Failure to crank...sometimes

[cpjonesman]

1988 K1500, 4x4, 5.7 V-8, 162,000+ miles: A few months back, I had a complete failure to start. After diagnosing no fuel at throttle body, I replaced the fuel pump and starting was no problem. After a few weeks I had problems starting. I used a starting fluid and it would crank and eventually ran ok. I replaced the fuel pump relay. Even though I was getting an oil pressure reading while cranking, it looked a little sluggish so I replaced the oil pressure switch as well. All was well until I left work a few nights ago and I had trouble starting. At first it would not hit, I sprayed starting fluid into the throttle body and it hit momentarily and eventually cranked and ran. Last night, I cranked up to leave work and was about two miles down the road and it died. After a couple of tries, out of frustation I pounded the dash a couple of times (my inner child I guess, being on the side of the road at 03:00 AM & an hour away from home). I tried again and it cranked and brought me home. I read in another thread that someone had an ingition switch/connection problem on a '95 doing something similiar. I have had an occasional issue with the radio and fan/air/heater electrical controls not responding right away. Anyone with any suggestions??

[Crasen]

If you can get the truck running when this is happening with starting fluid I would assume you are getting spark, but I would check it just the same, I would also try to get a noid light to keep in the glove box so you can see if you are getting an injector pulse when it will not start. You can unplug the electrical connector and plug the noid light in the connector and try to start the truck. If there is an injector pulse the light should star flashing when the engine in cranked. You could also hook a fuel pressure gauge up to it and just leave it there so you can look at it easily when it won't start. There should be about 9-14psi at the throttle body. You could also try changing the fuel filter. The problem could very well be an ignition switch.