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1984 318i No Start

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    1984 318i No Start

    Hey everyone, recently my fuel pump relay went out while driving, and my car died in the middle of the road. Once I got a new fuel pump relay and installed it, the car will not start anymore and I'm not sure if there is another problem that caused the fuel pump relay to go out. Once I replaced the fuel pump relay the fuel pump primes again and the engine tries to start but it sounds like it has a really bad misfire and will not start at all. There is also a strong smell of fuel and I can see faint smoke/fumes coming from the engine but cannot pinpoint where exactly the smoke is coming from. A few other things to note about the engine:
    When I crank the engine and hold the gas pedal down the engine will stay running but run very roughly and when I let go of the gas it dies immediately
    There is spark and the spark plugs and wires were replaced a few months ago
    If I flood the engine and pull the fuel pump relay out the car will start and run smoothly until there's no more fuel in the engine (a few seconds)
    I did a compression test as well recently and the compression was fine
    I cannot see any major vacuum leaks but I haven't done a smoke test so I can't rule it out. I'm also not sure if it is a vacuum leak as my car was running fine until the fuel pump relay went out
    I tested the cold start valve and it looks like it is working fine

    I haven't tested the injectors and fuel pressure yet so I'm guessing it might be something to do with the injectors, fuel pumps, or fuel pressure regulator but I'm completely lost as to why it stopped running all of a sudden and has a really bad misfire now that I replaced the relay. Any help is appreciated! Thanks!

    #2
    First, is the fuel pump fuse good? You say the pump primes but I thought the M10 cars did not fire the pumps until the crank was spinning/ignition was firing (It's been a while so I could be wrong here). I think this is fuse 11 - 15 Amp.

    You can jump pins 87 and 30 of the fuel pump relay (with a fused wire) to run the pumps without the car running (but key "on") to verify operation of the pumps (there are two: in tank and under car) and also do a fuel pressure and delivery test. If the car seems to be flooding and you have spark, I would verify pressure first. If the fuel side seems good, then I would move on to vacuum leaks, etc.

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      #3
      I tried jumping the pins and I can hear the inline pump running I’m not sure if I can hear the in tank one running though. The fuses look good and I’ll try to get a fuel pressure tester and test the pressure sometime today.

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