Results 1 to 19 of 19

Thread: 325e Fuel pressure

  1. #1
    Join Date
    May 2010
    Location
    Winston-Salem, NC
    Posts
    63
    My Cars
    1987 BMW 325e

    325e Fuel pressure

    For several months now my engine suddenly shuts off while running. I am able to turn it back on. This happens both while driving and when the car is stopped. This happens to me quite often but not always (sometimes I'll be able to run an errand without a problem).

    Recently, as a matter of routine maintenance, I've changed the fuel filter, spark plugs, ignition wires, distributor, and rotor. Recently I replaced the main relay since it is inexpensive, easy to replace, and was mentioned on several posts as a possible cause for the problem.

    Today I did a fuel pressure test. I connected the pressure gauge like this:

    Gauge.jpg

    First I took out the fuel pump relay and bridged the connection with a wire.
    • Without running the engine I get 36psi. However, as soon as I remove the jumper wire the pressure drops rather quickly. Check out this video:

      .
    • While the engine is running, the pressure drops to about 28 psi. After the engine is shut off the pressure goes back up to 36 (jumper wire still there). You can see that in the second video:

      .
    • Then I test the pressure with the relay in place. The pressure is zero until I start the engine. It stays between 26-30psi as I rev the engine. After shutting off the engine the pressure drops rather quickly. You can see this in this third video:



    According to the Bentley manual, 36psi is the pressure specification for eta engines. Is it a problem if the pressure is at most 30 while the engine is running, or is it normal for the pressure to drop while the engine is running? I've read elsewhere that pressure should be maintained after the engine is shutoff but apparently it is not.

    Also, I noticed the fuel hoses were old and cracked. Obviously I should replace them, but could the problem be just that or do I still have a problem elsewhere for sure?

    I did not have time today to test the transfer pump or the main pump. I hope to do that soon, but I thought I would post these results here now and ask about your thoughts.
    Last edited by marsgorski; 03-09-2019 at 07:17 PM.

  2. #2
    Join Date
    Dec 2005
    Location
    corpus christi, texas
    Posts
    5,353
    My Cars
    only the kids e30s
    The pressure should not drop that quick when you shut it off. That makes a long crank to start.

    If it says 36, it should be 36 while running but the sudden dying is from something else
    no e30s of my own, but I am financing two for my kids

  3. #3
    richardodn's Avatar
    richardodn is offline Old Guy BMW CCA Member
    Moderator
    Join Date
    Nov 2008
    Location
    Lakewood, CO
    Posts
    9,314
    My Cars
    '12 X3 35iX, '98 328ic
    The engine off test reading of 36 psi is spot on.
    The rapid pressure drop after pump shut off indicates a problem with the check valve in the fuel pump. You can replace the fuel pump or add a check valve to the supply line. There is a BMW part for that. Hopefully it's not discontinued. In any event that would only cause starting and not running issues. Rapid pressure drop could also be caused by fuel leaking past the FRP diaphragm, through the vacuum line and into the manifold. Have you checked that?
    The engine running and I assume vacuum line connected reading of 28 psi seems a bit low. I would expect it to go no lower than about 33 psi.
    You did not post a result of engine running and vacuum line disconnected. Pressure should rise when disconnected but still remain in that 36 +/- 3 psi range.

    It does sound like you have a faulty FPR, but that is not likely the cause of your car dying. When the car dies, does the tach go to 0 immediately or does it drop slower as the engine rpms drop. If it goes to 0 immediately, it's an ignition problem and I would guess it's one or both of your timing data sensors on the bellhousing.
    Last edited by richardodn; 03-10-2019 at 09:05 AM.
    "Howdy, Folks!"

    1986 Delphin 528e - Has led a hard life, 290k and still alive.
    1989 Zinnoberrot 325iX Sedan - My winter snowmobile. (Deceased)
    1998 Avus Blau 328iC - My topless summer girl.
    1999 Audi A4 Avant Quattro - Crap can, but I'm in too deep.
    2012 X3 xDrive35i - My new snowmobile.

  4. #4
    Join Date
    May 2010
    Location
    Winston-Salem, NC
    Posts
    63
    My Cars
    1987 BMW 325e
    Quote Originally Posted by richardodn View Post
    The rapid pressure drop after pump shut off indicates a problem with the check valve in the fuel pump. You can replace the fuel pump or add a check valve to the supply line. There is a BMW part for that. Hopefully it's not discontinued.
    Looks like it might be this part? If I understand correctly this part is not in the original design of the car but can be added to it, correct?

    https://www.eeuroparts.com/Parts/711...e-11631707770/

    Quote Originally Posted by richardodn View Post
    Rapid pressure drop could also be caused by fuel leaking past the FRP diaphragm, through the vacuum line and into the manifold. Have you checked that?
    I only disconnected the vacuum line before connecting the pressure gauge. I took a look and did not notice any fuel in there, just a slight fuel odor.

    Quote Originally Posted by richardodn View Post
    The engine running and I assume vacuum line connected reading of 28 psi seems a bit low. I would expect it to go no lower than about 33 psi.
    You did not post a result of engine running and vacuum line disconnected. Pressure should rise when disconnected but still remain in that 36 +/- 3 psi range.
    I will test that today and get back with the results.

    Quote Originally Posted by richardodn View Post
    When the car dies, does the tach go to 0 immediately or does it drop slower as the engine rpms drop. If it goes to 0 immediately, it's an ignition problem and I would guess it's one or both of your timing data sensors on the bellhousing.
    Unfortunately my tach does not work, so I cannot tell.

    Quote Originally Posted by superj View Post
    If it says 36, it should be 36 while running but the sudden dying is from something else
    Quote Originally Posted by richardodn View Post
    It does sound like you have a faulty FPR, but that is not likely the cause of your car dying.
    So it sounds like I need new hoses, new FPR, and a check valve. But as you and superj mentioned, none of this is likely to fix the sudden dying. Any ideas on what the problem there could be?

  5. #5
    Join Date
    May 2010
    Location
    Winston-Salem, NC
    Posts
    63
    My Cars
    1987 BMW 325e

    Update about FPR

    So today I did the pressure test again and this time I removed the vacuum hose that goes between the FPR and the manifold.

    Pressure was about 30psi with the engine running. Then jumped to about 37 PSI when I removed the hose. Dropped back down to 30 when replacing the hose:



    I guess that means the FPR is working and there's no point in replacing it.

    Another thing I noticed is that the intake boot has a big crack. I will replace that, but I highly doubt this will fix my main problem.

    Another interesting thing I noticed is there is this wire coming down from the 20(?)-pin connector (I believe this is for computer diagnostics?) At the other end of the wire there seems to be a sensor that's not connected to anything. What is this wire supposed to do and where should it go? I didn't see anywhere obvious where the sensor should go. Any ideas?

    IMG_5565.jpg

    IMG_5566.jpg

  6. #6
    richardodn's Avatar
    richardodn is offline Old Guy BMW CCA Member
    Moderator
    Join Date
    Nov 2008
    Location
    Lakewood, CO
    Posts
    9,314
    My Cars
    '12 X3 35iX, '98 328ic
    Start with the cracked intake boot before you mess with anything else. That's has a big effect on your engine driveability and may fix your main problem. The connector looks like the same one used for ABS and the brake lining sensor but it's in the wrong place for that. If it is connected to the diagnostic connector, it's not necessary. You might be able to figure out it's purpose by determining the pin it's connected to and looking that up on the connector pinout.
    "Howdy, Folks!"

    1986 Delphin 528e - Has led a hard life, 290k and still alive.
    1989 Zinnoberrot 325iX Sedan - My winter snowmobile. (Deceased)
    1998 Avus Blau 328iC - My topless summer girl.
    1999 Audi A4 Avant Quattro - Crap can, but I'm in too deep.
    2012 X3 xDrive35i - My new snowmobile.

  7. #7
    Join Date
    May 2010
    Location
    Winston-Salem, NC
    Posts
    63
    My Cars
    1987 BMW 325e
    Quote Originally Posted by richardodn View Post
    Start with the cracked intake boot before you mess with anything else. That's has a big effect on your engine driveability and may fix your main problem. The connector looks like the same one used for ABS and the brake lining sensor but it's in the wrong place for that. If it is connected to the diagnostic connector, it's not necessary. You might be able to figure out it's purpose by determining the pin it's connected to and looking that up on the connector pinout.
    The intake boot is on its way and should be here next week. In the meantime I tried testing pressure at the transfer pump (the smaller of the two, inside the fuel tank) and also checking voltage and current. I was following the Bentley manual for this (section 6.4.2). I got some very surprising results that I'm not sure how to interpret. There's a video of the pressure test at the end.

    1. I disconnected the output hose and plugged it with a screw. During the pressure test, when I turned on the pump using a jumper wire, a bit of fuel began to leak but not from the end of the hose that I plugged, but from the opposite end that connects to a metal line. As soon as I noticed I stopped the pump as quickly as I could get to the jumper wire.
    2. The most revealing observation was that the gauge did not move one bit. 0 PSI. This makes me strongly suspect that the transfer pump is at fault here. On the other hand would the car start and run (most of the time) if the transfer pump gives zero pressure? The Bentley manual does say "A failure of the transfer pump will not necessarily prevent the engine from running, but may cause starting problems or fuel starvation at the main pump, particularly in summer weather". But could this be true even with zero pressure? Is the main pump able to draw fuel from the tank on its own?
    3. After this test I reconnected the hose. Fuel stopped leaking.
    4. I then measured the voltage across the harness connector terminals. I got a reading of 11.8V, a little lower that what I read measuring directly across the battery terminals (12.4V).
    5. Then I attempted to measure the current. I operated the pump in the same way as before, but before I could get a reading the pump(s) stopped. I looked around and Fuse 11 was blown. I replaced it, and I was able to operate the pumps again. This time I was able to get a reading, except the reading was 0 amps. I don't have much experience with multimeters but I do know the basics and I think I did the measurement according to the manual: I connected a wire from one terminal in the connector to its corresponding terminal in the pump. Then placed the two probes from the ammeter in the other two terminals. I tried other scales of current measurement settings in the ammeter but I always got a reading of zero amps.



  8. #8
    Join Date
    May 2010
    Location
    Winston-Salem, NC
    Posts
    63
    My Cars
    1987 BMW 325e
    Looking at some pictures of the transfer pump I now realize that I connected the pressure gauge to the return line, not the output line. In my defense the diagrams in the Bentley manual are kinda misleading. I will have to check the pressure again, probably next weekend.
    Last edited by marsgorski; 03-17-2019 at 06:20 PM.

  9. #9
    Join Date
    Mar 2010
    Location
    Abilene, TX
    Posts
    149
    My Cars
    1987 325e
    Great diagnostics in your post! Its good to see someone really put in the effort and show how they are troubleshooting.

    In reference to your issue, when the car dies, does it sputter then or or does it just die? If it just dies, in my opinion, this would me an ignition issue. Maybe an ignition control module (not sure of the e30 has one, still learning)?

  10. #10
    Join Date
    May 2010
    Location
    Winston-Salem, NC
    Posts
    63
    My Cars
    1987 BMW 325e
    Quote Originally Posted by jbontke View Post
    Great diagnostics in your post! Its good to see someone really put in the effort and show how they are troubleshooting.
    Thanks! I've benefited a lot from this forum in the past, so I'm trying to be as detailed as possible in case it's useful to others.

    Quote Originally Posted by jbontke View Post
    In reference to your issue, when the car dies, does it sputter then or or does it just die? If it just dies, in my opinion, this would me an ignition issue. Maybe an ignition control module (not sure of the e30 has one, still learning)?
    It seems to die suddenly. Sometimes not so suddenly depending on the gear, rpm, and throttle. But in any case, the engine doesn't sputter.

  11. #11
    Join Date
    May 2010
    Location
    Winston-Salem, NC
    Posts
    63
    My Cars
    1987 BMW 325e

    Transfer pump diagnostic

    Transfer pump:

    Today I finally did the pressure test on the transfer pump correctly. I got zero pressure. The first time I ran the pump I did notice the pressure gauge hose straightening out a bit, as if fuel pressure were building up inside. But the needle didn't move.

    Following the Bentley manual I went ahead and tested current and voltage at the connector on the fuel pump. Here's the interesting thing: I got zero voltage across the wire connector and zero amps from the wire connector to the pump connector. I wondered whether my multimeter was working or if I had it on the wrong settings, but I checked voltage and current at the fuel pump relay connector and there I got readings withing spec (assuming that the readings at the relay and at the connector going into the pump should be the same: 1.4A and 12-13V). So I think I trust my ammeter. When running the pump(s) using the jumper wire I do hear whirring sounds coming from both the main pump (by the fuel filter) and the transfer pump.

    So I'm confused. If there is a whirring sound I interpret that as there being current going to the pump. But the ammeter says otherwise.

    In any case, there's strong evidence now that the transfer pump is not doing its job. My question is: Is it the pump itself, or is it the electrical supply not getting to the pump? Can I remove the pump and do some kind of test on it? I would really hate to throw in an expensive pump while the problem is entirely with the electrical supply.

    Intake Boot:

    I finally installed the new intake boot. The problem almost disappeared. The engine definitely shuts off less frequently now, but it still happens about every other day or so. After installing the new boot I also get some irregular idling sometimes which is an annoying problem I've had before. I checked the intake book and it seems to be installed correctly and not letting any air inside.

  12. #12
    Join Date
    Dec 2005
    Location
    corpus christi, texas
    Posts
    5,353
    My Cars
    only the kids e30s
    You can pull the pumo and clean it with carb cleaner to get it back until you get a new one.
    no e30s of my own, but I am financing two for my kids

  13. #13
    Join Date
    Mar 2010
    Location
    Abilene, TX
    Posts
    149
    My Cars
    1987 325e
    Since the engine just dies, I don't think it would be a fuel issue. From your pressure tests, you have a solid fuel system. I you feel like a new, cheap lift pump, try the vega pump: https://www.r3vlimited.com/board/sho...d.php?t=215034

    One place to rule out is the ignition lock cylinder. Try jiggling the key in the lock while the car is running. If it dies, then that could be the reason for an intermittent engine stall.

  14. #14
    Join Date
    May 2014
    Location
    Central NJ
    Posts
    23
    My Cars
    85325e,97318i,87vlv240
    thats a sensor, that goes on top-right (if you're looking at the motor from the front) by the harmonic balancer there should be a holder for it right above your crankshaft on the timing belt cover.
    Last edited by shawnkhanobi; 04-06-2019 at 10:20 PM.

  15. #15
    Join Date
    May 2010
    Location
    Winston-Salem, NC
    Posts
    63
    My Cars
    1987 BMW 325e
    Quote Originally Posted by shawnkhanobi View Post
    thats a sensor, that goes on top-right (if you're looking at the motor from the front) by the harmonic balancer there should be a holder for it right above your crankshaft on the timing belt cover.
    Thanks, I'll check it out when I get home. Do you know what that sensor does? More specifically, could it be causing the engine to shut off while driving?

  16. #16
    Join Date
    May 2014
    Location
    Central NJ
    Posts
    23
    My Cars
    85325e,97318i,87vlv240
    not sure what it does, but i know the car doesn't care about it. it might be for diagnostic purposes. i was also very curious when i discovered it so i ran the the with the sensor in place and out of place to see if it made a difference. it didn't make any difference.

  17. #17
    Join Date
    Dec 2005
    Location
    corpus christi, texas
    Posts
    5,353
    My Cars
    only the kids e30s
    i think its diagnostic also. it never effected my cars, either
    no e30s of my own, but I am financing two for my kids

  18. #18
    Join Date
    Mar 2010
    Location
    Abilene, TX
    Posts
    149
    My Cars
    1987 325e
    marsgorski, any progress on the issue?

  19. #19
    Join Date
    May 2010
    Location
    Officially in Tampa
    Posts
    2,118
    My Cars
    87 Cabrio & 87 ETA
    On an eta the sensor on the balancer does nothing. I had a similar sudden death symptom on my cabrio that went on for ages.it would start when cold and run til it reached OT. At first it would die then restart. As it progressed, it would die then have to sit before it would restart. Always fine cold, never fine at OT. Long story short, I finally check the fuel pressure and it was fine til OT then went to zero. New high pressure pump and problem solved.

    if you hear a loud sucking sound by your rear tire it means your transfer pump is dead and the HP pump is pulling which it's not designed to do. What you hear is cavitation.

    Intake leaks first and if you replace the reference sensors (not a bad idea) do both and try not to cross them as they are identical.
    87 Zinno Cabrio 98k Barn Find. Build thread http://www.r3vlimited.com/board/showthread.php?t=268987
    87 Lachsilber ETA Time Capsule. bought w 125k from 87yo original owner

    Cabrio deck lid & hinge struts (w sleeves) now for sale. See the link below for more info

    New "made in Europe" seat shocks. PM for details
    http://www.bimmerforums.com/forum/sh...ot-Seat-Shocks

Similar Threads

  1. FS: Throttle Assembly and Fuel Pressure Regulator 325e/325es
    By 89vert507 in forum E30 Parts Classifieds
    Replies: 1
    Last Post: 06-12-2014, 10:56 PM
  2. 325e Fuel pressure?
    By 321demot in forum 1983 - 1991 (E30)
    Replies: 1
    Last Post: 09-10-2012, 08:00 AM
  3. summary: fuel pressure regulator replacement
    By cek2 in forum 1991 - 1999 (E36)
    Replies: 3
    Last Post: 09-22-2003, 10:18 AM
  4. WTB 325e fuel pressure regulator
    By wicked in forum BMW Parts Wanted sponsored by Bavarian Auto Recycling
    Replies: 0
    Last Post: 01-23-2003, 05:12 PM
  5. help: Fuel Pressure Regulator or Larger Injectors
    By M3RCR in forum 1992 - 1999 M3 (E36)
    Replies: 1
    Last Post: 05-01-2001, 09:30 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •