Fuel pressure test result today

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by bazar01, Sep 15, 2012.

  1. MrShorty

    MrShorty Epic Member 5+ Years 1000 Posts

    That's certainly one way of blocking off the return line. Some don't like it because of the possibility of damaging the hose. But, as long as you are careful of that possibility, it should give you an indication if the regulator is stuck open.
  2. dpeter

    dpeter Epic Member 5+ Years 500 Posts

  3. Shicuppycep

    Shicuppycep New Member

    Fuel pressure

    There is a fuel pressure fitting on the fuel rail, that looks like a tire valve, and is used to test the fuel pressure with a gauge. The best way to depressure the system is to start the truck and pull the fuel pump fuse.regardsrikard
    Last edited by a moderator: Sep 17, 2012
  4. bazar01

    bazar01 Rockstar 100 Posts

    Got it dpeter. I appreciate the explanation.

    I just got home from work and don't think i can perform the test tonight. How hard is it to disconnect the return line? I see a clip holding the flex line to the rail return. Is it just a matter of separating the two once the clip is off?

  5. bazar01

    bazar01 Rockstar 100 Posts

    I tried to disconnect the return line shown in the picture above. I pried the clip up and moved it back and it came off. Then I tried to pull the flex line off the rail line but it seemed like there is another clip inside that holds it in place.
    I researched and found a fuel line disconnect tool for 5/16" and 3/8" fuel line. I will try it again tomorrow night.
    Here is the tool.
    disconnect tool.jpg
  6. bazar01

    bazar01 Rockstar 100 Posts

    Got the return line off.
    Return line off.jpg

    This tool did it.

    I plugged the line with a crimped rubber hose with no hose clamp. When I turned on the ignition switch ON, pressure rose to 55 psi and it blew the plug off. The regulator is leaking.

    With just a clear hose on the return line, fuel leaked out and pressure only rose to 44 psi.

    Now I am sure the regulator is bad. I will just go to a dealership and get the factory regulator to be safe.

    Thanks for the help dpeter.
  7. bazar01

    bazar01 Rockstar 100 Posts

    Well, it turned out to ba a bad fuel pump check valve.

    I changed the fuel pressure regulator but the fuel rail was still losing pressure. It was still dropping to zero psi after 2 minutes.

    Today, I changed the fuel pump and the fuel pressure held at 50 psi even after 10 minutes. It took me 2 hours to drop the 1/8 full fuel tank, pull the old pump, install the new pump and re-install the fuel tank. The new fuel pump was so quiet I could not even hear it running compared to the old one that was humming real loud.
  8. bazar01

    bazar01 Rockstar 100 Posts

    This is how the factory fuel pump looks.



  9. dpeter

    dpeter Epic Member 5+ Years 500 Posts

    Issues with more than one problem contributing can be REAL buggers to get sorted out. Happy to hear you got it resolved. I do have a question for you though. Did you replace the regulator and if so, what were those pressures after replacement and did it run OK?
  10. bazar01

    bazar01 Rockstar 100 Posts

    Yes I changed the regulator, that was the fisrt thing I did, since I really did not feel like changing the fuel pump. Pressure went up to 50 psi, but it was still bleeding off to zero after 2 minutes. The moment the pressure dropped to zero, I got kind of disappointed since I knew there was only one thing left unchecked which was the check valve on the fuel pump.
    I ended up buying a new fuel pump.

    What can make the check valve go bad?
    Worn spring or ball maybe that are internal to the check valve maybe?

    There must a be a way to install an external check valve so we don't have to replace the in-tank fuel pump.

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