5.7 Vortec: Intermittant start failure.

Discussion in '96+ Vortec Performance + Computer Swaps' started by TwistR, Mar 31, 2021.

  1. TwistR

    TwistR Newbie

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    I have a 96 K2500 5.7 Vortec that was running perfectly. However, for the past week, it starts up normally but when I try to start it when it's warm after it's been off for 5 mins, it won't fire, it just cranks. When I release the ignition it will fire and choke a little sometimes. I'm not touching the gas. I've found that to get it started, I have to press the gas to about 3/4 and then it will start to fire, sputter, then start. It will run rough, then hesitate if I hit the gas hard. After a while, no hesitation on the hitting the gas hard. It's back to running normally. It's almost like it's a flooded carb.

    I replaced the fuel filter 6 months ago. The rest of the truck is original and it has about 160k miles on it. Does a fuel pump behave like this before it failsl sometimes? Injectors? I will be replacing the dist cap, rotor, wires and spark plugs in a month or so.

    No codes. TIA.
     
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  2. east302

    east302 I'm Awesome

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    Holding the gas down is “clear flood” mode as it temporarily stops injector flow.

    If you have a scanner, see what the engine coolant temperature sensor is reporting. It should be ambient when cold, 190-ish when hot.

    A fuel pressure test wouldn’t hurt. Could be a leaking injector.
     
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  3. stutaeng

    stutaeng I'm Awesome

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    Probably injectors and/or FPR leaking down after warm shutoff and flooding the engine. As @east302 pointed out, holding the gas down will clear the flood. Are they the original?

    Pretty easy to diagnose FPR with a basic fuel pressure guage. Injectors need an injector balance test. Diagnose properly before changing it, and go with the MPFI upgrade unit.

    Good luck.
     
    Last edited: Mar 31, 2021
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  4. GoToGuy

    GoToGuy OBS Enthusiast

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    Have you done the injector spider conversion?
     

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