Question about 1999 GMC Suburban

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'99 Suburban 7.4L Random starting problem

My '99 GMC Suburban K2500 w/7.4L has 95K miles on it and has been well maintained. On a cold Montana morning (below zero even) it starts perfectly on the very first crank. It does this any time it's been sitting for a long (8+ hours) period of time. However, if I drive somewhere and park for say 1-6 hours it will crank for a very long time before starting (about 10-15 seconds). When it does start it stumbles a bit as if I had run out of fuel and it's finally reaching the engine. If I park and run in somewhere briefly and right back out it'll start perfectly. I thought it was a fuel problem at first and still would if it weren't for the perfect starting after sitting for a period of time. Anyway, I replaced the cap, rotor, coil, checked plugs and wires, replaced crank sensor, fuel filter, air filter, and finally ended up replacing the fuel pump after none of the other steps helped. The pump was louder than I thought it should be (the hum was steady but loud enough to easily hear even over the running engine sound). The pressure checked out at the lower end of the acceptable range. I have tried cycling the pump multiple times before starting and that doesn't seem to help at all. I also tried removing the gas cap thinking vapor lock may be the problem? I also ran a 2 guage welding cable from the engine grounding directly to the battery negative terminal. Checked connections at all ends of both battery cables, cleaned contacts and even put in a new Optima battery. So, I've got a brand new fuel pump and all kinds of other parts but my problem is still there... Any ideas? The only thing left I can think of is the PCM but I'd feel like an idiot if there's something simple I'm not thinking of. I'm a relatively novice mechanic but have all the tools I could need and am willing to try and learn anything. Please help!

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  • jake406 Feb 25, 2009

    Thanks for the response. I changed the crank sensor already (one of the first things I tried). Checked all wires/cables for corrosion and tightness. Also replaced coil, cap and rotor and I do have spark. Checked distributor tightness while changing cap/rotor and it's nice and tight. No check engine light, no codes in history. I do have a good Snap-On scanner (even though I'm still learning how to use it).

  • OHayabusa Apr 04, 2009

    Same truck/thing@204k miles. Curious about solution.

  • athomson Apr 06, 2009

    I have a similar problem. Cold start: Starts right away most of the time. Every 1 to 4 weeks, cold start will back fire and then be hard to start. Once started, it will shake/vibrate violently and then smooth out after a minute or 2.

    Warm starts consistently are hard starts. Requires long cranking to get the engine started.

    1999 7.4 liter GMC Suburban K2500, 160,000 miles

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Have you looked into the ignition module? that sounds like the problem.

Posted on Mar 28, 2009

  • heyheyhey1 Nov 27, 2010

    Try the fuel pressure regulator. Mine was leaking raw gas through the regulator directly into the intake manifold. Acted like a vapor lock/flooded engine.

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Hi!!!! try to change the crank sensor .. but before you change it . check the ignicion coil, all wires ground and positve . star from the battery.make sure they are tigth.in place move one by one to ccheck in case it just holding by o0ne tiny piece o loos. than. set up for ignition timing check the ignition rotor is in place the distribuitor in place and tigth.(check the ignition control module is on the bottom of the ign rotor).get somebody to help you crank the car until theignition rotor points to the piston .no. 1 .after you do all this put everthing back star rhe car unplug the wire from the spark plug no.1 se if you have spark.. you have engine ligth on???

Posted on Feb 25, 2009

  • delgadostat Feb 25, 2009

    take of the starter and chek the teeth on both starter and flywhel. if somebody o you change the fuel filter check if the arrow points to therigth dirrecion. o take of and blow from one side if is cloge replca it..

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  • 14 Answers

Sounds like one or more bad valve seats or maybe springs

Posted on Mar 01, 2009

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