thunder1road

My 1989 Camaro RS had a problem where it would run great for a while and then stall out on the road - as if it had run out of gas. The car would start if the TBI was primed with gas but wouldn't run on its own. Sometimes - after stalling - it would start the next day BUT it would never start right after a stall. Something was keeping the fuel pump from getting voltage. If i jumped 12V right to the fuel pump wiring above the rear axle - I could hear the pump running inside the tank. So - something in the system was blocking the ECM from giving the command to allow the fuel pump to run.
POSSIBLE CAUSES ARE:
Bad ECM
Bad Fuel Pump Relay
Bad wiring in car or on fuel pump/gas gauge apparatus in gas tank. (especially bad ground wire)
Bad ignition module in distributor - this module sends pulses to the ECM. If
the ECM does not see the pulses - it will not trigger the fuel pump.
Bad 3 wire oil pressure switch - if the ECM doesn't see oil pressure it will not allow the fuel pump to send gas to the engine (this may not be true for all Camaros with electric fuel pumps).

Schurkey

Popped fuel pump fuse (Let's start with the easy stuff first.)
Defective pickup coil in distributor--fails to provide signal to module (engine will not run even if you supply fuel)
Defective wire harness between distributor and ECM. ECM does not get "crankshaft turning" signal

I'm not aware of any of these vehicles where the ECM monitors oil pressure to control the fuel pump. The oil pressure switch bypasses the ECM/Fuel pump relay to power the pump directly.