Question about 1999 GMC Suburban
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!
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
Sounds like one or more bad valve seats or maybe springs
Posted on Mar 01, 2009
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