Has 64,000 miles. Truck would not start for the longest time. I changed sparkplugs, starter and new fuel filter. I could hear humming from fuel pump in gas tank so I assume it to be ok. Finally decided to check oil dipstick. It had an odor of gasoline in it. I changed oil, too the fuel pump relay out and disconnected fusible link from the firewall. Cranked the engine several time, plug back in the removed items and it started right up. All appeared normal. Next day went out to start, crank was normal and would not start. Check the oil dipstick and it has that gas odor. What can be wrong. Also "Service Engine Soon" light has been on for the longest time. Live on and Island in Alaska, have not testers of any kind. Will accept assumptions and than check them out.
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It might be your distributor. You seem to be getting fuel, so I would now focus on spark. I don't know about the gas smell in the oil...that may be from turning the motor over repeatedly without ignition. I'm certainly no mechanic, so that is my best suggestion. Good luck to you.

 

most likely,a fuel pump...they run,but low pressure and won't start

 

Hello,

I just signed up to this forum after reading the problem you are having. I have the same kind of truck. 77 GMC C3500 1 Ton Dually. From what it sounds like is that you might have a problems with your head gasket, or carb dumbing to much fuel in the cylinders and the rings could be bad which allows the fuel to pass and go into you oil pan. I have a gear for the speedometer cable. I know it would have to go into the tranny but not to for sure how to get the old one out and new in.

Jeff

 

One day early in morning my gmc sierra will not start then i decided to check oil stick, it had an gasoline in it, i changed oil, too the fuel pump relay out and disconnected fusible link from the firewall. Cranked the engine, plug back in the removed items and it started right up. Next day went out to start, crank was normal and would not start. Check the oil stick and it has that gas odor. What can be wrong. Also service engine light has been on for the longest time. Will accept assumptions and than check them out.