Engine/Transmission (1998.5 - 2002) Key on Lift Pump PSI

[pcarlson]

I was getting 7 psi when the key went to the on position now it reads 1-3 psi. Idle warm is 13-14, cruising is 12-13 psi. These numbers have dropped 1-2 psi from initial readings.



Is this initial key on psi a signal of things to come? From what I've read the ECM is supposed to cycle this on key on to 7 psi for priming.



Any insight?

 

[Whitmore]

If you simply turn the key on but dont crank the starter you get half power to the L/P and it lasts for a few seconds, then if you crank the starter but dont start the motor you get full voltage for like 27 seconds if I remember right, your numbers still sound good to me and I wouldnt worry about it but keep a good eye on that fuel pressure gauge!



cheers, Kevin

 

[CFAR]

Lift Pump Pigtail

Does anyone know what the pigtail that comes with a cummins lift pump is for?



My stock harness fits the plug on the cummins pump.

 

[klaybus]

LP Pigtail

On my 99 the electrical plug was permanently attached to the LP so when I had the LP replaced under warranty the pigtail was needed to attach the LP to the wiring harness... .



Clay



14-15 PSI Idle

13 PSI Cruising

10-11 WOT

 

[CFAR]

Yeah I thought it might be for the earlier versions.



Old LP

10-11psi-idle

5-7psi-65mph cruise

0psi-wot (never done)





New LP

14-15psi-idle

12-13psi-65 mph cruise

With the III's its hard to go wot, I did get it down to around 8psi.

 

[cmckinney]

You are supposed to get a measurement when you just turn the key to the accessory on mode?



I only get a pressure reading when my engine is running.



14 PSI Idle

12-13 60 MPH Flat land

7 PSI WOT



-CM

 

[Bigsaint]

I wouldn't sweat your key on, wait to start FP numbers. Mine varies day to day as well. Pump is running for a second or so.



CM... you will not get a FP reading when you switch to acc. mode, doesn't activate the pump.



Scott W.

 

[Chipstien]

Originally posted by pcarlson

I was getting 7 psi when the key went to the on position now it reads 1-3 psi. Idle warm is 13-14, cruising is 12-13 psi. These numbers have dropped 1-2 psi from initial readings.



Is this initial key on psi a signal of things to come? From what I've read the ECM is supposed to cycle this on key on to 7 psi for priming.



Any insight?

Your lift pump is bad if if your WOT pressure is under 10psi. Untill then don't worry.

 

[cmckinney]

Couldn't believe my eyes.



Was going down the interstate and glanced over at my FP guage. Read 1psi at 65mph.



Drove home shut down the engine and started it back up. Read 14 psi. Thought it was weird



Was driving to work this morning saw 14 psi at start up stayed at 12 while driving. No problem right? Wrong dropped to 1 psi again.



Truck is now at the dealer.



Do you guys know of any LP issues where you get good PSI then drops low likes this?



-CM

 

[duaneparks]

CM,



Seems like I've read in the past that this is a classic "failing lift pump" scenario.



Fluctuating pressures have preceeded many many lift pump total failures. Hope this helps.



Duane

 

[mpjmpj]

Scaring Me!

You guys are scaring me!!!!!!!!!



My Ram just turned 100k TODAY and I have never had a LP failure (but probably will now that I mentioned it).



Although, when WOT accelerating it starts to quit as if it is starving for fuel. I don't have a gauge for the FP and should probably get one.



Does adding a pusher pump help the LP or take it's place? Will this prevent future LP failures??



Where does one get a LP and a pusher pump at a reasonable price?



Thanks!



Mike

 

[rkressg]

old liftpump 0 psi any time

new liftpump 12 @ idle

9 psi driving

5 WOT



Isspro manual fuel gauge

 

[CFAR]

mpjmpj,

If I were you I would get a fp gauge, even it its only a temporary one. If you continue to drive with a bad or failing lift pump you could damage your vp44 =$900-1500. cheap insurance, especially since you are out of waranty.



Hopefully someone more informed than myself can help you with your pusher pump questions.



I didn't go wot because i knew it was pulling my fuel pressure down too low, I would suggest you keep as light a foot as possible until you get the fp checked.



lol

 

[mbrolin]

My first LP was erratic when it went out. One day it would it would be fine then drop pressure. After a few miles it would come back to normal read good for 2-3 days then act up again. The 2nd LP was good for about a mile then drop to 0. First LP went out in 11k and the second LP only lasted 7k.

 

[cmckinney]

Returned from the dealer with new LP.



Idle 14 PSI

60 MPH flat land 11 PSI

WOT ?? Haven't done that yet.



-CM

 

[jbone]

pcarlson, I would get my spare right now--don't know what part of alaska you live in, but heard it is big state!!!



mpjmpj, Man you need to get that gauge and change that pump right now--what others guys said that MP-44 is expensive!!!!



I want to be politically correct here also, but do the work yourself! Don't let the *tealer get there hands on it!!!

 

[mpjmpj]

Price and place?

Where is a reasonbly priced supplier of these lift pumps? Do I need to go to Cummins to get one or will NAPA have it ya think?



Sounds like I should get 2 since these things are mostly unreliable!



JUST ordered my PE Comp today and got a great deal on it too! $550 bucks delivered!!

 

[shaft]

Re: Scaring Me!

The symptoms you are describing are -exactly- what I experienced when my VP44 went south, my lift pump had been dead for sometime (month or so) when the VP44 started acting up... ...



With my PM3 on and at a high setting the truck would sputter at WOT... ... once that started it quickly progressed to the point that it would do it with the PM3 turned totally off (within about 50 to 60 miles of playing with it)... ... Then the VP44 totally died. I replaced the fuel lines and LP with the PE4200 kit from ADT and installed a newly rebuilt VP44 and all is well again... ...

Originally posted by mpjmpj

You guys are scaring me!!!!!!!!!



My Ram just turned 100k TODAY and I have never had a LP failure (but probably will now that I mentioned it).



Although, when WOT accelerating it starts to quit as if it is starving for fuel. I don't have a gauge for the FP and should probably get one.



Does adding a pusher pump help the LP or take it's place? Will this prevent future LP failures??



Where does one get a LP and a pusher pump at a reasonable price?



Thanks!



Mike

 

[ehenry]

Saved Injection Pump

Thanks to you guys and TDR, my injection pump is saved ---



just bought new lift pump due to installation of fuel pressure gauge which was inspired by you and warmer weather here in the east





Saw that the fuel pressure at idle was 9 psi wide open was towards 0



With new pump it is 14 psi at idle and just above 10 at wide open throttle



ps what is the pigtail for?





thank you

 

[mpjmpj]

Just so happens that I did the LP lastnight in the dark driveway. Lost one of the Cummins washers (but no leaks thank GOD). Don't have a pressure gauge yet but figured it was time to change the pump at 100k.



The truck runs better. Still haven't REALLY tested it though.



I have no idea what the pigtail was for. I put it on anyway, what the hell.