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Fuel Pressure Woes

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by WyomingBurb, Jul 10, 2012.

  1. WyomingBurb

    WyomingBurb New Member

    85 k10 350 700r4

    I had a small inline carter fuel pump that was only putting out 3 lbs of pressure (rated at 5-7lbs)... so... i went and put a new bigger carter fuel pump and it does the same thing (rated 5-9lbs with much higher gph rating)... NO DIFFERENCE... ugh!!!!!

    All my lines are tight with no leaks, the truck starts up fine, drive through WOT fine, just.... not right? Any ideas...
  2. Crawdaddy

    Crawdaddy Moderator Staff Member Platinum Contributor 1000 Posts 100 Posts

    If you're not getting the pressure you expect and it's a good pump, it sounds like you have some sort of restriction in your fuel system. Perhaps a clogged fuel filter or other blockage in the fuel line that's limiting pressure. Start at the tank and pump, and move forward towards the carb. Also, if you have a fuel return line, that could be clogged causing the fuel restriction. If it's only happening when the engine's warm, it could be that you have a vaporlock issue.
  3. WyomingBurb

    WyomingBurb New Member

    I think im going to check the sock on the fuel line in the tank and see how bad it is... not sure but im pretty sure its original. Can i blow out fuel lines with compressed air???

    i get 3 lbs cold or hot now... really annoying
  4. bazar01

    bazar01 New Member 100 Posts

    You sure you don't have a pressure regulator downstream prior to carb?

    Pressure is restriction to flow, that is if the supply volume flow is a lot greater than the consumption, which will normally require a return line.
    If the return line is restricted, that will build up pressure.
    If the suction line is blocked, then volume flow is less which will reduce pressure assuming consumption does not change.
  5. tbplus10

    tbplus10 Super Moderator Staff Member Platinum Contributor 1000 Posts 100 Posts

    Check your return line and charcoal canister if you have one, this sounds like you fuel pressure is being limited by backpressure.

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