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Thread: 000135 rail pressure code

  1. #1
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    000135 rail pressure code

    We have a 2008 audi Q7 3.6 with a 000135 fuel rail pressure issue. Low pressure system tests fine and holds the roughly 6 bar it should with a pump that stays at the 50 percent it should and passes a volume delivery test. The rail pressure is 35 bar at idle and slowly falls to low system pressure when under load with all cylinders misfiring as you'd expect. If the car is driven without applying accelerator too hard can be driven up to 80mph with no major issues, police being excepted. The high pressure pump was replaced with no change. after many tests i am wondering if anyone has replaced a fuel manifold as there seems to be a mechanical bypass built in. The car currently has 200,000 mi
    Last edited by Swedish Imports; 03-10-2020 at 03:15 PM.

  2. #2
    Ross-Tech Employee DrPeter's Avatar
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    Hello,

    Personally, I have not seen a "fuel manifold" fail on a BLV-3.6l engine. I have seen the brass "pressure limiting valve" [03C 103 363 H] fail and cause fuel rail pressure concerns. That part number is the newest supersession, which tells me these may have had issues in the past.

    Just in case you have not seen it, we have a Ross-Tech wiki page for the fault code in question: P0087/000135 - Fuel Rail/System Pressure: Too Low

    The rail pressure is 35 bar at idle and slowly falls to low system pressure when under load with all cylinders misfiring as you'd expect.
    - One would expect that the High Fuel Pressure on the Fuel Rail would "Increase", not "Decrease", .

    - If the Fuel Supply System is not able to keep up with the demand for fuel pressure, the pressure would drop and the P0087 fault code could set, so that would be expected.

    I would suggest to have a look at the Measuring Value Block(MVB) group [231] to watch the "Rail Pressure".
    MVB-231, field (2) = Rail Pressure (specified)
    MVB-231, field (3) = Rail Pressure (actual)

    Both of these reading must be within (+/-) 5Bar during the normal operation of the engine. At any time there is more or less than the specified, the ECM can set fault codes.

    If the "pressure limiting valve", the HPFP and the engine are also okay (mechanically speaking, no cam or timing chain issues), then it will be necessary to evaluate the Power and ground of the N276/N290 - Fuel Metering Control Valve on the HPFP.

    The N276/N290 must have battery voltage at all times, the ground signal from the ECM is a PWM signal and must be clean, if the signal is weak or saw tooth like, the ECM could be the concern.

    Do not for get the Official Factory Repair Information

    Hope this helps,

    drpeter

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