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97 GMC Suburban sputters under load

Discussion in 'Performance & Fuel' started by CCRDad, Apr 12, 2013.

  1. CCRDad

    CCRDad New Member

    I have a 1997 GMC Suburban. There's been a problem with acceleration for about 6 months. Basically, truck start fine, no hesitation. Idles fine. Sitting in park and revving up the motor it sounds fine.
    When I'm going low speeds of 20-30 MPH the truck runs fine. but then when I try to accelerate, it sputters and cuts out (never dies) until I release the pedal and then it runs fine again.
    When I start the truck, the fuel pump has gotten louder, and now while its running the whining the fuel pump makes kind of goes up and down in pitch. I have replaced the fuel filter, newer plugs, wires, rotor. I took it to Autozone and hooked it up to the code reader and it says it's running lean on bank 1 and bank 2 (engine light is on). Truck has 168,000 miles.

    I think it might be the fuel pump, but I have also heard it could be the O2 sensors. I can't afford to replace everything right now so I was going to do the fuel pump myself this weekend but wanted to make sure that was the problem. Has anyone heard of this situation before?

    Thanks for any help!!
  2. MrShorty

    MrShorty Epic Member Staff Member 5+ Years 1000 Posts

    I was going to suggest a fuel delivery issue. If you don't want to "guess and check" on the fuel pump, borrow the fuel pressure tester kit (I think Autozone lends it out) and see what the fuel system is doing before going to the expense of replacing the pump.
  3. CCRDad

    CCRDad New Member

    Ok thanks! Do you happen to know what I'm looking for during the test? I've never done one of these before.
  4. MrShorty

    MrShorty Epic Member Staff Member 5+ Years 1000 Posts

    Any good manual should describe a fuel pressure test. Basically:

    1) before starting the engine you are looking for a pressure of 60-66 psi
    2) A slight drop after starting the engine, but it should not drop below 50-55.
    3) When you rev the engine or otherwise under load, the pressure should remain high (in your case, your symptoms could be caused by the system pressure dropping off under load).
    4) When the engine shuts off, the system should remain pressurized.
  5. CCRDad

    CCRDad New Member


    Ok, I will check it out, Thanks!
  6. CCRDad

    CCRDad New Member

    Ok, looks like it was the fuel pump. A friend and I dropped the tank yesterday and replaced the fuel pump and no more problems! I didn't get a chance to test the pressure before we replaced it, the auto parts store would only sell me the tester, wouldn't let me borrow it.

    But the pump sounded so bad while it was running we took a chance. It was also missing the filter screen at the bottom of the pump that was installed (looks like it has been replaced before), so when I put in the new pump, I added a filter screen also.

    Didn't take us long either, a fairly simple process. Had it done in a little over an hour. So the pump was $90 and the screen was $7 and a 12 pack for Jim, $10. Well worth it!

    Thanks for the replies back!

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