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Thread: 1990 BMW E30 325i - Trouble Starting after Car sits overnight

  1. #26
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    Seminole, FL, USA
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    1990 BMW 325i Sedan
    Interesting ... I have realoem.com , but I can't seem to find the harness cable, connector or plug for the fuel pump. Since I found one, I'm okay for now. I will look again. Thanks for the information.

    I have a new fuel pump on order and a replacement connector as well.

  2. #27
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    No e30s, again :(
    Cool
    No e30s again.

  3. #28
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    No e30s, again :(
    http://www.realoem.com/bmw/enUS/show...diagId=61_0534

    That is for some. Its under body electrical
    No e30s again.

  4. #29
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    No e30s, again :(
    http://www.realoem.com/bmw/enUS/show...diagId=61_0534

    That is for some. Its under body electrical
    No e30s again.

  5. #30
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    Sep 2015
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    Seminole, FL, USA
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    1990 BMW 325i Sedan
    Thanks for the link. As it turns out, the fuel pump connector is not shown in that list. I looked all through the realoem.com diagrams and could not find a harness, cable or connector that matched. I found that surprising, because I have used the realoem.com to find several other parts and it was always there.

  6. #31
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    No e30s, again :(
    that is weird. maybe bmwfans? http://bmwfans.info/
    No e30s again.

  7. #32
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    Sep 2015
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    1990 BMW 325i Sedan
    I need some help ... Another contributor to this forum sent me messages on the starting issue (via private message). I reviewed the results of my testing to him and relayed that it looked like my fuel pump (faulty check valve) was the problem. He responded strongly that the Fuel Pressure Regulator (FPR) was what controlled the pressure and was the likely culprit. His instructions were to run the engine, then shut it down and disconnect the vacuum line from the manifold and smell for gasoline smell. The instruction continued to say to let the vacuum line hang there and wait 2 hours and smell again. I have done this and so far, I have not smelled gasoline. Another suggestion that came from that conversation was to install a transparent tube to replace the vacuum line between the manifold and the FPR. I did that and ran the car for 5-15 minutes and no fuel showed up in the line (a YouTube video had shown this). I have a new fuel pump ordered that arrives today. If I install it, I may not be able to return it, if it is not the problem.

    One other thing ... Last night I ran the engine and shut it down. I then did the smell test on the FPR and left the vacuum line hanging overnight. I checked it this morning (no gas smell). I then hooked the vacuum line back up and the car started immediately. Can having the vacuum line disconnected from the manifold immediately after shutdown indicate something about the FPR if it is the cause of my first start problems?

    Any and all feedback will be appreciated ...

  8. #33
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    No e30s, again :(
    hmm. I don't know. its interesting that it started fine after sitting unconnected. how much is a new fpr?
    No e30s again.

  9. #34
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    1990 BMW 325i Sedan
    I found an inexpensive FPR on Amazon. I bought it for $24. I couldn't find a lot of info on how good it is, but it is compatible. For the $24 it will allow me to test that the FPR is the issue without unpacking the new fuel pump.

    The other contributor who believes it is the FPR and not the fuel pump sent me this ...

    Yes I still think its the regulator that is f***king this up. On the E34 there is only one hose in the tank that is connected to the fuel pump - the output line. The return line leads back into the tank and not the pump. The only way fuel would drain back into the tank through the output line after shutdown would be if the output fuel hose clamped to the pump was loose, permitting fuel to drain back through gravity. That is far fetched because it if was that loose the high fuel pressure would have pushed the hose off the pump by now and the car wouldn't run under any circumstances.

    His comments seem to indicate he thinks I have an E34 or an E36. I don't ... I have a 1990 E30 325i 4 door sedan. I'm not sure if his fuel system idea is accurate for my model. I need to do some research on that.

    Any thoughts?

  10. #35
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    No e30s, again :(
    i think if its a similar year, e34, it probably a similar fuel system set up.

    but, for 24 bucks, it will work for testing. I think the fuel pump will fix it though. I guess we will see in a few days
    No e30s again.

  11. #36
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    UPDATE ... I ran two tests yesterday and overnight. In each of the tests, I started the car (with normal struggle on first start), let it idle a few minutes to get fuel pressure stable, shutdown the car and clamped (using vice grips) the Source Fuel Line to the Fuel Rail. In the first test I waited 6 hours, in the second I waited overnight. After waiting I then attempted to start the car with the clamp still installed.

    The results of the tests were the same in both cases. With the clamp still installed, I attempted to start the car. I let it crank a while (normally the car will eventually start to fire in less than 10-15 seconds). It would not start (no fire either). I tried a second time in both cases (clamped) with no start or fire. I then released the clamp and in both cases, the car started almost immediately.

    These results seem to indicate that after clamping the Source Fuel Line and waiting, the fuel in the Fuel Rail drains back through the Fuel Pressure Regulator (FPR) into the Return Fuel Line so that there is no Fuel in the Fuel Rail to start the car. Also, since, in both cases, after removing the clamp on the Source Fuel Line the car starts almost immediately, it seems that the Source Fuel Line remains full of fuel because there is little delay to refill the line.

    The FPR seems to be faulty. I believe that when the car is shutdown and the vacuum from the manifold is lost, the FPR is supposed to close to prevent fuel from draining back through the FPR into the Return Fuel Line. Further, the Fuel Pump does not seem to be faulty as the Fuel in the clamped Source Fuel Line did not drain back through the Fuel Pump.

    The new FPR I bought is arriving today (just confirmed in tracking data). Assuming the analysis above is correct, installing the new FPR might solve the start issue, but we will see.

    I'll send an update after testing with the new FPR ...

  12. #37
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    No e30s, again :(
    ok.

    I am keeping up on what you find for our car's fix
    No e30s again.

  13. #38
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    Update ...
    Yesterday afternoon, I received the new Fuel Pressure Regulator (FPR). During the install of the new FPR, I found that the Fuel Line to the FPR was fused to the FPR. I don't know if it was glued or it just got that way over time. As I tried to disconnect it, the last 3/4" of the fuel line torn and I had to cut it off. I used a knife to get the 3/4" remains off and it is so fused to the shaft of the FPR's port that only scraping would remove the remains of the Fuel Line. I'm suspicious that the old FPR is the original one installed during the build of this 1990 E30 325i. Fortunately, there was enough slack that the Fuel Line was still usable with the new FPR.

    After I installed the new FPR, I got the car started, let it idle a minute or so, and then shut it down. I waited 5 1/2 hours and then tried starting and it started right up (no struggle or extended cranking). I let it run for about 1 minute and shut it down. I then let it sit overnight and this morning (after about 11 hours sitting), I tried starting and again it started right up (no struggle, no extended cranking).

    These early tests lean toward the FPR having been the problem. I'll use it as is for a while and provide another update in a few days that will hopefully say my starting problem is solved.

    Looking good so far ...

  14. #39
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    No e30s, again :(
    bad ass that the fix could be that easy. I will swap the fpr on my son's car with mine, since my car starts perfectly
    No e30s again.

  15. #40
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    Hope the switch goes well. Let me know if it works. I wish diagnosing it hadn't been so complex. The exercise was good in that I learned a lot about the fuel system and some on the electrical controls.

  16. #41
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    No e30s, again :(
    i will let you know
    No e30s again.

  17. #42
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    UPDATE 10/29/2018 ...
    I still have the NEW Fuel Pressure Regulator (FPR) in my 1990 BMW E30 325i. For a day or so, it seemed to have fixed the problem, but yesterday on a short errand trip, I noticed some odd behavior.

    After the first start in the morning, I traveled a short distance (< 1 mile) and twice, the engine speed "hiccuped". The engine momentarily reved up, then went back to normal. I never experienced the engine speed "hiccup" with the old FPR. I drove to my destination (5+ miles). Did my errand (30+ minutes) and then came out to start my car, and it struggled to start (not as bad as with the old FPR, but had to crank a while to start).

    I went and got a loaner Fuel Pressure Test kit from Auto Zone and put the gauge on a T in the Source Fuel Line to the Fuel Rail. The Fuel Pressure Readings I got were ...

    Fuel Pressure Time After Start/Shutdown
    33 psi 0
    35+ 15 min
    34+ 20 min
    34 34 min
    24 1 hr 17 min
    16 2 hr 8 min
    10 3 hr 18 min
    8 4 hr 30 min
    6 5 hr 48 min
    6 6 hr 34 min

    I started the car at this point and it started "okay" no excessive crank required.

    I thought that the Fuel Pressure would hold up within maybe 10 psi of the idle pressure. Also, when I did Fuel Pressure Tests with the OLD FPR, the idle pressure was 36+ psi, as opposed to the NEW FPR's 33+.

    What should the Fuel Pressure look like in a normal working system?

    Is it possible that this new FPR is faulty?

    Any thoughts ?

  18. #43
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    No e30s, again :(
    Its possible its bad. I am not home so cannot get the fuel pressure numbers from my book for you.

    And my son has been all over and never swapped the fpr so i am not sure if it helps, yet
    No e30s again.

  19. #44
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    New Update ...
    The car has been starting, but sometimes it takes a few more cranks. I ran a fuel pressure test, and it still drops, but seems to hold at 6 psi. (after waiting overnight) versus the 0 psi readings I had with the old FPR.

    I tried something to see what is happening in the fuel lines. I bought some clear tubing and inline couplers and put about 6 inches of clear connected to the FPR's return line and the source line connection to the fuel rail. After I turned off the engine, both lines were full of fuel. Within 10 minutes, I could see air bubbles starting to show in the return line from the FPR (note that the clear tubes had upward bends before they turned down to the connections with the normal fuel lines, so bubbles would show at the peak of the clear tube bends). After about 1 hour, air bubbles started showing in the source line. From there, in both the return line and the source line, the sizes of the air bubbles in the lines increased. After 9 hours, the return line bubble was about 2 inches long and the source line bubble was 3 1/2 inches long. The next morning, both clear sections of line were empty of fuel. When I started the car, it started after a few cranks.

    Currently, the starting is improved over what I had with the old FPR, but I think things still are not "normal". I'm suspicious that I had two problems ... Bad FPR and Fuel Pump that lets the fuel drain back.

    I haven't decided what to do next. Suggestions?

  20. #45
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    I have 3 325i repair manuals, a Bentley,a Chilton and a Haynes. For residual pressure after the pump is off, the Bentley has nothing, Haynes says should retain pressure for 5 minutes, and Chilton says pressure should be at 38 or above for 20 min.

  21. #46
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    No e30s, again :(
    Man, no idea Here. My son hasnt changed his fpr, still, so i cannot recount what it does for him.

    My 86 325e still starts good with non bmw pump in it. I just changed the actual pump motor with, i think, a taurus or a 76 vega pump motor and its been perfect
    No e30s again.

  22. #47
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    Just FYI ... I believe most older BMW's with the Air Flow Meter (connected to the Air Box) ... the fuel pump won't run, until it senses air flow. Why? ... to avoid flooding, or to prevent the fuel pump from continuing to run in the event of a roll over.

    I know it was this way on my 1976 BMW 530i.

    So I wouldn't expect to hear the fuel pump running with just the ignition on.

    I just purchased a 1988 BMW 325i convertible that had been sitting for a year or two from a broken timing belt. Once I got it back together, it did the same as yours ... wouldn't start after sitting. I suspected loss of fuel pressure at the fuel injectors (probably deposits from sitting). I poured two bottles of Gumout F.I cleaner in the tank. After about a week of driving ... no more problems!

    If one or more of you fuel injectors is leaking ... you'd never see it since it's internal. Although in your case, fuel deposits don't build up over night ... so you may just have one (or more) bad leaking injectors.

    - - - Updated - - -

    By the way, newer VW's have a novel approach to solving this problem. They wire a fuel pump relay into the driver's door electrical contact. When the driver opens the door, the fuel pump runs for a few seconds then stops ... to build up fuel pressure before starting.

    It's a solution that kind of eliminates starting problems from leaking injectors.
    Last edited by Geoffzie; 11-05-2018 at 02:18 PM.

  23. #48
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    No e30s, again :(
    e30s run the pump off the crank sensor reading the engine turning over. if the crank sensor doesn't see the hall sensor picking up the missing tooth, it doesn't send power to the relay for the fuel pump. on etas, its one of the sensors in the trans, on the I models, I think its the one of the front. I cannot remember for sure where its at but I think that's where its at
    No e30s again.

  24. #49
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    Hi guys, i know its an old topic, but i wonder if there was a solution for this problem? Have the same problem that hunts me for a long time now..

  25. #50
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    Quote Originally Posted by Dirk V View Post
    Hi guys, i know its an old topic, but i wonder if there was a solution for this problem? Have the same problem that hunts me for a long time now..

    what have you done chasing remedy ?

    if you go through the thread superj pretty much hits all the right diagnostics. the op probably stopped posting when he hit on a solution. check rail resting pressure at shutdown and once it sat overnight. best way is plumb in a gauge on the line. fpr is a good place to start. pumps etc from there.

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