View Full Version : LS1 fuel pressure problem

10-07-2006, 07:27 PM

In 2005 (all that year, it seems!) I upgraded my car.....intake, Injectors (30 lb Ford SVO), valvetrain, under/overdrive pulleys, TR224 cam, Racetronix fuel system with wiring harness, blueprinted oil pump, Shaner TB, wire mod, etc. etc.... I have a electronic fuel pressure gauge on the A-pillar and had the computer tuned for my combination. The car sat for most of 2005 as I put on upgrades. I expected the upgraded fuel system to solve a fuel pressure drop problem I was seeing at WOT. My fuel pressure before the Racetronix system was ~56 to 58 psi according to the pillar gauge and dropped to the low/mid 50's under WOT. After all my upgrades I was getting -60 to 62 psi pressure with a WOT drop to about 56 to 58 psi. Most of my driving is daily driver style with some spirited bursts of speed.
But recently during some of my driving when I crack open the throttle I am seeing a pretty severe drop in fuel pressure to the low 50's and even lower and it does not seem to recover until I let up on the throttle. My sprints are not to long as it is local road/highway driving.
I checked the fuse in the wiring harness and the connections at the relay. The wiring harness is connected to my alternator. All looks normal. Pressure at idle is normal but goes down a tad under power.
What else may be happening? What else should I check? Replace the fuel filter? :confused:

Thanks for all input !!!


10-07-2006, 07:28 PM
DrkPhx wrote - Check the fuel pressure at the rail with a mechanical gauge for an accurate reading. The electronic gauge relies on voltage. Have you logged your injector duty cycles before and after?

I can put a mechanical gauge on and rev the engine....this should help narrow things down a bit.....I guess I did not think about the electric gauge having a problem....hmmmm....I'm not too good with electric there a way to check why there might be a voltage drop under acceleration...but I do not see other systems affected like lights or panel lights or the other guages (electric oil temp and water temp).

I have EASE...can I check duty cycle with it? I have been pretty much out of serious car tweaks since I got her back on the road and I do not remember much about my software anymore. Time to re-learn!

10-08-2006, 08:36 AM
Whats the most varriation in pressure you should see? mine gos from 60-48 at times while cruising around under light load.

10-10-2006, 08:40 PM
Whats the most varriation in pressure you should see? mine gos from 60-48 at times while cruising around under light load.

Under light loads it dips just a bit, to around 56-58 but if I am cruising down a road at like 45 in third gear and punch it, the drop is like to the very low 50's and if on the highway at 65 in 6th gear when punched it drops, again, very little...but if I downshift to 4th it will drop into the low 50's again. Even at highway ramp speeds in 1st of 2nd, if I punch it the pressure goes down pretty far. I do not think I have seen 48, and it does not seem to have a pattern that I can peg down??