Possible Fuel Leak... Opinions Needed

Discussion in 'Performance & Fuel' started by sdavis2702, Dec 2, 2008.

  1. sdavis2702

    sdavis2702 Rockstar 100 Posts

    I used the search feature... my question is just a little more specific.

    Today I had my fuel pressure checked because I have some hard starts and some rough idling going on with my 2000 Silverado 5.3L. Well after testing some codes I got that it was a random misfire or possible vacuum leak. It's not a vacuum leak.

    Today when I had the pressure checked, it would immediately jump to 55psi like it should, but it took a whopping 20-30 seconds to slowly lower to about 10psi. Take the key out, turn it on again, same thing. The guy that was helping me says that the constant drop after going to where it's supposed to be usually means there is a fuel leak.

    We checked the fuel lines where possible. No leaks between the tank and the transmission, which is where we lost visibility. However, we didn't smell a darn thing in the engine bay.

    With the pressure jumpin to where it's supposed to, could my fuel pump be bad?

    Could I have a leak IN the tank?

    Any suggestions or ideas?
  2. ct9a

    ct9a Epic Member 5+ Years 1000 Posts

    My first guess would be the fuel pressure regulator.
  3. retired

    retired Rockstar 100 Posts

    You could have a stuck pressure regulator? But is the pressure drooping while it's running? Here's what I would do, pull the oil dip stick it you smell a lot of gas on it you know you have a stuck pressure regulator or a bad injector. If it's running and fuel pressure drops replace the fuel filter. Replace the filter anyway when was the last time it was replaced.
  4. sdavis2702

    sdavis2702 Rockstar 100 Posts

    I replaced the fuel filter literally 2 days ago. It was tested without the truck running. We hooked it up, turned the key to run but not start. When the pump kicked on, psi jumped to 55. Then it took a quick drop to 50... then slowly down to ten. Never tested it while the truck was running.

    Where is the pressure regulator and is it something I can replace?
  5. ct9a

    ct9a Epic Member 5+ Years 1000 Posts

    Pressure regulator is replaceable, in fact, they make aftermarket adjustable ones for performance.

    It may also be an injector that is stuck open. Unfortunately, I don't know the layout of a 5.3L, so I can't tell you much more.
  6. MrShorty

    MrShorty Epic Member 5+ Years 1000 Posts

    FPR is one possibility. Usually in this scenario, the leak is through the diaphragm, and unmetered fuel is "leaking" into the intake, causing the misfires/rich condition. I'm not certain of the layout on your 5.3, but I thought it was similar to my '98 5.7, where the FPR is attached to the "fuel meter body" (aka CSFI unit, aka injector spider) inside the upper intake. They say that you can check for this scenario by looking down the throttle body for gasoline or "clean" streaks that indicate gasoline is leaking out of the FPR into the intake. If your 5.3 is laid out like this, then this should work.

    The other common "leak" that causes the fuel pressure to bleed off like is through the check valve in the pump. The check valve is there to prevent fuel from draining back into the tank when the pump isn't running. When the check valve goes bad, the pressure drops as the fuel drains back into the tank.
  7. sdavis2702

    sdavis2702 Rockstar 100 Posts

    Awesome thanks for the answers guys. I really need to narrow this down so I appreciate all of the responses.
  8. sdavis2702

    sdavis2702 Rockstar 100 Posts

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