I just got done putting in some new Bosch design III's from FIC along with a holley adjustable fuel pressure regulator. All seemed to go fine, but before i put the runners on i pressurized the system to check for leaks with a FP gauge on. The pressure went to around 40 PSI for the couple seconds the fuel pump runs when the key gets turned on but as soon as it stopped the pressure went to 0 after a couple seconds. Shouldn't the system hold pressure for awhile?

Mine isn't holding all that well either. Once the pump shuts off it starts bleeding down til it gets to about 20psi then it slows way down. Mine is probably leaking back at the pump thru the little hose. It's not an ideal situation, but as long as the pump can maintain pressure when the engine is under heavy load it should be fine.

I replaced my pump last spring and it held pressure fine, but I had forgot to install a compression type clamp. I suspect that now mine is leaking slightly because of it. I don't much relish the idea of taking it all back apart but I probably will so I can sleep better. I need to work on it anyway since the spectra filler neck doesn't line up right.

Did you prime the pump several times? Mine did this right after the install. I clamped the return line and saw that the pressure held. Removed the clamp, and then I let the pump run for about a minute ( 12v to Term G of the ALDL). Worked fine after that. Think maybe I just had to work some of the air out of the system.

The only "priming" i did was to turn the key off/on 3 or 4 times. I will clamp the return line and see what happens.

This is normal after an injector install. The fuel lines and injectors are full of air. The sole pupose of pressurizing the system is to check for fuel leaks, i.e. o-rings. If no leaks you should be good to go. Once you have everything buttoned up and crank it over the injectors will pulse / purge the air, once running you can monitor fuel pressure at the fuel rail.

Thanks ...