'90 vette no injector signal when hot

Engine starts and runs fine until after initial warm-up. If shut off, then there is no injector signal at restart. Always have about 36lbs. of pressure and ignition. Checked grounds. Engine runs fine regardless of engine temp, just no fuel signal at restart. Always voltage at harness. Sounds like no ground signal out of ecm, but don't want to make a costly mistake. After lengthy cool down, or overnight, starts and runs fine, until attempted restart. No codes stored. Doesn't seem to be a vats problem, because symptoms are consistent with temp. Same for bad ground possibilities. Voltage runs about 13.6 consistently. Any Ideas?

Check with a test light +Battery to one of the injector grounds to the ECM at the injector harness. If the test light doesn't flash while cranking, check the ICM reference output by backprobing, I think purple/white, for cycling output. I think there's a 3-wire connector to the icm you can check this at. I would need to have a wire diagram or a diagnostic chart to make this clearer. Basically, if you're not getting injector cycling when hot then the problem is probably in the circuit from the ICM or the ICM itself.