1996 Chevy Camaro engine cranks but will not start (intermi

The engine will crank fine but sometimes will not start.This is a intermitant problem and happens when the outside temp. drops below 40 degrees F.The fuel psi is 50 when key is on and engine is not running, if engine does start the fuel psi is 42, We have replaced the fuel filter. The ignition coils are providing spart to the spark plug wires. With the key ignition on the fuel pump delivers fuel until the 50psi is reached then stops pumping the engine will start. if the key is turned on and the fuel pump runs but never turns off and continues to run (producing 50psi) the engine will not start.In both cases the fuel psi is 50 psi without the engine running.There are no fault codes or check engine lights on. I was told the ignition key electrnic chip could be defective and could cause this problem, so we replaced the ignition key but this contition still happens. We have had it to our local repair facility and brout it to the chevy dealership service dept. but they could not find the problem.Please let me know what we should do next. Thank You, Ken Beer