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  1. #1
    Sr. Engineer FergusonT's Avatar
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    Default '99 5.3 silverado fuel pressure

    Ok...So I get 55-58psi with the key on/engine off, for about 2 seconds while the pump is on. as soon as the pump stops it drops do about 52psi. the truck refuses to start. Cranks fine, and seems like its about to start but just dies.
    1999 Chevrolet Suburban LS K1500
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    2005 Suzuki Forenza (GM/Daewoo)

  2. #2

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    What is the fuel pressure doing while it is trying to start? Does it stay down near 52, drop further, or does it come back up to 58? If you jumper the fuel pump test lead (labeled "fuel pump prime connector" in Chilton's wiring diagram and is a red wire coming out of the power distribution box that just dead ends. If you apply power to this lead, the pump will run continuously), does the pressure stay up near 60, or does it drop off while trying to start?
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  3. #3
    Sr. Engineer FergusonT's Avatar
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    the pressure stays up while its trying to start, only drops down when the pump stops running as far as I can tell. I can try the jumper on the fuel pump test lead. Where is it located.

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    PRESSURE is low for a cold start. make sure the gage is not inaccurate. is the needle on zero when off. if its above zero this may be showing more than what you have. droping a few psi is normal on pump shutdown however the pressure is low for a cold start in the temps you now have outside.

    it only takes a little bang to throw the gage cal off.

    with a spark plug connected to the ignition wire [spare plug] see if you get a spark when cranking. ground the plug body secuely. should be blue.

  5. #5
    Sr. Engineer FergusonT's Avatar
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    actually i just pulled the fuel filter off, it looks old and a bunch of black stuff came out of it when I pulled it...so I am about to run to the parts store and grab a filter.

    - - - Updated - - -

    The gauge is good, sits at zero. I just bought it today

  6. #6
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    a restricted filter will reduce flow . this will cause a low pressure on a cold start.

    I don't like the black stuff comment. that should not be black. I never seen black. you think you may have had some one screw with you fuel ?

    a dirty filter you would get a rust/red type of color.brown color. sometimes with alcohol white looking stuff in the fuel.

    put a hose on the filter pipe from pump direct into the bucket check for contamination . key on will only run 2 sec see what you get before the new filter hook up.

  7. #7
    Sr. Engineer FergusonT's Avatar
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    I can't imagine anybody would mess with the truck, I live way out in the country for one, don't have any enemies where I work.....but who knows about people man...look what happened at that school. I normally get gas from decent gas stations, not ma/pa type places, dont think that would matter anyways.

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    anything is possible. the other day a gasoline tanker filled a gas station with jet fuel . vehicles did not get very far .

    check fuel before new filter install just to be sure. if the fuel is bad you have a lot of work to do sucking it all out then drop tank and clean up.

  9. #9
    Sr. Engineer FergusonT's Avatar
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    right, thanks for the heads up

    - - - Updated - - -

    actually....im just remembering, I just tested the fuel pressure with a gauge, the bleed off hose is clear and the fuel didn't look abnormal.

    - - - Updated - - -

    replaced fuel filter, now fuel pressure down to around 20psi

  10. #10

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    20 psi is definitely too low. Have you allowed the pump to run long enough to fill the filter? Another test that is indicated with low fuel pressure is to clamp off the return line and run the pump. If the pressure is still too low, that indicates that the pump is bad. If the pressure jumps up when clamping off the return line, that indicates a bad FPR. Have you tried starting with starter fluid?

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