Megane 1.5Dci Injection Fault

[AlexB]

Hi DarekW,

The diagrams look fine. In the first file one can see the response of the ramp pressure being slightly delayed with respect to the demand, which is close to normal. In the second file I see the ramp pressure being unable to reach the demand by a small value at the full throttle. You wrote that the fault occurs when accelerating, so the full throttle mode might be more relevant.

In these engines the injectors are coded into the ECU. I think that due to wear the injectors have changed their characteristics, but their original codes are still in the ECU. It is also possible that they were swapped between the cylinders without re-programming the ECU. This may cause "capping" the ramp pressure around its maximum and/or minimum values.

Apart from the above problem, I see the MAF value being constant under variable revs. It is strange...

[DarekW]

Hi AlexB,

Thank you for your fast reply. I also think that this difference is because when throttle is being open for milliseconds it will take another milliseconds to inject the fuel, burn it what will cause RPM rising ...and it will speed up the pump so it will generate bigger pressure I'm just not sure if this delay must be so "big". Injectors were repaired but without replacing the nozzles so every technician here in PL says that there's no need to generate new codes and second thing that this engine model has got a knock sensor which helps the engine to adapt even the nozzle replaced injectors. For sure they were not coded with new codes, and not generated any. I've checked the injectors and they are in "proper" places, code on each injector correspond with proper code in ECU. But that's another clue. I was also wondering if there's no need to generate new codes. Next monday I should get info from another service so maybe the injectors correction values will show that there's problem with injectors... Right now I feel stupid, I read many forums and still in same position that I have no clue what causes my problem.

[AlexB]

Hi DarekW,

I don't think the knock sensor is of help here, because it has nothing to do with the return flow from the injectors. If the return flow is too high, then the ramp pressure can't keep up with the demand, thus causing the fault. The return flow can be measured, but it is measured at the revs different from the conditions when the fault occurs...

Other options include the pump, obstructions in the fuel line, fuel temperature sensor... Check MAF as well, as it may cause surges of pretty much all parameters in the transitional modes.

[DarekW]

I was informed that my engine type adapts the injectors using the knock sensor and by the way if that would be the cause of my problems then fault message should show up repeatedly in same conditions but month after month it shows up more often..that's why I think that another thing is a problem but of course I'll tell technicians to check injectors correction values etc. What I checked, all other values including temperatures, fuel flow rates are ok (confirmed on PL forums with other cars values) and also I was told that K9K 722 engine doesn't have a MAF sensor so it shows constant value all the time in diagnostic software.

[Logic28]

Does not matter what car, if the rail fuel pressure isn’t correct it can be one of the following:

1) Pressure regulator/return flow faulty
2) High pressure stage fuel pump lazy
3) Leaking injector/s letting fuel escape into the return line

[DarekW]

Thanks.
Maybe you can tell me if the pressure on the graphs is ok?