Hello guys, just replaced my fuel pump but a new problem appeared.

After engine reaches operating temp, it will begin to drop RPM @ idle, stumble and in a few moments will stall (will not start back until cools down).
before reaching op.temp, it runs perfectly.

When it fails to start, I did a test at ign.coil and fuel injectors harnesses; they are NOT receiving power (could be not receiving +12v from ASD relay, or not receiving ground from PCM?...)

also, fuel pressure seens fine (by pressing schrader valve); but will get a gauge to test it correctly.

Any tips on what's causing this? I thought about the crankshaft pos.sensor, but would it fail only when hot? and also could it cause the stumbling (like running out of gas)?

Thanks!

ps. and also check engine is NOT lighting up!