Yet another lift pump ? ('04 HO)

[NNethers]

Ok, I need some lift pump pressure advice for my ’04 HO. Before anyone says anything…yes, I did use the “search” function before I posted up this question.



I used a test gauge from GDP and used the test port on the billet fuel filter cap from Geno’s to get my readings. As you can see in my sig I’ve got a TST, 2 micron filter and big line kit from GDP and that’s about it for mods that would have any effect on the fuel pressure. The truck has 84K miles on it, I’ve owned it for about 10K of that and the TST has only been on there for about 3-5K miles.



I ran the following pressures (with TST on 4/4):



*at idle: 6-7psi

*Cruising: 5. 5psi

*WOT: 4-5psi



Are these acceptable? From what I’ve been able to find online here I guess the port on the Geno’s cap is PRE fuel filter(s) so I guess conceivably the pressure at the CP3 inlet would be less than what it’s reading at the fuel filter cap…. does that sound right?



I use the truck as a DD and tow 6-12 times a year a load of about 10-12K pounds and my overall goal with this rig is to get to about 500hp/800tq. I know that eventually I’ll have to get a lift pump to get to those goals but I want to know if I need one sooner than originally planned.



Thanks in advance for your help!!!

 

[steved]

Do you have the fuel bowl-mounted lift pump, or the intank... both found there way into the 04/04. 5 trucks...



If it is a fuel bowl-mounted LP, then the numbers sound low... they should be similar to the VP-44 trucks. You numbers sound like those of the in-tank LP.



Are you taking your reading before or after the 2-micron filter (are you getting the actually psi seen at the CP3)??



steved

 

[NNethers]

Do you have the fuel bowl-mounted lift pump, or the intank... both found there way into the 04/04. 5 trucks...



If it is a fuel bowl-mounted LP, then the numbers sound low... they should be similar to the VP-44 trucks. You numbers sound like those of the in-tank LP.



Are you taking your reading before or after the 2-micron filter (are you getting the actually psi seen at the CP3)??



steved

I’m not sure what I have in regards to which lift pump I’m running. I know the stock LP on these trucks were fuel filter mounted and the retrofit was in tank. Since I’ve owned the truck (about 6 months now) I haven’t replaced it. What’s the best way find out which pump I’m running?



The reading I’m getting is pre CP3, pre 2 micron GDP filter and I believe it’s even pre stock filter. I’m taking the reading from the port on the top of the Geno’s garage billet fuel filter cap.

 

[steved]

You should be able to hear the LP under the hood buzz when you turn the key to "on". IIRC, I believe guys do say the in-tank pump will also whine when the key is turned "on", but obviously from the tank.

If those numbers are from a fuel bowl-mounted pump, they are low if memory serves me correctly. Idle should be around 10psi with the bowl-mounted pump...

I would be curious to see what your getting at the CP3... as long as you are above 0psi@WOT at the CP3, the CP3 should be happy. But I know they run better with pressures pushing 20psi at the CP3.

steved

 

[NNethers]

I definitely hear the buzz from the LP, pretty sure it's coming from under the hood. I'll have to have the wife operate the ignition while I listen for it under the hood.



Assuming it's coming from under the hood it appears as though my LP might be a little on the weak side. If that's the case…I guess I'll be calling GDP here pretty quickly. Time for a walbro and some LP and IP fuel pressure gauges as well.

 

[RMalone]

The filter canister mounted pump is on the back side of the canister, it is cylindrical and plastic. I think your numbers are about right for a canister mounted pump, except I would expect you to hit 0psi on wot. If any stock pump is giving those #'s through a 2-mic filter I would say it is working fine. My stock pump ran 8psi at idle, about 5psi at cruise and zero at wot, stock filtration.

 

[JBallou]

I am in agreement with RMalone. sounds OK to me if no drivablity problems.