Engine/Transmission (1998.5 - 2002) Lift Pump fine until...

[CORed]

Hey all...



I have read tons of lift-pump threads and related info, so I am a bit surprised and worried when I see my lift pump act as follows.



First off, normal for me was 13 idle, 10-11 driving and 7-9 WOT.



Just two days ago, I'm driving around and notice my pressure around 3-4. I think, crap, lift-pump finally going out at 41,500 miles. I have no mods BTW.



Well, then, the next morning, I disconnect, clean, and reconnect all connections to on my Westach sender under the hood. Start the truck up and I'm at about 13 lbs. I think, cool, just a bad connection. Well, here is where it gets weird.



I give it gas to drive away, and the pressure drops to 0-1 driving and 3. 5 at idle. I drive to work, order a liftpump from Cummins Rocky Mountain, and after work, go out to the truck and start it... again, almost 13 lbs at idle. As soon as I use the throttle to pull away from the parking spot, it all drops to 0-1 driving and 3. 5 idle again. It stays this way all the way home.



Any ideas? I have a lift-pump coming on Monday, but I'm wondering if it is something more major like a control board or something since it shows 13 until I use the throttle.



I'd take it to the dealer, but I wonder if it would "pass their test" and fail it. :-{}



Steve



p. s. I'm not driving the truck.

 

[John - K5AWO]

I don't think your lift pump can supply the volume need to fuel the engine when you load it.



Don't be pushing it very hard until you get it replaced. The VP44 wants 8 psi to be happy (or at least that is what Dodge wants).



I read somewhere that the VP44 can run with a 2" vacuum and be quite happy. Not for me though, I am not that brave with my purse strings.

 

[Gary - K7GLD]

Seems to be a pretty typical scenario when they fail - but you probably already knew that from past threads. Sure would be interesting to carefully disassemble the pump part for an autopsy...

 

[Joe Mc]

CORed - sounds real familiar. Especially the part about the Westach fuel gage. Mine did the same thing and I replaced the lift pump. # 2 after 100 k warranty, # ???? within warranty. Anyway, with this being pump #2 after warranty (on my dime) I decided to relocate the pump & stock fuel filter closer to the tank. Not a bad project. Took some angle w/holes and fab'ed up some hanger brackets and all went fairly well.



Back to the Westach part of this . . . Shortly after the new pump & relocate I noticed a bit of fluctuation, then it would drop to 10, 5, & 0!!! #%&*+! I thought another bad pump from Cummins. I had fought & won with Cummins last time I purchased a pump it didn't make 10 PSI - they cut me a check and didn't want the pump back.



Here's the deal - when the pressure drops from the normal - I tap on the (A-Pillar mounted) gage and it pops back to normal. Hum, so I'm glad I kept the pump - at least I have a spare.



Some day soon I'll remove the tri A pillar gage assy and check the gage for loose connections, as that's what seems to be the problem.



Sorry for the long reply.

 

[Gary - K7GLD]

It'a always a good idea to verify PSI with a second guage - preferably a mechanical one if possible... A simple mechanical guage as used in domestic water systems, and available at hardware stores will do the job, and only run about $15 - I have one for that purpose, and to take to Dodge group meets - you'd be surprised at the percentage of weak/failed pumps we have discovered...

 

[GIT-R-DONE]

Although it does sound kinda weird, this could be a few things here. Could be the pump on its way out,and could be the gauge. If there is a way to check the pressure with a different gauge, preferably a manual gauge, I would do that first.



As far as the dealer is concerned,"passing the test", when I went through my first and only lift pump, the Service manager said there was no longer a requirement of passing the test, they just were going to replace it. If the truck is still under the warranty, have the dealer replace it.



I instead went with the FASS system as I figured I wasn't going to keep chasing the lift pump problem, so I did away with it all together.

 

[CORed]

Whewwww!



You guys have made me feel better and much less worried. Thanks for all your replies!!



I am considering taking it to the dealer and just keeping the pump I ordered for myself. The reason I hesitated going to the dealer is I just installed the larger banjo bolts and they will obviously notice them. But since it would probably only take 20 minutes to change them back out (and a little fuel on the garage floor), I may just change them back and take it in. Hopefully the pump will be able to refill the filter housing and get me to the dealer.



Either way, I'll post back with results just to end this thread with a resolution (hopefully).



Steve

 

[Sticks]

I am kind of going through the same thing. My pressure is normally 15 at idle, and lately it will drop to 7. 5 (issopro mechanical gauge). I can get out and disconnect and reconnect the LP wires and the pressure will jump back to 15 for a while but eventually drops back to 7. 5. I have a couple of old LP's that I have acquired so I may change them out. I moved my LP to the frame, so bye bye warranty.



I remember reading somewhere that there is a circuit that drops the voltage to the LP (I think) under certain conditions. Could this be a circuit or relay problem?

 

[dresslered]

If you're reading good pressures at idle and low pressures under load, it is very unlikely that it is the gauge. With 41,500 miles on the orginal lift pump, my money would be on this being the culprit. You are very wise for not driving the truck until you get your new one. You might save $150 going to the dealer for warantee, but you'll do unknown damage to the VP44. Send Daimler-Chrysler the bill for the replacement pump stating that you couldn't make it to the dealer. They have reibursed me twice for lift pumps that I have replaced.



On the long shot that it isn't the lift pump, it is always a good idea to keep a spare under the rear seat. I've had one go out sloooowly over 10,000-miles and then I had another one that would just instantly stick in a low-pressure state.

 

[kscheffler]

Vent Air Out of Sender Line

I have similar problems with my SPA guage. I have since installed a vent valve before the sendor connection. Seem like every three months air builds up in the line. Once I vent the line the problem goes away. I think what is happening is that the fuel does have entrained air and it travels to the high spot in the line over time. Hence the reason to install a FASS air seperator. Oh yea you should only vent when the truck is NOT running. Seems strange but it works better to vent when the engine is off.

 

[rblomquist]

Originally posted by Gary - KJ6Q

It'a always a good idea to verify PSI with a second guage - preferably a mechanical one if possible... A simple mechanical guage as used in domestic water systems, and available at hardware stores will do the job, and only run about $15 -

Totally agree about having a back up mechanical "test" gauge. I've had a couple of worries and turned out to be loose ground on the sending unit not the LP. I bought a briar hopper one which was nice because I didn't have to mess around with putting one together (although it's not that hard).

 

[CORed]

Just finished installing the new lift pump from Cummins RM. Took about 45 minutes and I took my time.



The liftpump was the culprit. After bumping the starter twice, the truck started just fine and idle pressures are over 15lbs. I'm totally psyched!!! I took it for a drive around the block and it ran flawlessly... not even any hiccups. Seemed normal driving pressures were around 13. It's never been that high since I bought the truck used at 23,500 miles.



Anyone want to diagnose the old liftpump is welcome to it for the cost of shipping.



Unless anything weird happens with this pump, this should be the end of story. Thanks for all the suggestions, including the air in the lines suggestion. But with the new liftpump, I couldn't be happier.



Can't wait to see what WOT shows as I reserved myself tonight and didn't want to tick off the neighbors.



dresslered... please send me more info on where you specifically sent the "bill" to Daimler-Chrysler. I'd like to do the same thing since I know it is a warranty part.



Thanks to the TDR!!!

Steve

 

[Hohn]

I wish I knew why a LP would allow pressure to vary SO MUCH from idle to any kind of pedal application. Maybe it just shows how little fuel is actually being used when idling?



justin

 

[GIT-R-DONE]

Now, go buy another one to stick behind the seat, as you dont know when this one is going to stop working either.

 

[dresslered]

This is where I sent my lift pump bills for total reimbursement (include VIN and mileage). Include a well-written letter and offer them the old pump. In my case, I have an incompetent dealer who didn't even know what a lift pump was.





Daimler-Chrysler Customer Center

P. O. Box 21-8004

Auburn Hills, MI 48321-8004





In both cases, the check arrived after about 4-weeks. They included the cost for the pump, overnight shipping, and in one case, even my Power Booster's membership fee (gets discount pricing).

 

[plongson]

What is the latest and greatest Cummins part number for a LP for a 99'? I am heading out on a road trip to central Nevada in a couple of weeks and would feel beter if I had a spare under the seat.



ALSO... .



Are you guys changing the LP from on top or from under?? It looks challanging from the top... I have big hands



Paul. .

 

[AKAMAC]

3990105

plongson,



I just got mine from a TDR member. The price was 126. 95 to my door. His shop # is 812-473-5604. Not bad for a new LP. Mike

 

[Gary - K7GLD]

I swapped out my LP when I thought it had a problem - it didn't - and I did it from the topside - the mounting bolts are on top. and don't see how it COULD be done from below...

 

[CORed]

The latest part # I just purchased from Cummins Rocky Mountain was 3990082. This is the pump and the new harness. Not sure what the new harness is suppose to improve, but it was cheaper WITH the harness than without by about $1. I believe the part # for just the pump alone was 39900108 or close. The new harness was just a 10-inch wire with connectors on both ends. I added it to the existing connector and plugged the other end into the pump.



I installed it from the top. Didn't have to disconnect anything to do it. But normally only one hand could fit down in there at a time.



I see 15 at idle and 12-13 normal driving. I have 4 of the 5 larger banjos installed. I haven't installed the one going into the VP44 as I have my fuel pressure gauge there and don't have the Schrader valve insert for the new bolt. Trying to figure out where to source one of those but that's another story.



Steve

 

[Diesel Gunner]

48K and I am on my third LP. First one died a slow death. Second one leaked like a sieve. My third one is dieing the slow death.



DC is going to pay for as long as I can shove them down their throat.



I have had one Westach sending unit fail so far. I now believe that I have a second one that has failed. I am monitoring pre and post filter. This second sender gives that same 13. 5psi reading no matter what. It is mounted pre filter. The other sender is post and gives what I consider to be accurate readings. It was just replaced a few months back.



When I am out of warranty for these junk modules I will buy the FASS. Why won't I do it now? Because DC needs to pay for as many of these as possible. The dealer that I use does not even question me when I bring the truck in. And, I don't wait until they drop to 5 or 6 psi. When they hit 10psi at idle the dealer sees my purdy face. They know what I want.