starts fine then warms up, then no start

my son has a 1989 s10 pk/up 4cly, car starts fine at first runs great you go to the store come out truck does'nt start, i have change the starter first because from trying to start burnt up, i have changed the wires, cap, rotor,plugs, i even change fuel pressure reg truck is getting plenty of fuel. again in the morning or at any time truck starts right up when cold as soon as it gets hot and you have a delay of 20 mins come out try to start just cranks over :banghead: please help with any info thankyou

Pull the module in the distributor and take it to Advance Auto or Auto Zone they will test them free. I would use and use a hair dryer to heat it up before testing as it only does it when hot.
The pickup in the distributor will also cause this type of problem. I've used a analog ohm meter on both connections when unplugged. The dial should sweep when cranking.
A loose ground wire will also cause this type of problem.
OEM parts of this type last longer.

does this have a fuel pump in the gas tank?

never said if it was fuel injected or not, but because if it is FI, replace the fuel pump relay and see how that goes.

my 2000 s10 blazer did this crap about 3 weeks ago. sat there at an idle, shut the engine off, went to start it again and no sound from the fuel pump.would not start just sat there turning over. went back the next day with a new fuel pump relay but before i put it in, well, wouldnt you know, the damn thing fired right up. said screw that and shut it down, put in the new fuel pump relay and havent had a problem since.

and also, this is not just a chevy thing, ALL FI ENGINES DO THIS. dont just automatically think its a fuel pump, those are made to last the lifetime of the vehicle. replace the fuel pump relay first, my ford did the same thing.

While I have changed fuel pump relays I've found a lot more bad modules and pickups.