E46 Fuel Pressure on B3s

Discussion in '3 Series' started by DogWagen, Jul 29, 2020.

  1. DogWagen


    May 17, 2020
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    +2 / 0 / -0
    Hi All,

    I'm the process of sorting out a long-standing Fuel Trim Fault code on my Alpina B3s and would appreciate a bit of advice regarding fuel pressure (for reference, Pump is standard E46, engine-mounted regulator is from an E36 M3).

    Tested the fuel pressure. 3.1-3.2 Bar before start and 2.9-3.0 bar while running. After 20 mins, from switch on-switch off, pressure drops by 0.2 Bar. When I clamp off the return line from the regulator, the pressure spikes to 3.5 Bar and then rapidly decays to 3.1 bar.

    Given that the Alpina uses the standard E46 fuel pump, I'd expect 3.5 bar or 51 PSI at switch on versus the 3.1 ish I'm seeing. The fact that it doesn't change when the return line is clamped would indicate to me that that the fuel pump is the likely candidate.

    Is there anything else I could have overlooked or suggestions before spending out on a replacement pump (£300-odd for OE or about £100 for a Pierburg which I think is likely to have been OE) .

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