Another Lift Pump ???

[Archive]

I know this topic has been beaten to death, but still have questions...

I finally got my FP gauge hooked up. (Its been in the pillar for 10 months. ) My pressure is a little low; 11-12 at idle, 8-9 cruising, 3. 5-4. 5 at WOT. . (3000rpms in 3rd and 4th gears)(I'll try a new filter tomorrow. ) The guage is hooked to the test port at the VP44. (On a stock truck. )

My question is, what normally goes out on the Liftpumps?? At idle sometimes it is 12, you give it throatal, the psi drops, but only returns to 11, sometimes 11. 5 others 12. . kind of like the bypass or regulator is sticking. . Is this what goes out??

#2 question... How long after you turn the key off, should the psi remain in the system. . (It seems I have seen other members trucks sitting off with fuel pressure. ) My FP will hit 0 before then engine stops turning. . how normal is this. .

Thanks for the help. .

Bryan



(JDGnutt@aol.com)

 

[Bigsaint]

Bryan, from what I've seen with dying lift pumps, here's what you will see...



FP will be lower than what you typically see, whether at idle or at WOT. I wouldn't be too concerned right now if it sometimes rebounds to 12 psi's at idle and sometimes rebounds less, by about 1 psi. Even with the new aftermarket pump I'm running now, I see anywhere from 15-16 psi's at idle. How long the truck has been running, fuel temp. , grid heaters cycling, etc. , all can effect the FP to a certain extend. Right now, being that you just installed the gauge, get a baseline and then watch for the FP to be consistantly lower, that will be your first indication of a dying pump.



When the pump is close to death, I normally see very erratic psi's under throttle. The gauge needle will actually jump around from a 5 psi ( more or less) reading, i. e. , you will see 10 psi's then it will drop right to 5 psi's then back to 10 psi's, under the same amount of throttle, rather than transition smoothly downward under hard throttle.



As to your other question, I have two FP gauges. One is with the electric sender and the other is a mechanical FP gauge. Both drop right to 0 psi's when I turn the truck off. Needless to say the electric gauge will not read without power, but if I shut down but leave the ign. keyed on, it still drops right to 0 psi's. When you key on ( wait to start) you should see the mechanical gauge jump right to your typical FP reading at idle and then drop slowly back to 0 psi's. My electric gauge seldom reads anything above 3 psi's at the initial key on ( wait to start) setting.



Hope this helps !!!



Scott W.

 

[Chipstien]

When you end up needing a new pump, move it to the back by the tank.

 

[TowPro]

ON both factory pumps I had die, both had the pressure valve go bad. I don't see how moving the location of the pump will help that problem. Also looking at the thread about "revisions of lift pump" all the changes affect this pressure valve.



But I am installing a new pump back by the tank, only not the stock stuff.

Originally posted by Chipstien

When you end up needing a new pump, move it to the back by the tank.

 

[CoastyAV8R]

I think your lift pump pressures are at a level where, according to the manual, you should replace it. Also in the latest TDR mag, they said that pressures that low under WOT conditions are out of specs and should be warrantied. I'm sorry I don't have the mag or my shop manual here in front of me, so I can't quote you exact numbers. If you have the shop manual, look at it for the lift pump pressure numbers. Also look in the latest TDR mag as they have pressure limits in there also. I think they said the injection pump needs 7 psi for proper cooling.

When my lift pump died, it just started going to 3 psi one day. It only did it sporadically, sometimes it would come back to around 12 psi and sometimes it would just stay at 3 psi. I thought my gauge was shorting out or had air in the lines. After messing with the gauge for a week and finding nothing wrong I put in a new lift pump and the pressure was 15 psi.



Pat

2001 ETH QC 4x4

 

[Ross]

4th lift pump going in!

Well, at 108K, my 3rd pump took a crap on me today. It went in almost exactly a year ago, at 88K. I had a prior replacement go out at 43K. Both pumps were replaced under warrantee. The dealer let me install them because my rig was a long way from town... . At any rate, they are not warrantee-ing this last one because now the truck has over 100K on it, never mind the fact that the pump hardly has 1-year and 20K miles on it. At a couple hundred dollars a pop, I can't get excited about replacing this one with another cheap P. O. S. pump that may or may not make it a year... ... .



I have seen here on the TDR that to date, there's no real long-term solution yet.



Any suggestions?



I need to get the truck back on the road immediately. .

 

[JR2]

Here is what I would do... go to your local cummins shop an buy the pump for $140 and install it in the stock location, while you are there buy two and carry one with you. Later when you have time, install the pump back by the tank. Its easier to replace and easier on the pump.

 

[1tuffram]

How to test WOT pressures??

I got my gauges from Brair Hopper (add me to the growing list of two big thumbs-ups for the quality of his stuff. I'm impressed with the quality and trust me I'm VERY nit-picky and hard to impress). My question is how do I PROPERLY test fuel pressures at WOT?? Do I stomp on the go pedal while parked, take her out on the highway and floor it, or find a big ol'hill and load the engine up as much as possible with the pedal to the metal??



How does the stealer test WOT pressures, thought I heard they just stomp on the go pedal in the service bay and call it good. Doesn't seem like a none loaded WOT run would be a good representation of real world fuel pressures.

 

[Joe Mc]

Under 10# @ any condition merits replacement

Bryan,



If my memory serves me the service manual states (WTE) any pressure 10 or less, regardless of throttle position, merits replacement. I told my dealer that I checked the pressure pre and post filter (. 5 differential new filter), gave him the readings and told him the truck was performing poorly. New lift pump installed. Pressures before (utilizing Briars FP 'test' gauge @ post filter port) 6# idle, 3-5 moderate cruise, 1-2 mild acceleration and the big "0" @ WOT. After new pump 15 - 16 ilde, 13 - 14 moderate cruise, very little change under moderate acceleration and never less than 11 @ WOT. I'm stone stock BTW. Hope this helps. If you are out of warranty take $168. 00 + tax when you go to Cummins, otherwise be prepared to fork out about $330. 00 to the stealer.



Joe Mc

 

[Bigsaint]

1tuffram, you have to do the WOT test while driving for a true reading, running the RPM's up while standing still will not challenge the pump. Do as you said in your post, find a long hill and push it hard. If you have a adjustable fueling box, set it on kill and watch your egt's while you watch your FP. This will tell you what psi's you have at WOT.



Scott W.

 

[Archive]

Thanks for the info guys... Everyone seems to be telling me what I didn't what to hear. . (I knew when I put the guage on. . but still didn't want to believe it. ) I didn't get the new filter in, but I did haul a load. . I did see 3psi a few times at high rpm's. I guess the reason I am worried about it is I will be adding a major fueling box in the very near future. . and 3psi stock, will probably be a -0 with the box.

I only have about 38,000 on the truck, so the pump should be covered. . I just get way uncool when I even have to think about someone else touching my truck. . especially a stealer... (it has nuthing to do with the fact that I was asked to leave the service department, last time my truck was there. . (I'm not sure if it was me telling the guy how to fix my truck. . :-{} or when I tried to show him... )



On mine. . just stilling still you can give it some pedal and watch the psi drop. . about to 7-8... (sitting still)



I'll put a new filter in the first of next week, to confirm my dying pump...

Thanks guys. .

Bryan



(JDGnutt@aol.com)