Crank, no start, pump running but no fuel at the shredder valve

Discussion in 'Engine & Drivetrain' started by Herb Rodriguez, May 9, 2018.

  1. Herb Rodriguez

    Herb Rodriguez TYF Newbie

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    So I have an 03 Yukon XL, 5.3 flex fuel. While I was out of town the wife ran it out of gas. I've added 5 gallons of gas but no start. I can hear the pump running for a few seconds and what sounds like a lot fuel returning (splashing) to the tank. I squirted fuel in at the throttle blade and the engine runs until the fuel is gone. When I push the shradder valve in there is no fuel at the fuel rail. I've owned the truck for 18 months and replaced all filters when I bought it.

    Could the regulator be malfunctioning and returning all the fuel to the tank? If so, how can I test that? It pulled a code for MAS but I think that is because I disconnected the intake plumbing to inject fuel at the throttle blade.

    Maybe I should just start with disconnecting the fuel line at the filter and see if fuel is flowing there. Maybe the fuel was so low it lost prime. Shouldn't it gain prime easily after adding fuel?

    I'm grasping for answers here but i guess I'm going to have to push this heavy beast to my shop around back and get under it.

    Thoughts from others? Thanks in advance!
     
  2. drakon543

    drakon543 Full Access Member

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    running a tank out of gas can cause several problems. when you run a tank out of gas when you put new gas in you can disturb any sediment in the tank which can be picked up by the pump. also there are flex hoses that connect the pump module itself to the solid lines. that is unrelated to running it out of gas but if one of those lines breaks the pump will run but it wont get fuel to the engine. also yes your question about the regulator is correct to my knowledge.
     
  3. Doubeleive

    Doubeleive Elite Member Supporting Member

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    I wonder if you could just disconnect the line at the fuel filter and connect one of those little $25 hand vacuum/transfer pumps to the line and suck some fuel up to the filter? that would resolve any "prime" issue I would think anyway, there all plastic so no chance of anything sparking. just an idea

    might have to be turning the key on at the same time to make it work, if that fails it might be time for a new fuel pump.
     
  4. swathdiver

    swathdiver Full Access Member

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    Press in the schrader valve while a helper turns on the ignition and the pump primes the rail, getting the air/blockage out. Does that model have a fuel pressure regulator on the rail? If so, pull the vacuum line and see if there's fuel on that side of the diaphragm.

    Should be codes thrown for this.
     
  5. drakon543

    drakon543 Full Access Member

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    priming a fuel pump is not needed only on diesels. if you have prime a gasoline fuel pump you have other issues inside the pump. just disconnect the fuel line from the fuel filter and stick it in a bucket. if the fuel pump working correctly you will get significant fuel spray coming out of the line. if you get nothing or weak flow you have a problem with the pump. if you get a good spray from the line you have a problem farther down.
     
  6. drakon543

    drakon543 Full Access Member

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    swath is also correct normally an air pocket will just be pushed out by the pressure but ive heard rumors of this occuring before. also as far as im aware the regulator is electronic on this model so you may not be able to test with his methis. 03 style montecarlos are known for the regulator leaking internally.
     
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  7. Herb Rodriguez

    Herb Rodriguez TYF Newbie

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    Thanks everyone for all the suggestions! I did try the easy things first; it wouldn't start while pushing in on the shrader valve and my vacuum actuated pressure regulator doesn't have fuel on the vacuum side. First thing in the morning I'm going to try to push the truck around back and disconnect the fuel line before the filter and see if I have fuel flow during key on (prime). I'll let you know how it goes
     
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  8. Rocket Man

    Rocket Man Sometimes A Dumbass Supporting Member

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    Subbed for results
     
  9. Herb Rodriguez

    Herb Rodriguez TYF Newbie

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    I'm pleased to report that a new fuel pump fixed the problem. I could hear the pump running/priming so I initially didn't think the pump was at fault but a new pump from O'Reillys Auto Parts got it started and running fine. Thanks for all the input from everyone. Big lesson learned for my wife, to not let the fuel get so low....on any vehicle.

    Now to think about upcoming road trips for the summer. Hopefully gas won't go above $3 per gallon as some suggest!
     
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  10. Rocket Man

    Rocket Man Sometimes A Dumbass Supporting Member

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    Good to hear it's fixed. I'm already paying $3.50 a gallon for the premium I run.
     
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