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2.5 v6 TDI 180hp injection timing problem

Discussion in 'A6/S6/Allroad forum (C5 Chassis)' started by blackwagon, Oct 28, 2009.

  1. blackwagon
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    blackwagon Member

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    [Oct 28, 2009]
    Hello,

    I just monitored the injection timing of my 2.5 V6 TDI engine (AKE)
    When I look in measurement block 4 of the engine ECU (using the 5052) I see engine rpm in field 1, an injection angle which changes with rpm and load (from 2° atdc to 12°btdc) in field 2, field 3 stays fixed at 0.0 btdc, field 4 shows a percentage which varies with load and rpm.

    Am I correct in assuming field 2 shows the requested injection timing and field 3 the actual injection timing ? If this is te case there is something wrong.
    I now my needle lift sensor is faulty, it gives an error code in the ECU (shorted to +, permanent error, I can't erase it). Could this be the cause ?

    Best regards

    Stefan
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  2. adamss24
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    adamss24 Well-Known Member

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    [Oct 28, 2009]
    The pintle needle injector is telling the ECU how much to advance or retard the timing. The car is relying on the needle injector to calculate the sweet spot and as such, it will run to a pre-learned value (if the 3rd injector fails) albeit at reduced power and increased fuel consumption. Replace that injector first then worry about timing after...
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  3. blackwagon
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    blackwagon Member

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    [Oct 28, 2009]
    Hello,

    I will replace the injector with the needle lift sensor next week, I already suspected that it would have an impact on the fuel mileage and performance but then again I read that the VP44 doesn't actually need the needle lift sensor (Opels with VP44 wouldn't even have the sensor I was told) On the other hand I find it questionnable that Audi would install costly sensors for no reason.

    My fuel mileage is rather poor, about 25mpg and that is driving verrry easy (shifting at 2200rpm, accelerating gently, highway miles never exceeding 80mph, cruise control)

    I already cleaned the MAF, that brought me 1litre/100km instantly !

    The injection timing in Measuring block 4 still puzzles me, field 3 constantly stays 0.0 , while the percentage in field 4 varies nicely around 40% (never reaching more than 90% or less than 5%). Could it be that it tries to adjust the injection timing but the actuator in the pump is stuck ? Then again, if the needle lift sensor is constantly shorted how can the ECU know where to adjust to as it doesn't know the actual injection point that is present ? :shrug:

    It's a 6 speed manual quattro

    B.R

    Stefan
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  4. adamss24
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    adamss24 Well-Known Member

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    [Oct 28, 2009]
    This single piston pump operates at a higher pressure - up to 1400bar (20,500psi), has its own built-in PSG5 ecu & communicates with the main ecu via the can bus (Controller Area Network). The pump ecu needs only to be told how much fuel to inject. It does all the rest, calculating the start & end of the injection and compensating for fuel temperature etc. The 6 hole injectors operate with a two stage injection to reduce noise and improve emissions.
    Unlike the VP37 pump, in this pump, the injected quantity is varied by altering the duration that fuel is supplied. A high speed solenoid valve releases the pressure and as soon as this drops below the injector opening pressure, the injection is terminated. A rotating disc distributes the fuel to each injector in turn. This pump is also rated at 25kw / cylinder. The maf sensor plays an important role in controlling the fuel quantity injected. So like many VAG (& other) models with EDC15m, are very sensitive to out of spec mafs.
    NEEDLE LIFT SENSOR
    This is built in to no.1 injector and indicates to the ecu exactly when injection has commenced by providing a pulse when the injector opens. If it is missing due to a fault or short circuit, the engine runs unevenly and may be down on power. If the needle lift sensor is faulty the ECU will use the CKP - CRANKSHAFT POSITION SENSOR. Tells the ecu when TDC is reached, measures the crank angle and also is used to provide the engine rpm.
    Last edited: Oct 28, 2009
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