We installed a used Holley Black fuel pump a few weeks ago on my truck. I bought a re-build kit for it and replaced the gaskets, plunger, and spring. After replacing the stock lp (and fuel lines w/ 3/8" hose) w/ the Holley, we noticed that the fp was considerably lower than w/ the stock lp. We decided it was the spring, and stretched it out w/ our fingers. Some help w/ fp, but I was still not happy (10 psi at idle). We then put 2 small washers behind the spring to add some tension behind it and that raised the fp to 15 psi at idle. I decided that I could live w/ that (no lower than 12 psi at WOT).

Sometimes, in the morning, when I first fire'er up, my fp takes a minute or so to get to 12 psi at idle, then drops to 8 or so at cruise. Its been in the mid 50's here in the monring. After about 20 mins of driving, the fp goes back to normal. Then, sometimes my fp will idle at 18, and sometimes at 15 (truck warmed up).

Any ideas for the inconsistance?

 

The low pressure in the morning is probably from the grid heaters cycling on and off. My PE pump would go from 18 at idle to 8 at idle first thing in the morning and then after about 5-10 minutes, it would go back up. My blue does the same thing.

 

Check for the grounding of the pump and drive it through a relay- had the same problem, killed other pumps, because if you have too low voltage at the pump it won't pump correctly and it will also damage the motor.

AlpineRAM

 

He's got a 30 amp relay on it right now being triggered off the factory lift pump wire.

 

Where does he ground it? Can you measure voltage at the pump terminals when FP is low?
Another possible cause would be the plunger needing to be deburred.

AlpineRAM

 

We used the stock lift pump grounding wire. Same way mine is.