GM-GMC: truck wont start after it has warmed up, gm crate motor, starter solenoid

Question
I have a 94 Chevy Z71, 350, automatic, the truck has never failed to start when cold, but after running it, and turning it off it won't start until it sets for up to 1 hour depending on outside temp. It has 180000 miles but the engine has less than 10000 ( new GM crate motor ) It has done this with the old motor and now the new motor. I replaced the starter thinking it was the problem, no luck. It doesn't even hesitate to start when cold,  but after warming up the starter doesn't engage, the battery doesn't drag there is no clicking like it is trying to, the lights will come on , stero etc. When it does start again there is no hesitation at all, fires right up. There is times however i can drive it all day, and it will start back up. I going to replace the coil, but not sure if thats it, do you have any other suggestions that might help ?    thanks

Answer
You have either a bad connection (loose, corroded, etc.) at the battery or starter, or, a starter solenoid that is bad.

The coil has nothing to do with an engine that will not turn over (crank) when the key is turned to the "start" position.

You stated that you changed the starter.  Did you change the solenoid, which is mounted on top of it?

You can have the starter tested for free at most auto parts stores, but the test will not be performed with the starter hot (as it is when it is on the engine after you shut it off) and the test may not indicate anything wrong.

Chech all your connections between the battery and starter for looseness and/or corrosion.  Battery cables sometimes corrode under their insulation.