My friend and I have started a 5.3 liter swap into a 1989 nissan 240sx. We have the motor and trans installed. We sent the computer off to Hawk's Third Gen and had the VATS deleted so that wouldn't be an issue with the build. The 5.3 has a ls1 intake on it and we replaced the returnless style fuel rails with return style rails. Before we went to a return style system the pump was building 80psi, and we had to regulate it down to around 58psi. The problem that we are having now is that the car will start and run for a moment and then it will fall on its face and die. Also since we went to the return style system the car won't build fuel pressure, its like it is return fuel to the tank as fast as it is pumped and we can't get the regulator to adjust and build pressure. The only way to get the pressure to build is to almost completely clamp off the return fuel line. And even then with about 60psi of fuel pressure the car will start and run for a few seconds and it will die. The only way to keep the car running is to spray ether into the intake. Is this just a fuel pressure problem or could this be related to VATS shutting off fuel? There were no VATS related codes shown when we scanned the car.
Also the car doesn't have o2 sensors hooked up yet but that shouldn't keep it from idling.

 

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Sounds like you have the lines hooked up backward. The fuel pressure regulator on the fuel rail will be hooked to the tank RETURN line. If the pump supply is hooked to the regulator there is no way for the fuel pressure to build in the rail.

 

We have the regulator hooked up on the return line and it still won't regulate pressure up or down. And unless we clamp off the return line it just reads 0 psi.

 

Sounds like the regulator is bad.

 

That's a possibility I guess but I don't see how it could be because we just bought it brand new. But I'm gonna check it and make sure it's working

 

Do you know that the gauge is accurate?

Andrew