97 Suburban K1500 5.7 won't start, but turns over fine,has spark and is getting fuel.

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by boycbronco, Dec 29, 2010.

  1. boycbronco

    boycbronco New Member

    Hello, new here but looking to contribute and gain information.

    I have a '97 Suburban with the 5.7 Vortec, approx. 230K miles and (has been) still running very strong. About a year ago, it began to start a little hard, particularly if it had been sitting a few days. In other words, it turned over just fine, but would not fire until several attempts had been made. I had already replaced the fuel pump in it shortly after I bought it (about 160K miles). I changed the plugs and fuel filter, and the problem seemed to go away. A couple of months ago, the problem returned, and got worse until it would not start this week. I should also mention that no loss of power has been noticed. Here's what else I have tried:

    1) I thought it might be a fuel problem, particularly because it sits a lot and the tank is rarely full. So, I ran a bottle of fuel system cleaner through it (one designed for large vehicles with 35+ gallon tanks) and completely filled the tank. No real change noticed. Shortly after this is when it quit firing altogether.
    2) Checked spark, checked out good. I did notice, however, that a couple of wires had rubbed through each other a bit and were arcing. Replaced wires with a brand new set.
    3) Took readings on coil with ohmmeter. Results were somewhat inconclusive but seemed to be okay. Went ahead and put in a brand new coil, anyhow.
    4) Changed fuel filter (again), even though I changed it less than 6 months ago. Verified that I am getting fuel at the engine with my fuel injector pressure gauge and relief valve.
    5) Put in a brand new distributor cap and rotor.

    After all this, it still turns over just fine but will not fire. One person suggested to me that maybe the timing chain jumped, but this does not make sense to me, since the symptoms have been present for some time, yet the engine ran like a top and started easily once the engine was warm. With a timing chain issue, I would expect (at minimum) a rough idle, missing, or a bent valve(s). The onboard computer is not throwing any codes.
  2. stephan

    stephan Rockstar 4 Years 5000 Posts

    Welcome to the club BB. It's not the timing chain jumped cuz this problem comes & goes & a timing chain jumped would leave your valve timing off, all the time.
    Since you seem to have checked or replaced most everything along the way, it sounds like it might be fuel pressure bleed down, or just not generating enough fuel pressure initially for start up, after sitting for a few days.
  3. MrShorty

    MrShorty Epic Member 5+ Years 1000 Posts

    I was thinking along the same lines as Stephan. I would put a fuel pressure gauge on it and see how long it takes for the system to build up pressure on cold starts.
  4. boycbronco

    boycbronco New Member

    Thanks for the quick replies, gents. I do have fuel pressure and it seemed to come on fairly quickly. How much pressure should I have?

    What are the chances it is the fuel pressure regulator? Is this a common fail? I had a similar issue on my Nissan sedan last year, though it is a different design with the regulator incorporated into the fuel rail.
    Last edited: Dec 30, 2010
  5. MrShorty

    MrShorty Epic Member 5+ Years 1000 Posts

    I haven't tested it out myself, but the overall concensus I see seems to be 50+ psi. Anything below 50 is often associated with problems.

    Hard cold starts usually aren't a regulator issue. The regulator is a basic, mechanical back pressure regulator (your Nissan could very well be the same basic design), and there are really only three scenarios to look for:

    1) Regulator opens too early, causing the pressure to be too low.
    2) Regulator doesn't open, or opens too late, causing pressure to be too high.
    3) Diaphragm in the regulator ruptures, leaking unmetered fuel into the intake. This is usually most evident on warm starts rather than cold starts, because the excess fuel "floods" the engine. After sufficient time has passed, the excess fuel dissipates, which usually means normal cold starts.

    You don't say how you are measuring the pressure, but, if the pressure (a) comes up to ~60 psi immediately, and (b) stays at 60 psi while cranking, and (c) the engine doesn't start, that suggests to me that it is not a fuel issue.
  6. Looey

    Looey Rockstar

    1. Oil pressure switch.
    2. Fuel pump relay.
  7. boycbronco

    boycbronco New Member

    I forgot to come back to let you all know that the problem was indeed the fuel pump. I was only getting around 50 psi. I also replaced the wiring harness in the tank, as it was suggested the harness could ultimately be the reason for the pump failure.
  8. BobEhud

    BobEhud Rockstar

    I do this for a living and have replaced more GM pumps than i can count.Pretend like your 1/4 tank mark is empty and you will never have to do another GM pump.The baffling in these tanks are awful and the reason the wires burn going to the pump is the pump sucks air if the tanks low ruining the vane style pump GM uses the gas is a lubricant to these pumps.Our shops do a few every week.
  9. greatdane

    greatdane New Member

    two thumbs up, good info thread, thanks guys.

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