blocked fuel filters can restrict the flow to 60 l/h or below, which is colour coded "red". This means at this point that there is an indication of a severe fault. This colour coding on glass flow tubes is on system flow tubing. The colour coding on injector flow tubes is "red" at 15 cm3/min which means the injector flow is too rich on idle. The other colour coding is "green" at 10 cm3/min which is the drop point of the indicator to be in the lean area of any four cylinder car.
Please remember that K-JETRONIC systems are only fitted into very expensive cars which have a very high price tag. Just to mention some models; VOLVO, MERCEDES, AUDI, SAAB, BMW, PORSCHE. Just to damage some or only one component may cost you, or if you talk your way out of a paper bag to the customer, he or she may be up for big $$. So rule No 1 is, if you do not know anything about K-JETRONIC leave it as it is, or redirect this job to someone else who has the know how and the testing and servicing tools. As there are different types of K-JETRONIC on the market, which ranges from K-JETRONIC I, II, III, IV, V. The latest model is K-JETRONIC (5) which is installed in MERCEDES BENZ and PORSCHE with OXYGEN SENSORS. The overall principle is still the same, except the counter pressure is controlled by an electro magnetically field, or to explain better, pulse duration's which change counter pressure in the fuel distributor for the oxygen sensor requirements as well as other sensing components. The warm up regulator is no longer installed in this type and is taken care of, from the magnetically correction unit which is fitted on the side of the fuel distributor. This unit receives continuous (HF) HIGH FREQUENCY correction impulses from the control unit, known to us as the " COMPUTER ". The COMPUTER receives correction current flow from those semi components like oxygen sensors, coolant sensor, and many more, to stabilise the best and correct counter pressure to the fuel metering pin. All this may sound to you like UNIVERSITY stuff, yes it is now going that way and only YOU will share prosperity in your business. Think about the challenge in front of you, to be able to repair K-JETRONIC 5, is now open for you. But before you do.... make yourself familiar with the older stuff which is in the past. Think what will happen to all the other mechanics? They will never be able to understand 20% of my write up and it may be for them, that the technology will just overtake their knowledge to an un-recoverable stage. The result is " go out of business ".

lexx, por favor espere eu acabar de postar tudo, depois, se vc quiser, pode traduzir via google, mas corrija a tradução das 17 páginas OK?

em tempo, o texto foi escrito por Leo Karnauchow, holder of the GERMAN master degree in - EFI and K-JETRONIC FUEL INJECTION SERVICE, DIAGNOSTICS, RE-CALIBRATIONS, AND REPAIRS. INTER-JECT Ballina NSW

ANY ENGINE WHICH IS FITTED WITH K-JETRONIC will develop at any stage a poor idle while the engine is cold. You now know where the problem is. There may be the problem of restricted flow from the fuel warm up regulator, which may develop restricted flow due to dirt or is out of calibration due to the worn engine (compression loss). But do not be too sure before you jump horses. First to basic, and I do not have to repeat myself over again. The best and quickest confirmation to yourself and to your customer is as follows; remove the air bellow (HOSE) or air filter on the top of the air sensor box. Start the engine and press the sensor plate gently downwards. Can you feel the counter pressure against the sensor plate? Just press it a bit more and see the engine become very smooth in idle. Now I ask you what is wrong?? You still point your finger at the WARM UP REGULATOR. I tell you, you are wrong in one way, as you have not done 3 simple checks.
They are:
1. Check compression on each cylinder, this may lead to the loss of air flow via sensor plate which can not be lifted or pressed down far enough.
And this is probably the simplest check: Check the bellows next to the throttle body, particularly in the area where the piping that leads to the Auxiliary Air Valve, the bellows on the fuel distributor, and other intake air piping for cracks as any air leaks will cause a lean condition resulting from un-metered air entering the manifold. These can be adjusted out, but if they are discovered later, could cause a dangerous condition (backfiring, etc) if the system is not re-adjusted. I've learned this from both a 1978 VW Scirocco (K-Jetronic) and a 1981 VW Scirocco (KE-Jetronic O2 sensor equipped). $400.00 (U.S.) for parts / troubleshooting by a mechanic (on the '78), and it was solved with less than $100 by myself when he couldn't figure it out. (Above paragraph has been sent in by Mr. Kirk McGehee)

2. Check if the fuel pump has been recently changed with the right type and same brand, you can see if it is new on the housing.
3. Check with the right tools now the fuel FLOW and PRESSURE on the fuel pump. Check the system FLOW and PRESSURE as well and the resting pressure. Connect the servicing unit between the warm up regulator and fuel distributor for correct regulator operation pressure and flow changes. The last thing you may not be able to do, re-calibrate the warm up regulator to a lower counter pressure, as a special training and bench work is involved, and you must register yourself for a K-JETRONIC repair course with our training manager Leo Karnauchow in INTER-JECT Office Ballina NSW.
THE ENGINE WILL RUN SMOOTHLY, after it has been warmed up. This is a sign of warm up regulator fault.
1. Out of calibration to the RICH side (too far open) must be reset by trained personnel only.
2. Out of calibration to the worn engine (higher counter pressure against the metering pin). This causes the cold engine to run very lean. A new warm up regulator will only do very little as the sensor plate still has not enough air flow to be lifted high enough.
3. Warm up regulator restricted with dirt or blocked or faulty in the electrical circuit. Remove the hose from the regulator towards the fuel tank and check for fuel flow. Use test light or ohm meter for continuity check in the heater wiring circuit or plug.
A BACKFIRING FROM THE INLET MANIFOLD, towards the air sensor plate, can have a devastating result of damage to the air sensor plate arm. There is, in the air accumulator, a rubber stop which may give way if heavy return pressure force is against it. This can then interfere with the previously set mixture setting. The engine may then run very lumpy or not at all. The reason for backfiring in the first instance is too lean a fuel mixture on acceleration, plus a very high counter pressure to the fuel metering pin. Car manufacturers have prevented this from happening by using an updated warm up regulator with a vacuum adaptor. This will now in terms change the main principles, regardless if the engine is warm or cold. The centre counter pressure will only then increase in loss of vacuum, which lets the tension spring go free to be able to restrict the outlet flow of the warm up regulator to increase the counter pressure. If the engine is on idle, there is high vacuum to the diaphragm in the warm up regulator and the tension spring has been pulled back to increase the flow and drop the counter pressure. Vacuum assisted warm up regulators take the flat spot, backfiring and hesitation away from any modern car. This makes the airflow in the manifold lift the sensor plate higher to make the car run richer while on idle. Leaner, as more air flow passes the gap of the sensor plate, which lifts the sensor plate higher, but at the same time the counter pressure starts to build up to work against the metering pin which adjusts the fuel mixture to a leaner setting. The vacuum assisted warm up regulator is now compensating for more counter pressure as the vacuum loss gradually increases.
RPM LOSS ON HIGH SPEED is usually fuel related. This can be simply found with the INTER-JECT LB-291/F or 2F. First check the main fuel flow, which must be between 120 to 140 l/h with a system pressure of 5 bar (checking point is fuel distributor and fuel inlet line). If the fuel flow is only 40 or 80 l/h, change the fuel filter and check again. If there are no changes after the fuel filter has been replaced, remove the lift pump and check the fuel-sock for any softness or if it has been sucked in together, which restricts the fuel flow. This causes the pressure pump to be extremely noisy as it works in a vacuum suction situation. A spring will keep the sock apart for a larger area to suck more fuel through. Check fuel lift pump for flow only and also the main pump for flow and pressure. Most important, make sure the fuel tank is at least 1/4 full, as the fuel rushes to one side of the fuel tank when you are cornering the vehicle. This makes the pump only suck air and the engine will lose rpm. Check the fuel tank for WATER, and water in the fuel distributor as well. Water can be only removed with the INTER-JECT LB-288/4 as this unit will run the engine on its own with the fuel tank disconnected. Or now the LB 291/2F equipment with the original car fuel pump in action where chemically, the water will be removed with INTER-JECTRON. (INTER-JECT'S own designed and developed chemical with colour fault indicators).

PRESSURE SETTING, while the engine is running must be 500 kpa or 5 bar. However, if the fuel pump has been changed with a different type than the original has been, the pressure could be higher or lower as it depend on the fuel flow. Still, whatever it may be, fuel flow or pressure, the setting must be 5 bar. Remember, low fuel flow makes a very slow pressure recovery. High fuel flow makes a very quick pressure recovery with no pressure loss, as the fuel pump flow is still higher than the system pressure setting. So, if you have fuel flow of 140 l/h, this makes a very quick pressure build up which may be 5.2 bar. Because of this higher fuel flow, we call this pressure ACCUMULATION. There is no time for pressure to settle as the high fuel flow overrides and queues up higher pressure before the pressure release valve. On the other hand if we have only 120 l/h fuel flow, the pressure in the system would be exactly 5 bar. If you would adjust the system pressure which has a reading of 5.2 bar by a flow of 140 l/h to exactly 5 bar, so your flow would increase from 140 l/h to 152 l/h and this is exactly the right result. SO, the LOWER THE PRESSURE the flow increases. So the higher the pressure, FLOW DECREASES. [Explanation] So your system pressure is set exactly to 5 bar when the engine is 'COLD'. Some fuel flow and pressure is also flowing via the warm up regulator. Why does this warm up regulator flow and pressure not show up in the system pressure setting difference will be a slight increase in the fuel FLOW as the engine becomes 'WARM OR HOT'. The fuel flow increase is only 2 - 3 l/h which is not significant to change the system pressure to a higher reading. Therefore, you and I know that the right type of " FLOW METERS AND PRESSURE GAUGES " are essential for K-JETRONIC and E.F.I. vehicles. It is required to connect the service flow meter and pressure gauge between the fuel distributor and fuel supply hose to check for SYSTEM FLOW and SYSTEM PRESSURE. No fuel leaks are permissible on connecting points. Next, if you suspect a faulty warm up regulator, or the possibility that it is out of calibration, which most of them are. Connect the service FLOW METER and PRESSURE GAUGE only when the vehicle is cold, between the ' CENTRE FUEL DISTRIBUTOR OUTLET ' and the ' WARM UP REGULATOR INLET '. This allows you to measure the correct warm up FLOW and increasing C o u n t e r P r e s s u r e as well as decreasing flow, while the engine is running. If you connect the service unit between the fuel distributor and return line, the fuel pressure will be very low. The narrow size of the fuel line causes fuel ACCUMULATION or PIPE FRICTION that the pressure gauge reads some pressure. On the other hand the fuel flow would be just above 10 l/h higher, as we have the warm up regulator flow joining into the same return line. If you disconnect the center counter pressure hose from the fuel distributor, the result is total loss of system pressure, holding pressure and accumulator pressure. In other words, the car won't start.
THE MOMENT YOU switch the engine off while the FLOW and PRESSURE GAUGE is connected in series between the fuel distributor and fuel pump pressure side, the gauge will drop to a resting point. In most cases it is a reading above 200 kpa or 2 bar. Never less! This is caused as the system regulator valve shuts approximately at 4.2 Bar. However, a bleed off of fuel via the warm up regulator will bring the resting pressure to 3 Bar or a minimum of 2.2 Bar as the compression spring in the warm up regulator shuts off the inlet piping. This causes resting pressure in the fuel distributor. If p check for a system leak. INJECTORS ARE THE LAST TO BLAME FOR LEAKS, so please remember. Injectors in K-JETRONIC play the role strictly of DEPRESSURISING VALVES, that's all they are !! For total system pressure loss, there are only 2 main items to check.
1. The check valve or one way valve in the fuel pump is faulty.
2. The 'O' ring on the system pressure relief valve is leaking.
Secondary checks:
1. Fuel line is leaking somewhere on joints.
2. The fuel accumulator diaphragm has a small pin hole and is dribbling out from the safety discharge pipe.
THE FUEL ACCUMULATOR, OR BETTER KNOWN IN AUSTRALIA AS FUEL DAMPER, is located just after the fuel pump. So it's location is between the fuel pump and fuel filter. All K-JETRONIC systems must have this very important component fitted into the fuel supply line. The housing of the fuel accumulator is split into two parts, the same as the fuel distributor. The difference is that the top part houses a very heavy compression spring, and as well, it has a safety fuel bleed outlet or, in other words, atmospheric discharge opening. The joining point to the bottom half is a metal folding lip and houses a heavy duty diaphragm. The bottom part has internally a metal fuel deflection plate, where the inlet fuel line is connected to a metric fitting. The fuel outlet is then taken off from any part of the bottom housing, as well from a 14 mm metric fitting. The exact location of the fuel accumulator is as close as possible to the outlet of the fuel pressure pump, or main pump. This will inhibit any fuel pressure noises from the fuel pump. As we have learned, the relationship between fuel flow and fuel pressure, are constantly changing. The fuel accumulator will now assist in keeping the pressure and flow in the fuel distributor bottom half always the same. The fuel accumulator now has the ability to take into itself the reserve pressure and flow from the fuel pump. Due to the long fuel line to the engine bay, known as fuel pipe flow friction and the system pressure regulator valve in the fuel distributor head, this keeps the diaphragm of the fuel accumulator compressed and therefore stores more fuel while the pump is running. By acceleration, some of the fuel FLOW AND PRESSURE will enter the top half of the fuel distributor, which can only go ONE WAY to be discharged by the injectors. The diaphragm in the fuel accumulator can now compensate for the fuel diversion to the injectors, or fuel diversion via the system pressure relief valve. The fuel accumulator also plays the role of controlling the fuel flow ' back up '. Either to the injectors or via the system pressure valve.

K-JETRONIC INJECTORS are, in general, serviceable. You can flush them with a pressure setting of more than 4 bar and as well back-flush the injectors by keeping the pintle open with a special locking tool. To understand K-JETRONIC injectors properly, you must see the purpose; why they're in a motor car and the way the injectors work in a pressure/flow principle. As mentioned before, the injectors are only depressurising valves. No electronics or magnetic coils drive these injectors. Only FLOW and PRESSURE changes drive these precision depressurising valves. For example, the diesel engine injector has a very close similarity to the K-JETRONIC injector. The only difference is the pressure variation. Diesel injector needles are lifted off the seat only by extremely high pressure with very, very low flow. K-JETRONIC injectors are pushed open by medium pressure with variations of flow and pressure. A return spring with medium tension keeps the injector pintles closed to stop fuel dribbling into the manifold. Each injector, depending on the type of engine, has a main seal to stop air leaks into the manifold. Other types have a bakelite (it is a type of very brittle plastic but heat resistant) cone seat and 'O'ring as well, which are bolted onto the manifold (VOLVO). The quickest way to clean K-JETRONIC injectors, is to remove them from the manifold. Use a wire brush, driven by an electric motor, and brush all the carbon from the injectors. Clean the pintle side as well with the wire brush. Soak all injectors in an ORGANIC SOLVENT SOLUTION, the best is INTER-JECT CLEANER, BLUE, or INTER-JECTRON which definitely leaves all other mineral, hydrocarbon oil based injection cleaners on the market, totally as a foolishly invented joke that remain as an end user "rip off". After soaking for 30 minutes, use compressed air, blow through the injector, listening for the distinctive resonating pressure sound. Repeat this 6 times per injector, with a bit of liquid filled each time into the back of the injector. Look for the initial spray pattern at the beginning of each air blast. The filter basket in the injectors can not be removed, however, with a special small tool, the pintle can be locked into an open position and thereby the injector can be, with a different pressure setting, back-flushed to clean the filter basket backwards. Each time the injector has been removed from it's seat, the SEAL or 'O' ring has to be checked for possible hardness or damage, or, if necessary to be replaced. A plastic insert inside the injector, which keeps the small compression spring behind the pintle cone under specific set pressure, may melt and restrict the flow and spray pattern via the offending injector. This happens mainly if the engine has been overheated. (Head gasket leak and coolant loss in the radiator). If this happens, do a flow test into graduated test beakers while all injectors are removed, but still connected onto the fuel lines. If one or more injectors play up in the flow test, swap these injectors with good flowing injectors to the same fuel lines from the fuel distributor. If these become good and the others bad, exchange or repair the fuel distributor as the internal seals have been blown to those injector fuel lines.
K-JETRONIC fuel pumps are certainly different to E.F.I. fuel pumps. Firstly, physically they may be larger, as they have a larger roller/pressure chamber, which still can vary in difference from a 4 cylinder car to a V8 Mercedes Benz car. K-JETRONIC fuel filters are as well larger than E.F.I. filters. The fuel flow of a 4 cylinder Volvo must be in the range of 140 l/h by a system pressure of 500 kpa or 5 bar. To check the fuel flow of the same vehicle, but this time the real flow from the fuel pump without any pressure, would run the flow meter off the scale. The approximate reading would be 250 l/h. Now to connect the fuel pump to a pressure source, like a fuel distributor of 500 kpa or 5 bar, this will slow down the fuel flow just to 140 l/h. So you can see the relationship between flow and pressure. All this can confuse any mechanic at any time and therefore a proper schooling in K-JETRONIC is extremely ESSENTIAL to be able to work confidently on these injection systems. Also, you must sooner or later invest in INTER-JECT flow meters and calibrated pressure gauges, as you can not afford to be without them, and losing on business.

POLYTHENE HOSES, or metal piping, to and from the fuel distributor, have been fitted in all K-JETRONIC systems. Their main purpose is to prevent hose or fuel line expansion, which may burst the fuel line and would be a fire hazard to the vehicle. The safety requirements are that any fuel supplying line must have a bursting point of at least 30 bar. Metal lines are better for holding pressure, but are disadvantaged in line flexibility. This means that on any MERCEDES BENZ, the fuel injectors are connected to metal lines which are very fragile in bending and awkward when the injectors are removed from the manifold with the lines connected for flow test purposes. There is only one way out, which is keeping a spare set of polythene lines with fittings in the workshop which can be quickly exchanged for test purposes. Polythene hoses are made from a type of hard plastic which is fuel and acid resistant. Some vehicles also have some kind of heat shield over the polythene hoses which may only be a rubber hose sleeve. The injectors can be very easily removed from the manifold while connected to the lines for flow and volume tests. Remember; never cut these hoses anywhere you may decide to connect a pressure and flow meter between them. Rule No 1: always use the fitting connections by un-doing them and join other connections in series for the testing equipment. Also, be aware that, as K-JETRONIC has only been manufactured in Germany, the fittings are in "METRIC", made to DIN specification of thread pitch requirement which should be INTERNATIONALLY known. The common cars which have polythene hoses include BMW, PORSCHE, VOLVO, SAAB and some AUDI models. Metal piping is found in all MERCEDES BENZ models and in some late model AUDI's.

YES, POLYTHENE HOSES can be repaired quite easily. The only thing you need is a special tool you can make yourself, which enables you to clamp the polythene hose into a vice so you can knock in any fitting which has a barb holding it into the hose with a rubber hammer. If the hose has been kinked, it is advisable to change it, as the point of the kink may burst under pressure, and it can restrict the flow which can build up higher pressure to the pump side. If the injector hose between the injector and distributor has a kink, it must be changed, as a flow restriction to the injector may put the engine out of balance. Where can you buy these hoses? In any HYDRAULICS outlet, on rolls, in different sizes. To make the tool which is used for clamping the hose end into the vice, use an aluminium block, say 8 cm long x 5 cm high and 3 - 4 cm thick. Drill through the 3-4 cm thick side a hole which is just a tiny fraction larger than the hose. The hole must be drilled from one side right through to the other side of the aluminium block. Then, with a hacksaw, cut the aluminium block in half, so that you have cut the drilled hole into two halves. The poly hose will then fit exactly between the two halves of the block, in the drilled channel. Let about 10 mm of the poly hose protrude from the aluminium block and clamp the block into a vice. Because of the hacksaw cut, the drilled channel is now the same size as the hose. This keeps the hose very firm in the vise. Then use the required fitting and hit it into the hose with a rubber hammer. Keep this tool, INTER-JECT's own design, for later use.
Picture plan for this tool you find in the Data pool or in your Free Computer Disk update to download inside from the Data pool.

COLD START INJECTORS are also found in some EFI vehicles. Just about every K-JETRONIC system has a cold start injector fitted into the air manifold. These injectors are activated for only approximately 7 to 8 seconds from the starter motor via the thermal time switch (see "THERMAL TIME SWITCH" section for more information). Cold start injectors are electro-magnetical solenoid valves, with a fine fuel spray due to the 5 bar fuel pressure setting from the fuel distributor. There are variations of cold start injectors for all different engine sizes and models. As mentioned before, banjo type fittings are used in conjunction with polythene hoses for safe and leak proof connections. The location of this injector varies in different vehicles. The BMW 3 and 5 series has the cold start injector fitted under the manifold. To get to the injector, the car must be lifted by hoist. Other cars have this injector fitted right in the middle of the manifold. On EFI CARS, like the Toyota Camry or Mazda, this injector is clearly visible. On K-JETRONIC cars, it is the same on the AUDI 5+5, 80, 100, and right throughout the Mercedes Benz model range, except for the 560SE and SL. Press F8 for cold start injector information . . . . . .
The THERMAL TIME SWITCH is a timing device used to control cold start injection to a time limit, to prevent possible engine flatting from excessive fuel. The operation or activation of the thermal time switch is via the starter motor for approximately 7-8 seconds, and secondly, the temperature of the coolant in the engine near the thermostat. The warm or hot coolant stops any activation of the cold start injector until the coolant temperature drops to 25 degrees centigrade. Below this temperature, the starter motor only can activate the injector again 8 seconds. There is only one chance given to you to test the current flow from the thermal time switch. After, you must wait for at least 5 minutes for a new current test. As soon as the contact points are open, the earth from the cold start injector is taken away. The injector stops injecting fuel. By warming up the engine, the coolant temperature keeps the contact points from the thermal time switch open, regardless of whether the starter motor is activated or not. The coolant temperature overrides all previous operations for any possible cold start injector activation while the engine is hot. It happens on many occasions that the contact points or the heating element on the bimetallic strip are melted together or burnt off. This is caused mainly from jump starting. An external battery connected to the faulty internal battery in series instead of parallel, which is 24 volt, will cause this melt down of the thermal time switch. The result is continuous cold start injection each time the starter motor is activated. The engine is flooded with petrol and cannot start. The reason for this is that very thin cable is used in commercially manufactured "JUMPER LEADS" which forces the car owner to connect in series to make the engine turn over. Should, under any circumstances, the oil level in the engine sump be higher than normal (this applies for all vehicles with cold start injectors fitted) check the oil for fuel dilutions. In most cases, each time the thermal time switch comes to a closed point position while the engine is stationary and turned off, it injects the resting or residual pressure into the manifold due to a static current in the computer as the computer may have bad or no earth on most EFI cars. With K-JETRONIC, the 'PLUS' cable from the battery is always under load to the starter motor. Dirty starter solenoid contacts may let pass 4 to 6 volts to the cold start injector and load it up with positive current. The closed contact points in the thermal time switch give an earth circuit, which activates the cold start injector for complete pressure drop from the fuel distributor into the manifold. My advice is to put your fingers onto the cold start injector to feel if it is warm as the engine is cold. Be extremely suspicious even if the injector is only slightly warm. Disconnect the fuel line from the cold start injector and check fuel pressure. Remove the cable from the cold start injector, check for current flow with a digital volt meter.

SO YOU HAVE TOTAL PRESSURE LOSS! The quickest way to find out in which direction the fuel distributor has pressure loss is to disconnect the fuel return line. Use a small container to catch any fuel lost from the system pressure regulator outlet (return line connecting port). Disconnect the return line from the warm up regulator, the joining point from the main return line. See if there is a steady petrol flow. If not, use a small container to catch any fuel loss. Finally, disconnect the cold start injector fuel line after one hour. Check if there is any fuel in the fuel catching containers (return outlet and the return line from the warm up regulator). By disconnecting the pressure line to the cold start injector, if no, or a very small amount, of fuel pressure is noticeable, then change the CHECK VALVE in the fuel pump. Check at the same time for an accumulator leak from the air bleed, and a fuel line leak on any joint. If you have a continuous leak from the return line connection port or any fuel accumulation in the container, then change the seal on the system pressure regulator valve. If you have continuous flow or a dribble from the warm up regulator return line, then change the WARM UP REGULATOR. If you have the INTER-JECT LB-291/F or 2F, open up the regulator and remove the rust spot, dirt or corrosion spot under the counter pressure inlet or outlet side. Use the INTER-JECT tool for a successful on car or off car re-calibration on the warm up regulator. Lastly, if you do not find any fault in any of those items, please refer to the "THERMAL TIME SWITCH" section of this menu . . . . .
THE AUXILARY AIR VALVE, or air slide, is found in every car fitted with a cold start injector. This also applies to EFI cars. This air valve consists of a full aluminium body encasing a bimetallic strip which changes its structure if heated. The heating element is in the centre of the bimetallic strip. The ignition supplies the power to the heating element. The bimetallic strip is connected to a metal disc with a small cut out for the air to pass through. A return spring keeps this metal disc somewhere near the "adjusted" resting point for a bigger opening to let more air pass through when the engine is cold. Hose adaptors on each side of this air valve keeps a very tight seal which prevents an airleak from the throttle body to the manifold. How does this air valve work? It is an improved version of the "CHOKE" we know in carburettor cars. The working principle of this air valve, as the name says, "AUXILARY AIR VALVE", is that it passes more air directly to the manifold when the engine is cold. The air will be drawn in before the throttle body via this valve and directed into the manifold. In other words, more air can by pass the throttle body which lifts/lowers the air sensor plate for enrichment and higher rpm's of the engine, as in EFI cars, where the vane airflow meter or any other sensing device will be moved for more enrichment and higher engine rpm's. The ignition is heating the heating element constantly. The bimetallic strip slowly changes its own structure (TURNS or BENDS) which moves the slotted air passing plate to a lower/slower airflow. Known as "AIR FLOW RESTRICTION", this will gradually slow down the engine rpm and the engine becomes leaner. This is also known to mechanics as "AIRSLIDE" as this is the way this component works. Can this auxiliary air valve go out of calibration? YES, it will become lazy or even inoperative, when the engine encounters piston ring wear. This applies to all EFI or K-JETRONIC vehicles. Test the heating element continuity, and if the circuit is open, change this auxiliary air valve for a new one. If the circuit is closed, you can adjust the slide disc by loosening the yellow painted adjuster screw. Move the slide disc with a screwdriver to a more open position and lock the adjuster screw. Remember, the air auxiliary valve must be cold for correct adjustments. The location of the air auxiliary valve is sometimes in a very inaccessible position, as in Toyota EFI vehicles or BMW's. The Mercedes Benz air auxiliary valve is a completely different type, as it is warmed by the coolant. A mercury type filled insert in the housing expands to change the air by pass to the manifold.

EVERY FUEL INJECTED CAR has some type of check valve (NON RETURN VALVE) fitted externally or internally in the main fuel pump. This allows the flow to go only ONE WAY, towards the fuel distributor. The system pressure setting in the fuel distributor keeps holding pressure in the system and fuel line to the fuel pump. A special fitting on the pump has an internal small plastic/stainless steel ball and a compression spring, which punches the ball against the fuel discharge opening of this fitting. The whole fitting with is contents is called a "CHECK VALVE". Check valves can sometimes not seal properly, due to corrosion or build up on the steel ball. Plastic ball check valves tend to distortions due to their plastic properties, becoming like a four cornered ball. This happens mainly from fuel friction of FLOW and PRESSURE and the rising temperature of the low fuel content in the fuel tank. Water in the fuel speeds up corrosion to the compression spring which may completely disintegrate. The sealing ball goes in every direction which can block or restrict the fuel outlet from the fuel pump. The final result of this is total loss of system pressure. The car becomes extremely hard to start in the morning. This also applies for a car which has driven for more than 10 km. A restarting of the engine is almost impossible, as vapour expansion in the fuel distributor from the hot engine pushes the fuel totally back into the fuel tank. To attempt to restart the engine, due to this temporary air lock in the fuel line and in the fuel distributor, will almost drain the battery.

THE CHARCOAL CANISTER is a tank ventilation unit in a closed loop from the fuel tank towards the vacuum source of the engine. Due to the anti-pollution legislation, all cars must now be fitted with a single or dual stage charcoal canister. HC, or fuel fumes must not enter the atmosphere. Instead they will be sucked off into the engine's intake manifold via a purge valve on the charcoal canister. If the fuel tank slowly becomes empty, the vacuum from the fuel tank sucks air back into the fuel tank via the purge valve from the engine manifold, to replace the fuel used up. The purge valve is a pressure or vacuum equaliser, operated by a diaphragm and seals. The charcoals in the canister is used as a filtering compound for liquids like petrol, and air. Petrol may enter from time to time when the fuel tank is over filled and the vehicle is left in the sun on a hot day. Fuel will expand and follow the breather line into the charcoal canister. On rainy days the overall humidity is about 98% which passes via the filtrations of the charcoal canister back to the fuel tank. The continuous moisture filtration over the years makes this unit internally look like an engine with a severe head gasket leak, with grey slime inside the tappet cover. This brings the charcoal canister out of service for tank ventilation. Excessive vacuum build up inside the fuel tank will restrict the fuel flow and pressure. By removing the fuel cap, a big air suction or air pressure from or into the tank is the result of a blocked tank ventilation which may also be caused by a kinked vent line to the charcoal canister. Checking the charcoal canister operation is quite simple with the INTER-JECT LB-291/F or 2F. Connect the servicing instrument in series into the pressure supply line. Close the diversion valve and start the vehicle. Use a 20 litre container, connect a diversion hose to the valve outlet and insert the hose into the 20 litre container. Open the diversion valve to a point of 40 l/h on the flow meter indicator. See if the flow changes to 35 or a lower indication before the 20 litre container becomes full. Remove the tank ventilation hose from the charcoal canister and at the same time see the flow increase on the flow meter which returns to 40 l/h. The service instrument is talking to you; CHANGE THE CHARCOAL CANISTER as it is blocked.

Fass,

obrigado.

O John vai ficar p da vida, pois odeia o idioma ingles.

Agora tradução do google?

esta eu quero ver

Alan,

Nada contra o idoma anglo. Pelo contrário! Eu achei muito interessante o artigo, mas acho mais interessante ainda, um breve resumo no idioma do país em que vivemos, pois desta forma as pessoas lerão algo mais sucinto, o que poderá acalorar a discussão do tema ainda mais!!!

Aíííiií´......Valeu John, obrigado por termos alguem em defesa dos menos esclarecidos culturalmente diga se de passagem referente ao idioma não Pátrio!!! minha esposa é professora de ingles....mas eu como sou Nacionalista convicto não vou traduzir nem no google e nem pedir pra ela traduzir pra mim....vou esperar um resumo suscinto em nossa lingua para começar a me inteirar do que se trata. Parabéns tb ao Fass pela iniciativa e pelo conhecimento.

caro Lexx, nacionalista também sou, quase extremista. Porém esclareço a você e ao John, tive necessidade agora de ter um conhecimento do assunto, visto que resolvi dar uma de Allan e desmontei o sistema da minha. E só consegui remontar graças ao carinho do maluhy. Hoje está funcionando como antes, depois de 28 dias de briga. Pesquisei bastante na internet sobre o assunto, juntei o que já tinhamos aqui, em suma umas 40 páginas impressas sobre o assunto e usei o tradutor google. Quando fui ler, tive que voltar à lingua original pois a tradução é comercial e não técnica, deixando o texto incompreensível. Esse fim de semana deparei com esse texto, australiano , que foi o mais completo e preciso que achei. Sou curioso e estudioso, vou atrás.
O objetivo de postar foi dar uma ferramenta para quem se aventura como eu e não tem o conhecimento do Maluhy... Não é um texto para leitura simples e sim para estudo e suporte de quem precise e tenha esse sistemas em seus carros, embora livre para leitura, lógico...
Mas vou atenter, quando voltar de viagem farei um resumo, embora ache que vai ficar muito vazio.

2.2.5 – SISTEMA K – JETRONIC

O sistema K-

Fig. 2.16

2.2.5.2 – A BOMBA DE ALIMENTAÇÃO DE COMBUSTÍVEL

A bomba de gasolina é uma bomba de rolos com um débito de cerca de 120 litros por hora, accionada
por um motor eléctrico com rotor bobinado, convencional, onde o fluido combustível atravessa
todo o corpo do motor até sair da bomba.



A – Pequena quantidade de ar admitido, o disco deflector levanta um pouco
B – grande quantidade de ar admitido. O disco deflector levanta mais
Fig. 2.15 – Variação da quantidade de ar admitido em função


Fig. 2.16

Tanto o induzido como o indutor do motor eléctrico, bem como as escovas e o comutador é banhado por gasolina sem o risco de uma faísca, no seu interior, poder inflamar o fluido combustível uma vez que a bomba contém na entrada e na saída, válvulas que permitem que o circuito de combustível se encontre devidamente isolado do ar.
Na periferia do disco rotor há cinco entalhes em forma de bolsa, em cada um dos quais se encontra um rolo.
Sob a acção da força centrífuga, os rolos são empurrados para fora. Devido à excentricidade entre
a câmara da bomba e o disco rotor verifica-se o aumento do volume na entrada e a consequente
redução na saída obtendo-se o efeito de bombagem desejado. Todo o conteúdo interno da bomba, como as peças do motor eléctrico, é banhado pelo combustível.
Graças à falta de oxigénio e aos espaços relativamente pequenos da bomba, não há qualquer
perigo de explosão.


Fig. 2.17 – Bomba de combustível


Fig. 2.18 – Bomba de combustível em corte onde se pode observar o fluxo de gasolina através do corpo da bomba

Duas válvulas de sobrepressão, uma na entrada e outra na saída, interrompem o circuito entre os lados de aspiração e de pressão, quando a pressão, por exemplo, sobe excessivamente, em caso de avaria do regulador de pressão. Uma válvula de retenção permite manter uma certa pressão residual no sistema ao ser desligado o motor.




Fig. 2.21 – Pormenor alargado do regulador de pressão

2.2.5.3 – O ACUMULADOR DE PRESSÃO DE COMBUSTÍVEL

O acumulador de pressão está montado na tubagem de pressão à saida da bomba de alimentação. É uma cápsula constituída por duas câmaras separadas por um diafragma. A câmara da mola e a câmara de cumulação têm três funções a desempenhar:


Fig. 2.22 – Acumulador de pressão de gasolina


1. A partir do momento em que a bomba de alimentação começa a funcionar, a câmara de acumulação enche-se, a mola do diafragma fica sob tensão, o que atrasa, por um curto espaço de tempo, a acumulação da pressão no sistema. Este atraso vai permitir que a pressão se manifeste primeiramente na parte superior do êmbolo de comando do distribuidor / dosificador de combustível, pressionando-o no sentido descendente, se não se encontrar já na posição inicial.

2. Tem como segunda função neutralizar (amortecedor) os impulsos de bombagem de gasolina, por meio de uma haste amortecedora incorporada.

3. Permite manter o sistema sob pressão durante algum tempo, após a paragem do motor, o que reduz a formação de bolhas de ar, garantindo um bom comportamento do arranque em quente.


Fig. 2.23 – Acumulador em funcionamento normal não acumulando combustível


Fig. 2.24 – Acumulador em posição de percurso máximo, enchimento máximo da câmara de combustão

2.2.5.4 – O FILTRO DE COMBUSTÍVEL

É uma peça de consumo (não recuperável) montada entre o acumulador de pressão e o distribuidor de gasolina. É composto por um filtro de papel e um filtro de rede muito fina, que retém quaisquer partículas de papel que tenham podido desprender-se. Ambos os elementos se encontram alojados num invólucro único.
Ao proceder-se à sua substituição há que atender ao sentido de circulação do combustível, impresso na caixa do próprio filtro.

Fig. 2.25 – Filtro de combustível

2.2.5.5 – O DISTRIBUIDOR / DOSIFICADOR DE COMBUSTÍVEL

O distribuidor / dosificador é outro elemento que juntamente com medidor de caudal, forma o já conhecido regulador de mistura. O distribuidor / dosificador compõe-se de uma carcaça dividida em duas metades, separadas por um diafragma de aço.

Fig. 2.27 – circuito de pressão de comando do sistema de injeçcão

O combustível entra primeiro nas câmaras inferiores fluindo em seguida ao longo do êmbolo de comando segundo a posição do mesmo e consequente secção das fendas de estrangulamento para as câmaras superiores. As câmaras inferiores e superiores, o diafragma em aço e a mola constituem as válvulas de pressão diferencial.


Fig. 2.28 – Diferentes estados de funcionamento da válvula de
doseamento de combustível injectado


Estas válvulas de sede plana são introduzidas à pressão na parte superior do dosificador e têm como função manter uma diferença de pressão constante nos estrangulamentos de comando, independentemente da pressão do sistema e do volume de débito de combustível. Esta quebra de pressão é de 0,1 bar.

Se a pressão for igual nas câmaras superiores e inferiores as válvulas são fechadas pelo diafragma. É por esta razão que se torna necessário existir sempre uma certa quebra de pressão de forma a afastar o diafragma das sedes plana. Por isso é montada uma mola helicoidal, rigorosamente calibrada, em cada válvula. Assim o oseamento de combustível fica dependente apenas da secção de abertura dos estranguladores de comando.

2.2.5.6 – VÁLVULA DE PRESSÃO DIFERENCIAL


Posição do diafragma com grande quantidade de combustível a ser injectada. Se ao acelerar, fluir mais ombustível através dos canais doseadores para as câmaras superiores, a pressão ali, aumenta momentaneamente.




Fig. 2.29 – Peças do doseador – distribuidor de um sisterma K-Jetronic

O diafragma adopta uma posição mais côncava, aumentando também a superfície de abertura das válvulas de pressão diferencial, até que a diferença de pressão, que é determinada pela mola (0,1 bar) permaneça constante.
Se fluir menos combustível, o diafragma retoma a sua posição, diminuindo a secção de abertura das válvulas, até que, de novo, a pressão diferencial determinada pela tensão da mola seja 0,1 bar. Todo este processo determina um equilíbrio de forças no diafragma e que mantém, qualquer que seja a carga no motor.
NOTA: O curso do diafragma é de apenas alguns centésimos de milímetro.


2.2.5.7 – O DISPOSITIVO DE ARRANQUE A FRIO


Ao arrancar em frio e por forma a ultrapassar o maior valor de atrito presente num motor que ainda não atingiu a sua temperatura normal de funcionamento, é necessário uma mistura de ar/ gasolina mais rica.
Durante o processo de arranque a baixas temperaturas é activado o dispositivo de arranque a frio que é constituído pelo interruptor térmico temporizado, e pelo injector de arranque a frio.


Fig. 230 – Válvula de pressão diferencial


Fig. 2.31 – Circulação de combustível na situação de arranque a frio

Do injector a arranque a frio não é exigida uma grande precisão relativamente aos períodos de abertura e fecho, dado ser comandada pelo interruptor térmico temporizado, através do relé durante o processo de arranque.
O que interessa principalmente é haver uma pulverização muito fina e esta obtém-se fazendo passar o combustível pela sede da válvula, ao longo do induzido, através de dois orifícios, um transversal e um longitudinal para o pulverizador rotativo.
No pulverizador, o combustível é posto em rotação por dois furos de entrada tangenciais, deixando o combustível perfeitamente atomizado sob a forma de um cone de 90º.


2.2.5.8 – O INTERRUPTOR TÉRMICO TEMPORIZADO

Quando se arranca um motor frio, fornecese tensão ao injector de arranque a frio e ao interruptor térmico temporizado através do interruptor da chave de ignição.


Fig. 2.32 – Injector de arranque a frio


Fig. 2.33 – Interruptor térmico temporizado

Se o processo de arranque demorar mais de 8 a 15s, o interruptor térmico de tempo desliga o injector de arranque a frio evitando-se assim que o motor se “afogue” em combustível. Neste caso o interruptor térmico temporizado desempenha a função de comando do injector de arranque a frio.
Quando a temperatura do motor estiver acima dos 35ºC, na altura de arranque o interruptor térmico temporizado já terá aberto a ligação para o injector de arranque a frio deixando este de injectar combustível extra.

2.2.5.9 – A VÁLVULA DE AR ADICIONAL

Esta válvula permite a passagem de ar em derivação à borboleta durante o arranque a frio e na fase de aquecimento. A secção de passagem é comandada por um disco em contacto com uma mola bimetálica que é aquecida electricamente.
Em frio está aberta a secção de passagem máxima que vai fechando gradualmente à medida que o motor aquece. Está montada num ponto do motor característico quanto ao processamento da temperatura.


Fig. 2.34 – Válvula de ar adicional

2.2.5.10 – O REGULADOR DA PRESSÃO DE COMANDO

O regulador da pressão de comando regula a pressão de comando que actua no topo do êmbolo do dosificador, em função da temperatura e da pressão no colector de admissão.
A caixa deste regulador contém um diafragma que está posicionado entre o canal de pressão de gasolina vindo do dosificador e o canal de retorno de combustível ao depósito. O diafragma está sob tensão de duas molas, através de uma cavilha. A mola exterior está apoiada na base da caixa e a mola interior apoia-se num segundo diafragma que está exposto de um lado à pressão atmosférica e do outro lado à pressão ou vácuo do colector de admissão. O regulador inclui ainda uma lâmina bimetálica aquecida electricamente apoiada no prato das duas molas.


Fig. 2.36 – Regulador de pressão de comando

O combustível à pressão normal da bomba desviado através de um orifício de estrangulamento
existente no diafragma de aço do dosificador é dirigido por meio de um canal para a parte superior
deste. Ao mesmo tempo a pressão que actua no topo do êmbolo é comunicada também ao regulador de pressão de comando.

FUNCIONAMENTO EM FRIO

Com o motor frio, a lâmina bi-metálica pressiona o prato das molas permitindo a distenção do diafragma do regulador e por consequência o retorno de combustível ao depósito o que se traduz numa redução de pressão de comando. Esta redução de pressão na parte superior de êmbolo implica, para um mesmo volume de ar aspirado, um deslocamento maior do êmbolo do dosificador com o subsequente enriquecimento da relação ar/gasolina.


Fig. 2.37 – Regulador de pressão de comando com o motor
frio

FASE DE AQUECIMENTO
À medida que a lâmina bi-metálica vai aquecendo electricamente, a cavilha sob tensão das molas,
pressiona o diafragma no sentido de bloqueio.
Assim o retorno de combustível ao depósito diminui. A pressão de comando aumenta e com ela a
força contrária exercida sobre a alavanca do disco deflector, empobrecendo a mistura.


Fig. 2.38 – Regulador de pressão de comando com o motor frio


2.2.5.11 – OS INJECTORES


Abrem automaticamente a cerca de 3,3 bar de sobrepressão, não tendo, qualquer função de
doseamento abrindo, simplesmente, quando a pressão chega à pressão referida.
Como já foi dito, os injectores pulverizam o combustível continuamente, penetrando a gasolina
nas câmaras de combustão quando a respectiva válvula de admissão abre.


Fig. 2.39 – O regulador corta o fluxo de combustível fazendo aumentar o valor da pressão de
comando no distribuidor/doseador


Fig. 2.40 – Injector mecânico do sistema K-Jetronic

2.3 – O CIRCUITO ELÉCTRICO

Se o motor pára e a ignição continuar ligada, a bomba eléctrica de combustível desliga-se, por razões de segurança.

O sistema K – Jetronic está equipado com um número de componentes eléctricos, tais como bomba eléctrica, regulador de aquecimento, válvula de ar adicional, injector de arranque a frio, interruptor térmico de tempo. O accionamento destes componentes é comandado por um relé de comando que por sua vez é ligado pelo interruptor de ignição.
Para além das suas funções de comutação o relé de comando possui também uma função de segurança.
Quando se arranca um motor frio, fornece-se tensão ao injector de arranque a frio e ao interruptor térmico de tempo de tempo através do borne 50 do interruptor da ignição.
Se o processo de arranque demorar mais de 8 a 15 segundos, o interruptor térmico de tempo desliga o injector de arranque a frio evitando-se assim que o motor encharque. Neste caso o interruptor térmico de tempo desempenha uma função de temporizador.
Se a temperatura do motor estiver acima dos 35º C, na altura do arranque, o interruptor térmico de tempo já terá aberto a ligação para o injector de arranque a frio que como resultado não injecta combustível.

Neste caso, o interruptor térmico de tempo desempenha a função de interruptor térmico. Por outro lado, o interruptor de ignição de arranque fornece tensão ao relé de comando que liga mal o motor começa a rodar.
A rotação aplicada ao motor através do motor de arranque é suficiente para accionar o relé uma vez que a bobine de ignição, através do terminal fornece impulsos ao relé.
Estes impulsos são processados por um circuito electrónico situado no relé de comando que liga após o primeiro impulso e aplica tensão à bomba de combustível, à válvula de ar adicional e ao regulador de aquecimento. O relé de comando mantém-se ligado enquanto a ignição estiver ligada e o motor estiver em andamento.

Se os impulsos do terminal 1 da bobina de ignição pararem devido ao motor ter parado, por exemplo, em caso de acidente, o relé de comando desliga aproximadamente 1 segundo após a recepção do último impulso.
Este circuito de segurança evita que a bomba de combustível debite combustível quando a ignição
está ligada mas o motor não está em andamento. Arrancando com o motor frio, o injector de arranque a frio e o interruptor térmico de tempo estão ligados.

O motor gira (os impulsos são captados do terminal 1 da bobina de ignição). O relé de comando, a bomba eléctrica de combustível, a válvula de ar adicional e o regulador de aquecimento estão ligados.

O interruptor térmico temporizado comanda a ligação do injector de arranque a frio em função da temperatura do líquido refrigerante.

Partindo de uma temperatura de 20º o injector deve injectar durante 12 segundos.O período de injecção ecresce linearmente até +35ºC. acima desta temperatura, ou depois de ultrapassada uma determinada temperatura durante o processo de arranque, (longo período de arranque), com a consequente abertura dos contactos do interruptor térmico temporizado, a injecção adicional cessa.


Fig. 2.41 – Circuito eléctrico do sistema de injecção K-Jetronic

Sistemas de Injecção Mecânica C.1
Bibliografia
BIBLIOGRAFIA
CASTRO, Miguel – INJECÇÃO A GASOLINA, Plátano Edições Técnicas.
PHILIPPE BROTHIER, Jean – L´injection Eléctronique Tome1 ETAI.
CASTRO VICENTE, Miguel – Transformações em motores de 4 tempos, Edições Cetop – Colecção
AUTOMÒVEIS E MOTORES.
CEPRA – Principio de funcionamento da injecção K – Jetronic.
CEPRA – Plano de verificações para o sistema de injecção de gasolina K- Jetronic.
BOSCH – Automotive Electric/Electronic Systems, 2nd Edition.
DLANETTE, M – Les Moteurs a Injection, ETAI.


Fonte : http://www.google.com.br/search?hl=pt-BR&q=press%C3%A3o+gasolina+dosificador+bosch&btnG=Pesquisar&meta=

Fass ParaBenz excelente post.

Obrigado João... Aguardo complementos dos mestres...

Parabéns Fass... pelo texto original e pela tradução...não lí ele todo aiinda...isso vai ser feito na madruga; sem interrupçoes externas...porem tire uma duvida do asno aqui....
Em quais modelos de MB utilizam esse sistema K jetronic?

Praticamente em todos entre 76 e 86, depois vem o sistema KE. Essa informação não é precisa, talvez haja uma variação de +- 1 ano.

Complementando achamos esses vídeos, são um "curso sobre sistemas K e KE". Não estão em português mas ajudam:
video 1


video 2


video 3


video 4


video 5


video 6


video 7


video 8


video 9


video 10


video 11


video 12


video 13

Excelente post Tio Fass. Tanto original em Ingles como a tradução resumida (e diagramas) me ajudaram a entender como funciona o sistema de injeção mecanica de combustível.

Karl ,excelente!