Results 1 to 4 of 4

Thread: fuel pressure issue, which part will need replacement?

  1. #1
    Join Date
    May 2004
    Location
    Belgium
    Posts
    2
    My Cars
    e36

    fuel pressure issue, which part will need replacement?

    My e85 3.0 (m54) started to show issues with starting the last months. Cold start is perfect, it runs fine, no hesitations, just a fine ride.
    But when driven a few miles and letting the car sit for 1 hour it takes a long cranking before the car wants to start. Lets say 5 seconds of cranking which normaly was less then 1 second.

    I started searching the forum and found several possible issues: Leaking injector, problem with check valve, regulator, fuel filter and pump issues.

    Today it even had then worst start ever and it took 10s of cranking, it would not start, but when I stopped cranking and tried the second time it fired right up. And when it starts it runs perfect, no hesitation or nothing.

    What I already tried:
    - camshaft position sensor replaced a few weeks ago (even before the issue started).
    - code reading: no codes found
    - (longer) priming before starting --> no difference
    - checked fuel pressure and there it gets weird.


    When first connecting the fuel pressure gauge to the fuel rail and priming it goes to 40 psi, then starting, fires right up and runs on 50ish psi. So far so good.
    Then letting the car sit for 30 minutes the pressure dropped to +- 35 psi, not bad I think. But when starting the car it takes a long start, during priming the psi does not go up and during idle or even mildly reving the pressure stays at 35psi.
    Then I stopped the car and relieved the pressure completely. Now when priming it hardly gets to 20psi, has a long crank, fires up and stays around 20 psi.

    So I think I have clearly a fuel pressure issue but what is causing this, what is the first suspect and how to test?

    I would guess either the fuel filter is clogged, the fuel pressure regulator is not working or the fuel pump is dying. Could anyone give me directions where and how to start?
    Last edited by peerware; 07-29-2022 at 03:10 PM.

  2. #2
    Join Date
    Oct 2012
    Location
    Victoria BC Canada
    Posts
    378
    My Cars
    2004 Z4, 1700 Nomad MC
    Well… the fuel pump/filter is in the gas tank and to remove it requires that the tank be empty….. so if you are planning on replacing the fuel filter and possibly the pump, make sure that it’s as close to empty as possible.

    Personally, if no codes are showing, I’d go change the fuel filter and pump (you are already in there no change in labour cost) and then see what happens.

    I’ve had a filter issue on a previous vehicle and long cranking second time around was a symptom if I recall correctly… was a very long time ago and I’m old now…. Lol


    Sent from my iPad using Tapatalk

  3. #3
    Join Date
    May 2004
    Location
    Belgium
    Posts
    2
    My Cars
    e36
    Is there an easy way to drain the tank, or should I disconnect a fuel line and jump the relay of the pump?

    I was looking in the history and I cannot see any fuel pump replacement in the documentation. De Z4 has 170.000 miles and is now 19 years old so replacing the pump might be a good idea anyway.

    Should I go OEM or are there better pumps and filters on the market?

  4. #4
    Join Date
    Oct 2012
    Location
    Victoria BC Canada
    Posts
    378
    My Cars
    2004 Z4, 1700 Nomad MC
    I had mine done by a independent shop… it was put on a hoist… and the “port” into the gas tank is on the bottom of the tank so they cracked it open slightly so it leaked with a container/pan/ to catch the gas….

    Really don’t recommend doing this as a DIY with the carjacked up……


    Sent from my iPhone using Tapatalk

Similar Threads

  1. Fuel Pressure Issue, need advice
    By ckwinter in forum 1975 - 1983 (E21)
    Replies: 121
    Last Post: 04-11-2015, 01:09 AM
  2. FPR Fuel Pressure Issues
    By VINCE325 in forum 1983 - 1991 (E30)
    Replies: 13
    Last Post: 10-16-2008, 11:16 PM
  3. Fuel pressure issue
    By VINCE325 in forum 1983 - 1991 (E30)
    Replies: 13
    Last Post: 09-06-2008, 01:25 PM
  4. Fuel Pressure Issue
    By downeaster1 in forum 1991 - 1999 (E36)
    Replies: 15
    Last Post: 06-20-2008, 03:08 PM
  5. '00 528iT Fuel pressure issues ...
    By jase007 in forum 1996 - 2003 (E39)
    Replies: 3
    Last Post: 07-26-2007, 04:05 PM

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
  •