fuel pump problems ?

Discussion in 'General Chevy & GM Tech Questions' started by RATRODKING, Aug 15, 2010.


    RATRODKING Rockstar 100 Posts

    guy, i have a strange one for you.

    1 year and 9k miles ago i had the fuel pump and relay replaced in my 1990 k-1500 4x4.

    its been running perfect until last night.
    i went to park on a slight hill, had to put it in 4 wheel low to get up it, once at the top i got the truck level and stayed in the truck with it running while talking on my cell phone for 5-10 minutes. turned the truck off, got out while waiting on a buddy to show up, and after 10 minutes decided to start the truck again and get some a/c while waiting for him to show up. thats when the truck didnt start. tried like 5 different times, and nothing. it would turn over fine, but wouldnt start.
    took the gas cap off, turned the key on, and couldnt hear the pump run for the 2-3 seconds that it usually does.
    tried that a few more times, then got the pump to run for the 2-3 seconds after the key was turned on, but the truck still would not start.
    i pulled a spark plug wire off to check for spark, and it was getting really good spark.

    started arranging for a tow truck, calling some friends, and decided to pull the relay connection off, and re-plug it back in, and did the same to the fuel pump fuse on the firewall near the a/c, under the black plastic cover. then tapped on the throttle body with a ratchet handle, got in the truck and it fired right up.... turned it off 2 more times and it started both times.
    when my buddy showed up i wanted to show him it now starts, and it would not start..... very frustrating.
    waited about 30-45 minutes, went back out to the truck, turned the key, and it still would not start up.
    decided to unplug the fuel pump relay and fuse again, plug them both back in, tap on the throttle body again with the ratchet, and it fired right up.....
    not wanting to jinx it, i turned it off and and hung out with my friends for about 3 hours.
    when i wanted to go home, i turned the key and it fired right up and got me home with no problem.

    so, do you guys have any ideas on what might be the problem ?
    for the heck of it i am gonna see if autozone will give me a new fuel pump relay and go from there. kind of hard to bring to a mechanic to diagnose if its running good.

    this one has got me stumped. oh yea, and it has a complete tune up with plugs, wires, rotor, cap, coil, and ignition module, all with 20k miles and 2 years on them.

    thanks for the help.


    ---------- Post added at 07:05 AM ---------- Previous post was at 07:02 AM ----------

    oh yea, its got a 5.7 v-8 with 130k original miles.
  2. MightyMax

    MightyMax Rockstar 100 Posts

    Sounds like my problem. Let me know what you figure out. :D
    A lot of what you replaced, is what I have replaced.....

    Things I still need to look at on my check list is::
    Fuel Pump Relay
    ECM (perhaps)

    Can you see if the injectors are spraying fuel?

    Fuel Filter would be another place to check.

    RATRODKING Rockstar 100 Posts

    im going outside now to mess with it and will let you know.
    yes, i also did the fuel filter when i did the pump.
    if it starts i will look at the injectors, but if running they will obviously be spraying.
    even if the truck does start, im gonna replace the relay and go from there. i gotta replace something.
    just hope it aint my pump starting to go.

    so, your truck does the same thing ? how long has yours been doing this ? is yours currently running good ?

  4. MightyMax

    MightyMax Rockstar 100 Posts

    Yep, just started a couple weeks ago.
    Not running at all....I tried to move it yesterday (was at my office parking lot), tried to get him home.
    But he just would not stay running.
    I was doing 50MPH on the Hwy....the engine shut off...so I had to put it in neutral and start the truck while cruising....

    It gets worse when it is warm....to the point it will not turn over.

    RATRODKING Rockstar 100 Posts

    it sounds like your trouble is different than mine, since mine was running perfect, but would not start, but turned over like normal.
    did you see if you were getting good spark ? take a plug wire off and slide a screw drive in the end, then put the metal shaft of the screw driver near an engine bolt, have someone turn it over and see if you have good spark. make sure you are holding the hard plastic end of the screw driver while doing this or you will get shocked, if its getting spark.

    ok, just got done messing with my truck. started up 5 times perfectly. so i got my receipt and decided to exchange my fuel pump relay out for the heck of it. im just guessing at this point. and it still is starting normal. so i will see how it goes later today when i do some running around, and how it works going to work this week.
    cant really fix something if its working....... i like my 57 chevy 3100 truck... nice and easy to diagnose.

  6. MightyMax

    MightyMax Rockstar 100 Posts

    Well mine would does fine when cold, some "loping", but when it gets warm, that is when it just will not stay cranked.

    I just picked up a Fuel Pump Relay, so I am gonna put him, and see what happens.

    RATRODKING Rockstar 100 Posts

    cool ma, let me know how it goes..
  8. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Sounds to me that your relay is overheating.. Indicative of a bad relay. I would try that to be honest...

    RATRODKING Rockstar 100 Posts

    thanks murdog94.
    i did replace it today. got it new a year ago from autozone, so not sure of the quality. it was under warranty so thats why i decided to replace it.
    so im assuming it could work sometimes and not other huh ?

    what about the fuel pressure regulator ? where is that located and how does that work ?

  10. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    OK the Relay gets warm when running and cools off on the 2 or 3 hour time period... Hence why it wouldnt restart after a short time, and would after a couple of hours.
    Next the Fuel Pressure regulator is on the Throttle body itself, and it uses a spring and a diaphram to control the pressure from the fuel pump to the injectors. If it isnt leaking and the motor is running then on our style of motor there really isnt anything wrong with it.

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