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Truck will not start ~ 1997 GMC with 5.7

Discussion in 'General Chevy & GM Tech Questions' started by neckdown, Dec 22, 2012.

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  1. neckdown

    neckdown New Member

    I have a 97 GMC 4x2 with a 5.7, it cranks over and at times it seems like it is going to start but wont. When I let off the key it bumps several times, also while trying to start it it will backfire sometimes. I have replaced the crank sensor, coil and had the icm tested several times and it is good. Any help would be greatly appreciated. Thanks.
  2. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    Is fuel getting to the motor? If fuel is, is it at the right pressure? Many things can cause the truck not to start, especially a truck like your which as so many sensors that need to communicate to allow it to start.

    When did this start happening? Was is random or did you replace something and it started acting weird.

    I once brought my truck to a shop after having trouble with a repair, during my work I unplugged the crank shaft sensor, when the shop had finished their work they couldn't get my truck to start and were so confused. They forgot to plug the crank sensor back in... That how easily a starting issue can be caused.
  3. neckdown

    neckdown New Member

    It started a couple weeks ago out of the blue. If the truck sat a couple days it was hard to start. Fuel is getting to engine but I dont have a gauge. Tried starting fluid with no results, just keeps turning over.
  4. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    Do you have spark to all the cylinders?
  5. neckdown

    neckdown New Member

    Didn't check all cylinders but had spark at two of them, will check rest today. Changed cap, rotor , wires and plugs about a year ago with aftermarket parts.
  6. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    There may lay the problem, GM trucks really are built to use AC Delco plugs and usually don't like other plugs. The same goes for wires. Caps and rotors can be after market, but only some brands make ones that are high enough quality.
    Heres a simple list of how plugs should be bought.
    Delco: GM vehicles
    Campian: Dodge
    Motorcraft: Ford
    Bosch: Imports
  7. neckdown

    neckdown New Member

    OK. Will try changing them out, hopefully a cheap fix.....Thanks. Will post later any results or if I pulled out what hair I have left
  8. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    Btw, Before you go buying parts, is the truck throwing any codes?
  9. MrShorty

    MrShorty Epic Member Staff Member 5+ Years 1000 Posts

    How did you check this without a pressure gauge? These engines seem to need at least 50 psi (and 60 is better) to start, and there are many cases described where the fuel pump was only generating 40 psi. I'm sure there are ways to check for fuel without a pressure gauge, but it seems like they would always leave the question of sufficient pressure.

    x2. Many no starts will leave clues in the computer if you ask the computer if it sees a problem.
  10. neckdown

    neckdown New Member

    OK, truck not showing any codes, changed plugs and it started . Thanks for the help I do appreciate it. Have a great Christmas and New Year.

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