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  1. #11

    Default

    How about just pinching the return line with a vice grip or something?
    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.
    '98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
    '92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
    "My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World

  2. #12
    Sr. Engineer
    Join Date
    Oct 2010
    Location
    Indianapolis, In
    Posts
    487

    Default

    [QUOTE=bazar01;507682]But isn't it that there will be fuel coming out of the return line no matter what with engine OFF or ON. Excess fuel has to come out to maintain set pressure. Isn't it that the fuel pump has more volumetric capacity than what the engine needs, that's why there is a return line and that's why I wanted to block it off and see if the pressure rises to 55 psi and holds, but I could be wrong.


    The point I was tying to make was to take the pressure reading in conjuntion with the observation of fuel flow from the return. If there is no return flow, then the regulator is trying to keep the pressure up by not allowing any return and if the pressuere is not up to spec., it is the fault of the pump. If on the other hand it is returning fuel AND the pressure is not up to spec. , then the regulator is likely at fault.
    2000 GMC YUKON SLT, 5.3L tow pkg, G80 rear/w 3.73 gear

  3. #13

    Default 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 tbplus10; 09-17-2012 at 08:36 PM.

  4. #14

    Default

    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?

    Click image for larger version. 

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    2011 Chevy Silverado LT 4WD 25k miles
    2001 Suburban 2WD, 5.3, V8 176k miles
    1993 964
    1996 318TI

  5. #15

    Default

    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.
    Click image for larger version. 

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    2011 Chevy Silverado LT 4WD 25k miles
    2001 Suburban 2WD, 5.3, V8 176k miles
    1993 964
    1996 318TI

  6. #16

    Default

    Got the return line off.
    Click image for larger version. 

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    This tool did it.
    Click image for larger version. 

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    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.
    2011 Chevy Silverado LT 4WD 25k miles
    2001 Suburban 2WD, 5.3, V8 176k miles
    1993 964
    1996 318TI

  7. #17

    Default

    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.
    2011 Chevy Silverado LT 4WD 25k miles
    2001 Suburban 2WD, 5.3, V8 176k miles
    1993 964
    1996 318TI

  8. #18

    Default

    This is how the factory fuel pump looks.

    Click image for larger version. 

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    2011 Chevy Silverado LT 4WD 25k miles
    2001 Suburban 2WD, 5.3, V8 176k miles
    1993 964
    1996 318TI

  9. #19
    Sr. Engineer
    Join Date
    Oct 2010
    Location
    Indianapolis, In
    Posts
    487

    Default

    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?
    2000 GMC YUKON SLT, 5.3L tow pkg, G80 rear/w 3.73 gear

  10. #20

    Default

    Quote Originally Posted by dpeter View Post
    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?
    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.
    2011 Chevy Silverado LT 4WD 25k miles
    2001 Suburban 2WD, 5.3, V8 176k miles
    1993 964
    1996 318TI

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