Hey folks..i was wondering if any knows what the fuel pressure should be on a 04 Lightning. If anyone knows where it should be at say idle and WOT that would be great....we have a truck that is kinda nosing over at 3400rpm at WOT and think it may be the pressure regulator or maybe something else...but i think this is a good place to start. If anyone knows that would be great...thanks.
Vince

 

32 idle 52 WOT

 

20lbs spike from 8lbs boost?

 

Yup

 

The Lightning uses a stepped voltage fuel system. When not at WOT (2.93 volts TP and lower), the ground side of the fuel pumps go through a dropping resistor cutting the voltage down to aboout 7 volts. When you go WOT (over 2.93 volts TP), a relay switches the pumps over to full ground, hence the huge raise in fuel pressure. If you have a fuel pressure gauge on the truck, you can actually watch the fuel pressure switch on and off when you tip in and out of the throttle moderately.

 

my autometer electronic guage reads about 33lbs at idle to about 53lbs at wot. If i rev the engine, the guage almost goes with the tach. There is a slight delay but it's kinda in synch.

 

Jeez, is my feul pressure low?

At idle, mine sits at about 30lbs. WOT, I would guess its around 48 - 50.

 

Wow thanks guys..escpecially you Sal.....kicking myself for not visiting the boards here as much as i used to. Now i remeber why i first came here. Sal this truck is kinda odd....it ran 13.1@106mph..makes 418/520 at the wheels while nosing over at about 70mph then picking back up. He kicke don his power cooler and it slowed to a 13.6 then 13.8 on the next runs which were NOT back to back it say for a bit although it was warm and humid out.....we are going to get a guage on it to see if it is the fuel pressure regulator....i have heard of a few going bad..namely MM&FF's project truck. Thanks again...Sal next time i see you at the track i will say hi this time....lol..
I will let you know what comes of the guage testing.

 

How much fuel did you have in the tank/my truck was doing the same as yours,If i keep around a 1/4 tank no problem

 

It wasnt low on fuel cause he drove it back home and around for like 2 days..and it still has fuel in it now.

 

Ditto...

 

did you guys install aftermarket throttle bodies??? If so, do the voltage check to make sure it is adjusted correctly!!

 

Also you are not getting a 20 lb increase in fuel pressure just from the 8 lbs boost.
When you crack the throttle the engine goes from 20" of vaccum to 8 lbs boost. If you were to pull the vaccum boost line off the fuel pressure regulator it would pick up some 10lbs of fuel pressure just from the vaccum loss.