I finally changed the LP on my 02 2500 4x4 auto. Was reading about 10-11 idle and down to 3 WOT The install was easy enough everything is tight with no leaks new fuel filter as well old filter had only 7000 miles and was clean.

Question is I'm now getting 16psi idle , 12-13 cruising but down to 8 at WOT. Is this pump good or is it bad. Anyway you look at it it's still better than it was and better then the new in-tank pump but I was surprised at the 8-9psi at WOT with no mods, It was a Carter replacement bought at Pep Boys for $175. Is this normal? I keep reading but most can't drag the WOT below 10 with bombs.

Thanks
Bill.

 

Have you replaced the banjo bolts and put in larger lines? This could make a difference.

 

That does sound a touch low.

I have a Carter pump with the Vulcan Relocation and Big Line kit. I never had a baseline for my f/p, cause I installed the Vulcan kit the same day I put the gauges in.

My #'s are

15-15.5 Idle
13.5-14 Cruise
12-13 WOT

STOCK truck, with only exhaust and BHAF.

As I said, I can't tell you what my #'s were so I'm not much help.

I can tell you now that I have what I have, 8 psi would kinda bother me. I would suspect that 8 would/could become 6 or 7 with some fueling mods.

 

Ya know, I just talked to a Cummins tech that says we are all wet about fuel pressure PSI. It's volume of fuel over PSI. He told me as long as I'm getting 50 oz's per 25 seconds I'm good to go. But I'm replacing it with a FASS II anyway. I just don't like the idea of pulling it down past 5 PSI WOT.

 

I would buy into that (the volume v.s pressure thing)
Smallest orfice on my system is about 3/8" at the input side of the lift pump.

I think at the very minimun people with increased fuel line diameter see less of a difference in psi between idle and go time. Just measuring the amount of fuel in the lines v.s a stock set up, there is probably about double the volume.
I'm not a scientist or diesel tech, just thinking out loud.

 

So the Vulcan kit sounds good but do I need it with the numbers listed, somehow I killed the money tree in the back yard . I use the truck as a DD and to haul our 7k camper.

 

FP sounds about right. I am running the Bully Dog fuel management system and i am at 22psi idle and 15 wot when running 5x5 on my comp.

 

Need?, no.

 

Your right on the mark with me...

Starter Bump 15.5 - 16.0 PSI
Idle............. 14.0 - 14.5 PSI
Cruise 65 MPH 11.0 - 12.5 PSI
WOT............ 7.5 - 8.0 PSI

This is a stock pump. NOT a intank either...

 

I've had it with the stock setup and waiting for the Walbro threads to make sence.

 

Yes, that is correct, but since pressure is just the measured resistance to flow, higher pressure = higher flow. It is return flow under pressure that keeps the VP44 cooled and lubricated......if you flow more fuel through it, the pressure will be higher. The Cummins flow test is a VERY poor way to measure LP performance since all they attempt to test is free-flow fuel volume. This test completely disregards the fact that when put under pressure, like when the LP is operating in the fuel system, flow will be reduced drastically - especially on a marginal pump that might be in question. It is perfectly possible for a half baked LP to easily pass the free-flow test and perform unsatisfactorally when under pressure. Monitoring LP pressure is still an adequate way to rate LP performance.

 

OK, it's getting worse. After less than 75 miles I can drag the WOT down to 6psi. This pump is only 4 days old and driven 2 days. Should I take it back? Pressure at idle and cruse are unchanged 16 idle and 12-14 cruse.

Bill.

 

6 psi is getting close to your limit on the low side. The stock banjo's are the most restrictive part in my opinion.

 

I would, my new LP won't drop below 11-12 WOT.

 

Exactly! Upgrade your fuel lines and you'll have all the pressure you want. With my bombs I can't pull below 10psi a WOT. DON'T go with the over sized banjo bolts. For me it was a waste of $$ (no improvment at all). Spend a little more and change the fuel lines. My brother is running the Vulcan kit and I'm running whats in my sig and they both work well. There are other kits available (Scotty's) just do a search. BTW my lift pump is still in the stock location as well. Good luck, Phil