Engine/Transmission (1998.5 - 2002) Fuel Pressure Standards

[KOREDISH]

I know this isn't a new topic, but it seems everyone gets different pressure readings, which I find perplexing. I just checked mine and I get 12psi at idle, and at high idle little less. I can't check under load as of yet, but working on it. My truck doesn't cut out or anything, so wondering if this is low or within range? The service manual says anything over 10 psi is acceptable at idle. You would think there would be consistancy in a mechanical device.





Thanks

 

[Dkevdog]

I keep hearing 7psi- if you go below that, then that is when you have to start thinking about replacement. I think you're numbers are fine. I get about the same- 12-13 at idle, and about 10 running down the road at 70. If I hammer it, or am pulling a grade, I've seen it briefly swoop down to 5 or 6. Have a friend with the exact same truck and guage, he gets 14 at idle and 11-12 on the road. I have a newer pump than he does(replaced) but he has a stock truck. I'm sure the fueling boxes and larger injectors make a difference.



Kev

 

[KOREDISH]

Fuel System Enhancements

Originally posted by Dkevdog

I keep hearing 7psi- if you go below that, then that is when you have to start thinking about replacement. I think you're numbers are fine. I get about the same- 12-13 at idle, and about 10 running down the road at 70. If I hammer it, or am pulling a grade, I've seen it briefly swoop down to 5 or 6. Have a friend with the exact same truck and guage, he gets 14 at idle and 11-12 on the road. I have a newer pump than he does(replaced) but he has a stock truck. I'm sure the fueling boxes and larger injectors make a difference.



Kev

I think that if you go to a comp box and big injectors or even EZ and big injectors, I would enhance my fuel system with after market stuff.

 

[WadePatton]

Idle speed reading is pretty much useless. All it tells you is that the pump is running. The number that matters is the high RPM/high boost situation. Put your test unit on a long enough hose (like Briar Hopper's) to reach the windsheild, then tape it up there and go for a drive.



Stock fueling-shouldn't pull it below 6-8 psi. With the UFM on 5x5 it'll go down to 1. 5-2. Add big injectors and I can now get it down to zero on level 3.



My lift pump is working just like it did when I put it on 30k miles ago. I'm just sucking the fuel out faster than the lines will flow it.



Fuel upgrade kit is somewhere in the mail.

 

[Oil Burner]

i have found, thu 2 pumps, that with STOCK fueling, you can pull a pump down about 7 or 8 psi from idle pressure under WOT. that's just my experience, nothing scientific here. my old pump in the end idled at 8psi and went to about zero under WOT. new one is 14 or 15 at idle and 7. 5 or 8 at WOT.

just my . 02

~Jason

 

[IWeiny]

Chiming in with my experience.

I had a pump go bad way back around 40-50K miles. Don't remember the mileage. At the time I was not a TDR member. Now that I am I have put a FP guage on, 70K miles. I don't know if my pump is good or not.



I am seeing 9-10 at Idle and down to 5-6 at WOT. I have not however been fully loaded. Just WOT with the camper up a steep local grade to check the FP.



I am thinking the pump is good but the filter is dirty. Will be changing the filter soon.



Interestingly enough I was worried about putting an EZ box on with "low" FP but it seems the pressure is running higher with the EZ. Of course I really don't need WOT now with just the camper...



Also I found that running with a full tank increases the pressure. I heard that on this forum somewhere but I took note after getting the guage. So the extra head in the tank does help. Might be a good emergency tacktic if a pump goes bad in the field.



Ira

 

[RustyJC]

With truck as equipped below and towing our 13,500 lb 5ver:



Idle: 16+ pre-filter; 16+ post-filter

70 MPH cruise: 15 psi pre-filter; 14. 5 psi post-filter

WOT: 13-14 psi pre-filter; 12-13 psi post-filter



This is with original lift pump @ 15,000 miles. Fuel filter was changed around 12,000 miles.



Rusty

 

[Diesel Freak]

Running stock LP here... relocated aft of the Xfercase ,and all banjo fittings are in the trash.



Idle... just over 15 psi with new pump from Cummins



70 MPH~2000 RPM pressure drops to 13-13. 5 psi



WOT with box on, it drops to about 7 PSI (this is with 427 HP on tap, ie. DD3's , Edge EZ, and an old Blue Box with some FREAKY program that does not defuel till 3200 RPM)