hot weather non starts

i have a 95 4.3 vortec 250K miles my problem seems as when the outside temp gets above 80 degrees and i shut off engine it refuses to restart until the engine cools down.....have replaced thermostat 195 degree, cleaned injectors replaced fuel filters and ignition module
any ideas?

this is a ps...when eng quits won't crank or anything

Look at this web site and it'll probably help explain your problem and how to fix it.
Although problems don't usually start with the temp as cold as 80
http://www.streetrodstuff.com/Articles/Electrical/Hot_Start_Problems/