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    Fuel problem?

    So, my BMW (1987 325is) is having pulsing acceleration and stalling problems. The problems began while driving up to school. After driving for a little over 100 miles the engine started pulsing during acceleration. At first it was hardly noticeable, but then it got worse and worse to the point where it completely stalled and left me stranded on the side of the highway. At that point the engine would start after some cranking but only idle for 30 to 55 seconds, after which it would stall. Even while giving it extra fuel. After i got it towed home, i got it to run again after replacing my main, fuel pump and o2 sensor heater/purge valve relays, My ignition coil, and both of my coolant tempter sensors. I cleaned out my mass airflow sensor and my idle control sensor. And i replaced all of the vacuum lines. There may be some vacuum leaks elsewhere but it doesn’t seem to be a vacuum issue specifically. I have replaced the fuel filter roughly 9 months ago. The oil cooler was smashed by the tow truck and my radiator support was a little damaged, The cooler has since been replaced.

    After i got my car to run, I drove it and it will drive for about 2-8 minutes before stalling out, during which time pulsing during acceleration still exists and would progressively get worse.


    Today i decided to test the fuel pressure. So i de-pressurized the system and put the gauge right before the pressure regulator. However when i detached the line going to the regulator, the line was dry. Which seemed odd. When i tried to start the car, it ran for 30 seconds again and died. The fuel pressure read zero the whole time. After cranking again for a while the engine will not start, and still no pressure.

    I tried jumping the pins on the relay to see if the pump would pump anything but it didn't. i tried to listen to the pump to see if it wasn't buzzing and it wasn't.

    Does this confirm that the pump is the suspect? Why would the car run and drive for a little while and then after de-presurizing the system would it not even start?
    -Paul

    #2
    When you jumped the relay pins did you turn the engine over ? If you didn't then no power will get to the fuel pump because the DME can't see the engine turning signal from the CPS and won't power the fuel pump fuse (11).

    So..

    If you fire some easy start into the intake does the car start ?
    - confirming a fuel problem.

    Are you seeing 12v on fuse 11 when cranking the engine ?
    - confirming fuel pump power feed is in order.

    What voltage are you getting at the pump when cranking ?
    - confirming that power is getting to fuel pump plug.

    When you installed the new fuel pump, was this an OEM unit or a Walbro type replacement ?
    - The pump power plug on these can disconnect if it isn't pushed fully home until it clicks.

    When pressure testing, connect up at the fuel rail feed. Make sure you aren't testing the return line. My E30 feed connects to the right rear of the fuel rail.

    Start your pressure test at the fuel rail feed (right rear of the fuel rail)
    - Use a dead end connector into the fuel feed hose.
    - You should see 70 - 80 psi, the circuit should hold this pressure. Relieve the circuit pressure after a couple of minutes.

    Any fuel in the fuel regulator vacuum line or outlet ?
    - New fuel pump can blow an ailing regulator (ask me how I know this)
    - T into the fuel feed at the rear of the rail, you should see 40 psi (ish). Again the circuit should hold that fuel pressure.

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