I am running the stock intank TBI fuel pump to a Mallory 3 Port Return regulator to a Holley 750 Carb. Here is the problem, when I first turn the key on the fuel pump primes fine. After starting the car though I don't get any fuel pressure. Carb runs out of fuel and car dies. Turn key fuel pump primes fine. While trying do diagnose this, I hooked up another fuel pressure gauge and still showed no fuel pressure. Then all of a sudden got fuel pressure on gauge and ran fine. Turned off car, let it sit for a while, now I do not have fuel pressure again. Any ideas on this? Could it be the oil pressure sensor?

 

Sounds likely.

 

I fixed the problem. It appeared that the Fuel Pressure Relay wasn't working. I tested it by running a hot lead from the battery and spliced it into the Tan/White wire on the Fuel Pressure Relay. As soon as I did this the fuel pump kicked on and the car started and ran fine. I then found a switched ignition source to tap into the Tan and White wire instead of going direct to the battery.

 

The fuel pump relay doesn't work without a functioning ECM in the car.