Ok so I have a lifted 95 k1500 that's been doing something.....odd. so right now I can go to my truck and turn the key and it'll turn over, no problem. I'll go about my errands for a couple hours, then I'll go to turn it on after it resting for, let's say 30 minutes.....it'll turn over but with some hesitation.....now here's where it gets weird, if I drive it for another hour or two and park it for another half hour it won't turn over at all. For at least a whole day....I'll go back the next day and it crank like nothing ever happened. I tested the battery and connections as well as the alternator, all where in the green. I swapped the battery anyways and redid a ground wire to the body. Still does the same thing. I had another mechanic look at it, I left it with him for the day, he drove it around used it as normal and nothing happened. So now it comes down to it basically has to be used constantly for more than two hours, then it'll start to happen. Also I've noticed that after all this happens and it won't turn over ...the voltage is at around 10 when it usually sits at 13 1/2 ish .....I tested the oil pressure sensor, crankshaft sensor as well as the vacuum hoses .......I'm at a complete loss here....some one help me

 

That's not enough to start with. Something is draining your battery.

 

I'll bet you need a new starter. Just to be clear, are you saying when it fails, the starter does not engauge/spin? Do you hear a click? Does your dash volt gauge drop and/or does your dome light dim when this happens? How old is your starter; how many miles on your truck?

 

Ok so the body has over 250k but the motor I rebuilt myself with all new gaskets and sensors. The alternator and starter are from the old set up so that's possible but when it's going through its issue it definitely tries to start and all lights on the dash and dome are on as well as the attempt to turn over from the starter.

 

Can do a voltage drop across the battery cables to verify they are good and check to see if you have sufficient power on the small wire on the starter when the truck is acting up.