[olddog]

I have an aftermarket EFI system that uses a Ford EEC4 control unit from a 1989-1993 mustang gt. It has a Mallory adjustable fuel pressure regulator and is a return type fuel system. The regulator has vacuum connection that raises or lowers fuel pressure 1:1 with manifold vacuum/pressure. Engine has 36 lb/hr injectors in it. I believe they are Ford injectors.

With the vacuum line disconnected engine running, what should the fuel pressure be set at? I believe this is a correct way to set the pressure.

The fuel pump only runs for a few seconds, when the key is turned on, so the engine off fuel pump running test does not work for me. I tried this and then got much higher pressure when I started it. I may have something bleeding pressure off, but not sure yet. Sometimes it holds and sometimes not. I'm suspecting injectors are not always shutting off tight, but the fuel pressure too low may cause this to happen.