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fuel pump stays on after shut-off??

Discussion in 'The Garage' started by complexmar, Sep 8, 2005.

  1. complexmar

    complexmar Registered Member

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    I just finished sawpping a new engine/tranny into my '88 k5 and everything seems to be working great except when I shut the engine off the fuel pump stays on for about 4 seconds. I don't remember it doing that before. When I just turn the key on with out starting it the pump builds pressure (as normal) and I can stop it by keying off which tells me that power is being cut by the ignition. I just dont see why it would do that after I shut it off.....

    is that normal and i'm just noticing it because I'm looking for problems or is something wrong?
     
  2. 1979jimmy350

    1979jimmy350 1/2 ton status

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    i have no idea what is causing it but mine and my friends Blazers do the same thing and my friends blazer has been rewired totaly and every thing is the way it was stock
     
  3. mikey_d05

    mikey_d05 1 ton status GMOTM Winner

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    My '89 does it and I haven't messed with that portion of it's wiring...has ever since I bought it.
     
  4. 88sub4x4

    88sub4x4 1/2 ton status

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    Yeah, thats normal. All fuel injected GM's do that from 87 until present day. Just the design to make sure the proper fuel pressure is present when the next start-up comes.
     
  5. complexmar

    complexmar Registered Member

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    ok, so no worries then. whew

    thanks!
     
  6. BigOrange90Jimmy

    BigOrange90Jimmy 1/2 ton status Premium Member

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    Hmm...then something WAS wrong with my orange truck. The fuel pump NEVER primed after shut-down.
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Your pump should run, then shut off after about 2 seconds if you key on/engine off. If it doesn't, somethings wrong.
     
  8. rcurrier44

    rcurrier44 1/2 ton status

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    Many cars do that to cycle hot fuel back to the tank. This brings in cool fuel and prevents vaprolock/help the motor start quicker.
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    Fuel injection does it to reduce cranking time as well. Which is one of the reasons you should let the pump run before you try and crank it.
     
  10. The Butcher

    The Butcher 1/2 ton status Premium Member

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    If the pump starts to stay on longer and longer before shutting off, you will probably be needing a new fuel pump before long. This happened to my '99 3/4ton burb, as well as my buddy's tahoe. Seems like right before they go out they start to stay on longer and longer. Went from the normal 2-3 seconds up to about 5 or 6 seconds. Fuel pump went out about a month after starting that little habit.
     
  11. mikey_d05

    mikey_d05 1 ton status GMOTM Winner

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    Probably from the seals or motor going bad, not enough pressure to shut it off.
     

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