jspaeth
11-28-2010, 12:51 PM
Like the title says, my fuel pressure (which I observe via a digital FP gauge in the cabin) increases under boost up to 58 psi or so (about 14.5 psi of boost....since my baseline FP is 43.5 psi), but then flatlines at 58 psi.
Consequently, this means I am having to use more injector than I should for all manifold pressures above 14.5 psi of boost.
This weekend, I rewired the fuel pump directly to the battery.....this WAS successful in some sense.........after doing this, my fuel pressure went up about 4 psi (i.e. it was 47.5 psi when the manifold pressure was 0 psi boost, rather than 43.5, as previously).
Naturally, I thought that I had "solved the problem" (perhaps the voltage to the pump was limiting it's output before)....
SO I dialed the FP regulator back down to the appropriate point (43.5 psi at 0 psi of boost).
Went out for a drive, and STILL, the fuel pressure won't go above 58 psi....it doesn't DROP off, it just stays there, even when the manifold pressure increases.
Any ideas? PS this is a brand new walbro 255 lph HP pump (did the same thing before with my old walbro 255 HP pump).
1) FPR no good? Reasonably new (2 year old) Aeromotive FPR....reliable brand, should be able to easily regulate FP on this setup
2) Stock lines (hard lines to and from the fuel tank) are too restrictive?
3) Something else (I have recently replace the fuel filter, so I don't think that's the problem).
Please chime in ONLY if you have a legitimate idea why this may be happening.
CLIFFS NOTES:
Fuel Pressure increase 1:1 with boost, but won't go above 58 psi (at 14.5 psi of boost), where it flatlines at 58 psi even as boost increases.
Aeromotive FPR (reasonably new), new Z32 fuel filter, stock fuel lines/rail, 740 cc injectors, base fuel pressure is 43.5, NEW walbro 255 lph HP pump (same thing happened with old Walbro pump, too).
Consequently, this means I am having to use more injector than I should for all manifold pressures above 14.5 psi of boost.
This weekend, I rewired the fuel pump directly to the battery.....this WAS successful in some sense.........after doing this, my fuel pressure went up about 4 psi (i.e. it was 47.5 psi when the manifold pressure was 0 psi boost, rather than 43.5, as previously).
Naturally, I thought that I had "solved the problem" (perhaps the voltage to the pump was limiting it's output before)....
SO I dialed the FP regulator back down to the appropriate point (43.5 psi at 0 psi of boost).
Went out for a drive, and STILL, the fuel pressure won't go above 58 psi....it doesn't DROP off, it just stays there, even when the manifold pressure increases.
Any ideas? PS this is a brand new walbro 255 lph HP pump (did the same thing before with my old walbro 255 HP pump).
1) FPR no good? Reasonably new (2 year old) Aeromotive FPR....reliable brand, should be able to easily regulate FP on this setup
2) Stock lines (hard lines to and from the fuel tank) are too restrictive?
3) Something else (I have recently replace the fuel filter, so I don't think that's the problem).
Please chime in ONLY if you have a legitimate idea why this may be happening.
CLIFFS NOTES:
Fuel Pressure increase 1:1 with boost, but won't go above 58 psi (at 14.5 psi of boost), where it flatlines at 58 psi even as boost increases.
Aeromotive FPR (reasonably new), new Z32 fuel filter, stock fuel lines/rail, 740 cc injectors, base fuel pressure is 43.5, NEW walbro 255 lph HP pump (same thing happened with old Walbro pump, too).