Need some assistance for 5.3 swapped truck

Discussion in 'High Tech Retrofits' started by Sir 4 speed, May 20, 2020.

  1. Sir 4 speed

    Sir 4 speed Veteran Member

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    My Dad bought a 1950 pickup with a 5.3L swap. Truck had a stumble while driving checked fuel pressure and it was low as well as the pump was louder than normal. He changed the pump and added in new filters (1 post pump and 1 pre pump). The pump is not in the tank. Runs good and all however when it gets warn it starts running choppy again. New filter and better but not 100%. At idle it shows 45psi at the rail, when he revs the engine it drops some. At about 3500 rpm it starts to stumble again. It still has the old style metal gas cap and has a vent hose on top of pump but wondering if it could be a vapor lock issue or anything anyone else may have the knowledge about. I know the injectors require a specific psi to operate normal but unsure of the exact spec. Thanks, Oh and here are some pics of the truck 20200514_182545(1).jpg 20200510_182602.jpg
     
  2. Green hornet

    Green hornet Veteran Member

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    I may be wrong and others will chime in but I believe the fuel pressure is low. I think it’s supposed to be 60+ psi from what I remember.
     
  3. Pierre74LT

    Pierre74LT New Member

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    the fuel pressure should be higher 385–425 kPa (55–62 psi)
     
  4. mrfleet12

    mrfleet12 Veteran Member

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    Great looking truck.
    As others have mentioned pressure seems low, mine starts just over 58 and no issues.
    What controller are you running?
     
  5. camarochevy1970

    camarochevy1970 Veteran Member

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    right, you want to keep that at 58ish psi. If it drops when you hit the gas it won't run right. If you have already done filters, time to look at the pump
     
  6. John Wright

    John Wright Veteran Member Lifetime Gold Member

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    Does it sound like it has a vacuum in the tank when you take the gas cap off the tank while it's running? May have a venting problem if using the old factory 50's tank. I also agree with the others that the fuel pressure should be a minimum of 53-55psi or so.
     
  7. Sir 4 speed

    Sir 4 speed Veteran Member

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    Pulled filter off again as new pump was getting loud... found quite a bit of rust particles in it. Looks like a new pump and tank is going in it this weekend. My Dad already ordered them. We believe the junk from inside the tank overworked the pump and cause the pressure to drop.
     
    mrfleet12 likes this.

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