My lift pump went out this past weekend, after running on a loaner, I picked up a new pusher setup. Everything went fine for the install. Upon priming, fuel pressure wouldn't go above 4 psi. until I started it. Ran fine and pressure eventually went up to between 10 and 12. My question, why would pressure be lower with brand new pusher than old stocker? Fuel lines are now 3/8 i.d. from pusher to VP. No leaks, pump runs constantly. Everything seems good except for the lower pressure. Is this a result of larger lines? I revved it up to 2k and pressure dropped to a solid 10, sitting in driveway. Any ideas??

 

Larger lines could cause this. If your pressure never drops below 10psi even at WOT, you will be fine. I have a brand new pump and mine at idle hovers between 13-14 and drops to about 9-10 at wot.

 

The reason your fuel pressure is low is because your pump is not putting out the volume. The reason the pressure drops any amount is because the pump cannot supply the volume.<br>This has nothing to do with the lines, once the lines are filled with fuel. It does not matter what size your lines are in this case. They could be 4&quot; in diameter and you would not have a pressure drop if the pump could supply enough fuel to the injector pump, the &quot;restiction&quot; at the end of the line.<br><br>Now, you could look at this another way. The restrictive stock fuel lines were small enough that the stock pump, however low volume it is, was able to maintain X pressure, because the lines were restrictive. This was actually detrimental to the injector pump because the lines were causing the pressure resistance and did not allow enough fuel to the pump. Now that you have opened up the fuel lines the only restriction in the system is the pump, which has a return line coming off of it, and with the current fuel pump you have, it can only supply the volume to maintain 10 psi of pressire when the engine is running at 2K RPMs, including the return fuel.<br>My Holley Blue only pumps at 11.5 PSI, idling, and drops to 8 at WOT. As I bomb some more I will probably have to switch it out for a Performance Engineering PE4200, which can supply enough fuel to maintain 16 PSI under WOT with Super Mentals.<br><br>Chris