1998 GMC Sonoma pickup intermittant hard to start


#1

The Sonoma is basically the same as a Chevy S-10. It has a 4.3L V-6, auto trans. and 148K miles.

About half the time it will crank and crank and crank before it finally starts. Other times it will start with the first cylinder to hit TDC. I have found that waiting with the key on until the security light goes out will SOMETIMES make a difference. If I don’t wait for the light to go out, it always takes several attempts to start. I hope that symptom is not entirely in my mind. I don’t think it will start at all if I just continue to grind on the starter. Doing it in 3-5 second bursts sometimes works, sometimes not. It does not seem to matter if it is the first start of the day, or after the engine is warmed up.

The fuel pump appears to have been replaced at some time as some idiot sawed a hole in the bed to do it rather than dropping the tank. There is no way to know how old the pump is, but I suspect they may have been fighting the same problem, and should be shot.


#2

I would do a diagnostic on the fuel pressure per post #4 below:

“The injection system needs between ~56 to 60 lbs at the fuel rail to start the engine. Then you need a little less to keep it running.
When you first turn the key to RUN (not start), the fuel pump relay turns on for ~4 seconds. The system is expected to have held at least ~35 lbs from the last time it ran. If you have a leak (fuel pressure regulator, fuel pump check valve, spider, injectors) the system may not be able to pump enough gas that quick to reach ~58 lbs. To test for this, you would watch the gauge after turning the engine off. Ideally it should hold pressure for at least a day.
A rapid drop would point away from the pump, but not the pumps check valve, FPR, Spider or injectors.”