My daughter and son-in-law have a 1992 GMC 4X4 P/U with a 350 c.i. engine. Recently while driving the engine just quit. We determined that the fuel pump had taken the big one. So, my S.I.L. got a new fuel pump, pump sock and a new fuel filter and replaced them all. Once he was done, it started up again. Then next morning on the way to work, he got about 2 miles and it quit again and wouldn’t restart. They had it towed home.
Anyway, he has been fiddling around with it, trying to figure out what the problem is. Now, it will start and run for about 5 minutes then it quits again and won’t restart. He was convinced that the injectors in the throttle body were both bad. But it seems to me that if the injectors were bad, it wouldn’t start at all. I am certainly not much of a mechanic, but I am leaning towards it being an ignition module problem, since the engine dies after the module gets warm. But I really hesitate to suggest that he go buy something he doesn’t need.
You can test your theory several ways.
Once the car conks out, if you spray a little starting fluid into the air intake and try to start the engine, it shouldn’t try to start if it’s an ignition problem. If it does “catch,” than it’s probably a fuel issue. You can also use a timing light to see if you are getting spark.
It does try to start using starting fluid, but somewhere along the line I got the idea that the injectors get their pulse signal from the ignition module. I could be wrong about that though.
Well, there’s an “engine control module” (computer) that controls pretty much everything, but those don’t usually fail in the way you’ve described. Ignition modules do fail that way (my Mustang had this problem several times), but if it starts with the starting fluid, you have a fuel problem. Check for down-stream fuel filters. You might want to see if you can find someone who has a fuel pressure gauge - that would give you a whole lot of useful information.
Injectors? Possible, but that for sure is not the first place I would look, or the first thing I would replace.
If it were my truck, I would start and let it run until it dies.
Then check for spark, and if the fuel pump runs while cranking.
Three possibilities exist No spark or fuel pump. Suspect the RPM sensor (pump only runs while engine is turning, spark is only generated while the engine is turning. So if the engine is turning and the ECM doesn’t know it…) Spark is OK, fuel pump is not running. Look at the fuel pump relay. No spark, but the fuel pump runs. Look at the secondary ignition system, items like the coil, cap and rotor.
Is the check engine light on while it is running? Here how to read fault codes on that system.