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  1. #1
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    Please Help! Dead in the water.

    I have a '90 535i. I was coming home last night and all of a sudden I heard a funny noise that I can only describe as a screeching sound, not loud, but noticable. It appeared to be coming from the center or rear of car. I lost all engine power and it died. The engine cranks fine, with no unusual noises. After thinking about it I decided it might be the fuel pump had gone bad.

    I have this morning done the following.

    I pulled the hoses off the fuel pump and turned on the key. No buzzing of the pump motor and no fuel. I then turned the engine over, and fuel pumped out of the delivery side connection. Is this normal? I was expecting the pump to pressurize as soon as the key was turned on. I have checked spark by putting a timing light on and it flashed., so I do not believe it is a spark issue.




  2. #2
    Big Dog
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    Re: Please Help! Dead in the water.

    The fuel pump on the big six is only energized when the engine is rotating. The ECU receives a signal from the crank position sensor that the crank is turning and in turn energizes the fuel pump relay so the pump runs, so yes, this is normal.

    The pumps do sometimes make a loud buzzing or screeching sound, particularly when low on fuel, this is a sign of age and/or wear but I have seen some give a pretty loud hum for quite a while before they fail altogether.

    Since it began suddenly, it's probably a sign the pump is on it's last legs.

  3. #3
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    Re: Please Help! Dead in the water.

    How do I confirm it is the fuel pump that has failed. Don't want to buy one and find out it is something else

  4. #4
    Big Dog
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    Re: Please Help! Dead in the water.

    Some questions:

    1. Does the engine now run and fire up?
    2. When you say gas comes out the delivery side, what is the volume, just a little or a big, pressurized stream?
    3. Does the pump make any noise while pumping with no pressure?

    Having gas come out with no back pressure and having a pump that will deliver the needed volume and pressure are two different things. It may be that the pump has indeed failed and won't give you any pressure when connected to the system. Only sure way to tell is to hook up a fuel pressure gauge to the system and see it you get the right output. I can pull out the Bentley and look it up or maybe someone here remembers it off the top of their head. I'm willing to bet the pump will scream when it's asked to deliver under pressure.

  5. #5
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    Re: Please Help! Dead in the water.

    1. Engine does not start. It turns over as normal, but I get zero ignition.
    2. I had a friend that viewed the fuel volume while I turned the key so I am not sure of the volume. I will check that though and let you know.
    3. I will get back to you on noises.

    I have a Bentley and it says 2 quarts in 30 seconds.

    I really appreciate your help.

    Mark

  6. #6
    bonzo
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    Re: Please Help! Dead in the water.

    I think Big Dog is on the right track. Sounds like the fuel pump. Pinch the "Return line with the pump engaged, if you hear the noise again and the preasure drops- its the pump. You need a minimum of 43 PSI on the test guage to turn run that 3.5 You should have 48-52. Also the lack of preasure in the high preasure fuel rail will make the preasure regulator squeel. Its at the rear of the high preasure rail, close to the bulkhead. Normally the preasure reg will outlast the fuel pump by 100K miles so it should be OK.

    Befor you do a fuel preasure test, make sure your fuel pump "sump" screen (bottom of pump) is clean and clear, and if you have an inline fuel filter- check that to prior to preasure testing. Good Luck

  7. #7
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    Re: Please Help! Dead in the water.

    I just got your message after running the following test.

    Went to auto parts store and they had a fuel pressure tester loaner.

    I was able to connect it directly from the metal outlet on the pump through the gauge, and connect other end to the hose I took off the pump outlet. In other words, inline. I cranked the engine and the gauge quickly rose to about 58psi. When I stopped cranking it dropped to 42psi.

    No unusual noises from pump. No starting at all.
    Nothing but smooth cranking as normal.

    Thanks, Mark

  8. #8
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    Re: Please Help! Dead in the water.

    Just checked the return line and have lots of flow coming back to the tank when cranking.

  9. #9
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    Re: Please Help! Dead in the water.

    Cranked engine over about a dozen times and checked tail pipe.
    Can smell raw gas from exhaust.
    Hooked timing light to plug 1 and cranked it over.
    I got flash from gun so I guess I probably have spark.

    What the heck is goin on? I am at a loss!

  10. #10
    Big Dog
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    Re: Please Help! Dead in the water.

    Well let's review:

    The three things needed to make an internal combustion engine run are:
    The proper fuel/air mixture
    Adequate compression
    A properly timed spark

    The compression here is a given, leaving the other two.

    Since you've checked the fuel pressure, we have to assume the fuel is there, leaving the spark as the problem. Just putting a timing light on and checking for voltage at the wire is normally the way to go, in this case, try pulling a plug and making sure it's firing. It could be that you've cranked it over so much the plugs are now fuel fouled and won't fire correctly.

  11. #11
    bonzo
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    Re: Please Help! Dead in the water.

    If you have enough fuel/preasure and you are SURE you have a good spark, you may want to look at your crank position sensor. You probably won't get a code with the DME 3.1 so you will have to test the Ohms to be sure. If I remember correctly the Bently has conflicting specs on the 535i for the CPS. Big Dog might be able to shed some light on the numbers for you. Usually the CPS will slowly go south, but they can a up all at once too.

  12. #12
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    Re: Please Help! Dead in the water.

    Would it still fire the the fuel pump if it was bad. Isn't that the sensor that makes the pump activate?

  13. #13
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    Still no resolution.

    Could this be an issue with a jumped timing chain? Based on the fact that I seem to have fuel and spark, I am wondering if maybe the timing is just out of whack. This is driving me nuts and I am trying to avoid taking it to the shop and getting ripped.

    I do appreciate all your help.

    Thanks, Mark

  14. #14
    Big Dog
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    Re read my previous post

    You may have fuel fouled the plugs and they aren't firing correctly.

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    Re: Re read my previous post

    I pulled 3 of the plugs out to check how they were burning and spark. All 3 looked to be burning clean, had good spark, and did not appear to be fuel fouled.

  16. #16
    Big Dog
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    Well then you really do have a mystery....

    Okay, spark, assume compression (use a tester or just have someone crank it over and feel at the plug hole) so we're back to fuel. Just because you smell gas at the tailpipe doesn't necessarily mean it's being delivered at the right time, in the right amount or is properly atomized. Since this entire problem begain with what we assume is a fuel pump problem, that's the place to go. I have an extra 535i pump that was take out because it was getting old but it's a known good part. Where are you? If close you can pick it up, or just pay for the shipping and you can have it.

  17. #17
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    Re: Well then you really do have a mystery....

    The only thing I have not confirmed is compression. Have just assumed it had that. I will pull plugs and check that today.

    I live in Calif. on the coast so you would probably need to ship it to me. I would gladly pay the shipping and even return it to you after testing it out, just in case you would need it for something else in the future.

    Thanks, Mark

  18. #18
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    Major Development


    Ok, Finally something to get my teeth into. Probably not good news.

    Just ran compression test on 1st 3 cylinders and all 3 are between 50 and 55 psi. Didn't think I needed to run the rest tonight.

    So based on all we know now.
    Driving smooth down the road, screeching sound, and instant power loss.

    I don't know alot about this kind of issue. So I am asking.
    What happened? Jumped timing chain? failed tensioner?

    Is this a interference motor. Is it worth fixing?

    Thanks Big Dog and bonzo for all your help.

    Mark


  19. #19
    Big Dog
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    Re: Well then you really do have a mystery....

    Mark,

    e-mail me directly with your shipping address and I'll send it to you, just make a donation to BMW Foundation for Street Survival.

    Big Dog

  20. #20
    GadgetNutt
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    Re: Well then you really do have a mystery....

    Bummer! See my post at top. "Major Development"

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