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Thread: Fuel pressure

  1. #1
    Join Date
    Aug 2018
    Location
    NH
    Posts
    13

    Default Fuel pressure

    Hi all,
    I just had the fuel pump replaced under the recall. Even though the time frame passed since it was never done on my car they paid for it all. But, I just got the vehicle back from the dealer and I noticed it starts real hard (meaning I have to let it crank over 8-10 times before it will start). The service manager told me that the fuel pump is getting broken into the engine, or air in the lines. The car runs great once it is running, I have driven it for two days and still have the hard starting issue. I did a little troubleshooting myself. With the engine running my fuel pressure is around 55psi @ the fuel rail, when I shut the engine off the pressure drops to 0psi within a couple of minutes. I did not have this issue with the old pump, and I have an appointment to go back to the dealer. I was wondering if anyone had any further troubleshooting ideas/tips to narrow the problem to the pump or another component.

    Thanks

  2. #2
    Join Date
    Feb 2013
    Location
    Boston, MA
    Posts
    1,011

    Default

    Quote Originally Posted by gtacs View Post
    Hi all,
    I just had the fuel pump replaced under the recall. Even though the time frame passed since it was never done on my car they paid for it all. But, I just got the vehicle back from the dealer and I noticed it starts real hard (meaning I have to let it crank over 8-10 times before it will start). The service manager told me that the fuel pump is getting broken into the engine, or air in the lines. The car runs great once it is running, I have driven it for two days and still have the hard starting issue. I did a little troubleshooting myself. With the engine running my fuel pressure is around 55psi @ the fuel rail, when I shut the engine off the pressure drops to 0psi within a couple of minutes. I did not have this issue with the old pump, and I have an appointment to go back to the dealer. I was wondering if anyone had any further troubleshooting ideas/tips to narrow the problem to the pump or another component.

    Thanks
    Did you measure how fuel pressure builds up on start?
    2002 V70 (sold)
    2005 XC70 (Telos Road took it. Did a chassis swap)
    2016 XC60

  3. #3
    Join Date
    Aug 2018
    Location
    NH
    Posts
    13

    Default

    vtl,
    yeah after the car starts the pressure is about 55psi but drops to 0psi in a couple minutes.

  4. #4
    Join Date
    Feb 2013
    Location
    Boston, MA
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    Default

    Quote Originally Posted by gtacs View Post
    vtl,
    yeah after the car starts the pressure is about 55psi but drops to 0psi in a couple minutes.
    I'm talking about how it develops/builds up before engine starts. Attach the gauge, key in position II, observe.

    Also it may help if you switch key between II and I a few times. Give it 5 seconds in II, move back to I, repeat. Fuel pump works a few seconds in II, but it may not be able to build enough pressure if there's a leak.
    2002 V70 (sold)
    2005 XC70 (Telos Road took it. Did a chassis swap)
    2016 XC60

  5. #5
    Join Date
    Aug 2018
    Location
    NH
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    Default

    I see, I'll check that tonight. Could I hook a compressor up to the schrader valve and pressurize the system up to around 50psi and check for leaks? Would this yield any valuable information?

    Thanks

  6. #6
    Join Date
    May 2012
    Location
    Calgary, Alberta
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    582

    Default

    Quote Originally Posted by gtacs View Post
    I see, I'll check that tonight. Could I hook a compressor up to the schrader valve and pressurize the system up to around 50psi and check for leaks? Would this yield any valuable information?

    Thanks
    I suspect that that would be a bad idea. The system is supposed hold pressure in it after it is shut off. If it is dropping to zero with in minutes there is a problem.

  7. #7
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    Feb 2013
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    Boston, MA
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    Default

    Quote Originally Posted by gtacs View Post
    I see, I'll check that tonight. Could I hook a compressor up to the schrader valve and pressurize the system up to around 50psi and check for leaks? Would this yield any valuable information?

    Thanks
    No, don't do that. I don't know if your model year has a fuel return line or PEM-controlled fuel pump, but fuel release valve is not holding up the pressure. Latter case (PEM) would mean the pump was installed improperly.
    2002 V70 (sold)
    2005 XC70 (Telos Road took it. Did a chassis swap)
    2016 XC60

  8. #8
    Join Date
    Feb 2010
    Location
    Virginia Beach
    Posts
    3,639

    Default

    Quote Originally Posted by gtacs View Post
    I see, I'll check that tonight. Could I hook a compressor up to the schrader valve and pressurize the system up to around 50psi and check for leaks? Would this yield any valuable information?

    Thanks
    You only hook up a fuel pressure gauge - that's what the schrader valve is for... And if it's not holding pressure, then go looking for leaks.

    If you don't smell fuel, already, though, I doubt your system is leaking anywhere other than the pump itself.

    Since the problem started with the new pump, I would be asking the dealer to fix what they "fixed"...
    Current Fleet:
    2016 Tundra Crewmax 4WD 1794
    2005 MB S600 (96K, Michelin AS3, M1 0W40)
    2002 V70-XC (233K, AltiMax RT43, Castrol Edge 0W40)
    2002 V70-T5 (195K, IPD bars, Bilsteins, Contis, Mobil 1 0W30)
    1932 Packard Sedan (straight 8, dual sidemounts, original paint and interior, Shell Rotella 15W40)

  9. #9
    Join Date
    Aug 2017
    Location
    Pleasanton CA USA
    Posts
    177

    Default

    There is a check valve in the fuel pump that only allows flow in one direction. When the pump shuts off (engine off) this check valve is supposed to close tight, and this keeps
    the fuel pressure at the manifold so that the car will start quickly.

    The loss of fuel pressure back down to 0 within a few minutes after shutoff, combined with no fuel odor, points strongly to you have been given a defective fuel pump.

    Take the car back to the dealer with your fuel pressure measurements, and ask for a new fuel pump, one that can hold backpressure when the engine is off.

  10. #10
    Join Date
    Oct 2018
    Location
    Chattanooga TN
    Posts
    3

    Default

    There is a recall? I have been out of the loop for a few years but just picked up a 2006 xc70 that is throwing a CEL that is fuel pump related. My mechanic to.d me it is not giving the right pressure or the pressure varies or something like that. My car drives fine 99 percent of the time but does stall sometimes ona cold start. It can stumble as well on a cold start. Where can I find more info on this? Thanks
    2006 xc70 willow green 256k miles

    2016 VW Golf sportwagen 31k miles
    2017 Nissan Rogue SV 18k miles

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