intermittent starting problems

I am working on a 1995 S10 Blazer. it has a 4.3l vortex. The vehicle runs good. The problem is when it is shut off at end of day. Then the next morning it will not start. Then at a different time in the same morning it will start and run all day. I have fiddled with it when it will not start. It acts like it wants to fire but will not start. If I am persistent with it and crank and pump the hell out of it eventually it will start. I have checked the fuel pressure when it will not start and it is good. There is also spark. I don't know what to check next. I has been cold when it does this. Any ideas what to look at?

Next time. Try some starting fluid. If it fires up, fuel delivery issue. if not, suspect ignition.

check the ignition module/coil? if it has a crack & gets moisture it it they become weak... weak spark. next bet is to check the compression on all cylinders.. cold should be around 90-100PSI. another possible may be a bad ground strap from the block to the battery/body. have you checked the CPS? a bad Cps will allow a vehicle to run, but when it gets hot it will refuse to run correctly with differing information coming from the CPS & camshaft sensor. there are voltmeter tests out there to run on these..