Question about 1993 Chevrolet C3500
I have a 1998 chevy silverado 7.4L. The engine has about 155k on it. I changed the fuel pump with an ac delco one, along with a filter and an injector cleaning. The truck will start fine about half the time the other half it will crank for 30 or so seconds before firing. It seems to start when i let off the ignition switch. Also seems to start a little bit better when i give it throttle. I checked the compression in the cylynders and all are above 160psi and within 10% of each other. I replaced the distributer about 2 years ago, but the problem still exists.
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Try to have the fuel pressure checked. It should be around 50-60psi. If your fuel pressure is within spec, start checking your throttle positioning sensor, advance, coils, and distributor. It wouldn't hurt to pull a plug and hold it on or very close to the block and have someone bump the starteer to see if it is getting good fire. I would assume it does as it still starts and I assume runs fine. I think I would bet on the advance, it should be a vacum advance but I am not sure. When you first start a car it will run rich, fuel injection runs 14 to 1 or 14 something, but to start needs to be a little richer, the timing will also advance so it will run smooth on inital start up. If your fuel air is a little rich as it should be but your timing is not being advanced that could very well be your problem.
Also try to leave the key in the pre-ignition position for around 5 seconds before you start the truck. See if that makes a difference. If it does, the culprit is definitely the fuel pressure.
I hope this helps. Thanks and good day.
Posted on Feb 13, 2010
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Posted on Jan 02, 2017
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