Lift(Transfer) Pump Question

[Bill Stockard]

Has anyone tried the Cummins lift pump used in motorhome application--275 HP ISB? Cummins Part No. 3990105 which is supposedly speced to provide a higher GPH and a minimum of 14 PSI at WOT. It fits in place of the stock lift pump used in Dodge truck applications. The only thing that is different is the wiring harness connector.



I and some of my friends have already experienced low lift pump pressures/no lift pump pressure and lift pump replacement in our trucks with under 30,000 miles on them.



Just curious... .....



Bill

 

[**ICEMAN**]

thats the one i just requested to be installed at the dealer for the one that died(01. 5 bombed dyno results) dave d posted that you need the wiring harness for 98. 5-99 trucks($7). 00-01's hook right up.

 

[KatDiesel]

Originally posted by **ICEMAN**

thats the one i just requested to be installed at the dealer for the one that died(01. 5 bombed dyno results) dave d posted that you need the wiring harness for 98. 5-99 trucks($7). 00-01's hook right up.

So you took your truck in and they are replacing it? Just curious.

 

[24V-DSL]

that's the one....

I just bought one for a back-up when I need. This is the latest revision per mother Cummins. The 01 trucks don't need the harness.



I just got my fuel pressure gauge installed and my readings are 14psi at idle, 12psi at 60-65 mph. and 4-7 at WOT (the 4 only happened once, the rest have been ~6) This is the only reading I'm a little worried about, but so far I think my factory pump is working fine at 16K.

 

[hammersley]

Man you guys really have me screwed up with this lift pump. I've heard folks say they have to check the gauge to see if they have a problem. If you need to check a guage, and there is not a driveability problem(a Noticeable one) isn't this like rebuilding the motor at 10,000 miles?

Ok - where do you get a fuel pressure gauge, i. e. is it hooked up only for diagnosis or permanently on the A post etc. Exactly where do you hook it up and is it a hard job? Will the dealer check the pressure for you and let you know - I use Timberline in Portland.

 

[Chipstien]

I've heard folks say they have to check the gauge to see if they have a problem. If you need to check a guage, and there is not a driveability problem(a Noticeable one) isn't this like rebuilding the motor at 10,000 miles?

I second this motion! After reading the post about miles on your truck and problems that you have had, I am really worried about my pump. I don't notice any difference from the day I bought it and yet it still makes me wonder. What are symptoms of a bad lift pump. If it does have low pressure, what will happen. Does it cause other parts to fail, ie. injector pump, or is strictly performance losses. As it is, It seems to be something that is going to go out regardless, so why not change it before it does. What is everyone replacing them with, and what is the part #.

 

[DEZLPWR]

I too am confused about the lift pump problems. It sure seems to me like people are replacing them more because of the "bad" fuel pressure readings vs. noticible engine/drivability problems specifically caused by the bad lift pump. Is it possible for a truck to have a bad lift pump for 50,000 mi and not show any signs of it being bad? How do I get my lift pump replaced under warranty by the Dodge Dealer if it is bad, but it is not showing any signs of it being bad when driven? (besides the bad fuel pressure readings) Will a bad lift pump shorten the life of the injection pump?



Would some of the experts out there please enlighten us?



I can't figure out why this lift pump problem is so seldom discussed in TDR Magazine. As much as this issue is discussed on the forums, there should be a BIG write-up on it by someone @ TDR to help clear up the confusion.



Hint, hint... ... TDR Magazine people are you reading

this????



Steve

 

[**ICEMAN**]

kat,,yep,it's at the dealer. i talked to the diesel tech and he said he wasn't aware of the revised pump# but he will get the one i requested. ( we will see?) he also stated that most of the ones he replaces that have actually died while being drivin usally trash the vp44 also.



SCooke,,fuel is lubrication for the vp44. lack of fuel=lack of lubrication. so , yes, a bad lift pump will harm the pump

 

[Bill Stockard]

Hey guys,



Here's the post where I thought I had a fuel filter problem, but it turned out to be the lift pump.



https://www.turbodieselregister.com/forums/showthread.php?s=&threadid=11626



I doubted it was a fuel filter probelm since the new filter had been on about 700 miles and the cartridge was very clean when I took it out.



After my dealer's service department checked the pressure, there was no doubt what to do. I haven't had any more problems(knock on wood)..... yet. We've hauled the Lance on 2 trips to Colorado, Wyoming, and New Mexico and climbed lots of steep grades(high revs & heavy throttle) with no problems.



Bill

 

[Briar Hopper]

Like Iceman says, fuel is lubrication/cooling for the VP44 injection pump, so yes, a bad lift pump CAN harm the injection pump. The symptoms of failure are so slight as to be almost unnoticeable. A small loss in performance, engine running a little rougher than normal. Get gauges. The only other option is to have $$$ set aside for replacing your injection pump when it fails, and it might fail past the date your 100,000 mile Cummins warranty expires...

In 58,000 miles on my '01, I've had 3 fail. The first one was already dead by the time I got my fuel pressure gauge installed.

 

[Steve St.Laurent]

SCooke - I will have an article in the next magazine regarding the lift pump issues. There has been stuff in the magazine before, but there hasn't been a lot of research going into alternatives (there has been some) until a few months ago, the deadline for getting stuff into the last issue was way back in June. There is a HUGE lead time to get the magazine out.



The problem with waiting until there's a driveability problem is that by that time it's WAY too late. A MINIMUM of 70% of the fuel that is delivered to the VP44 is supposed to be returned to the tank for cooling and lubrication. Let's say your lift pump is only producing 50% of what it should - that 50% will ALL come out of the 70% that should be returned to your tank. So now you only have 20% going back to the tank - there is a performance different, it's just that you won't notice it until it's too late. Now you are looking at an injection pump replacement in addition to the lift pump!



Hammersly - check out the link in my signature "SW fuel pressure gauge" for installation instructions on putting a fuel pressure gauge in the cab.

 

[D6Diesel]

As a newby it's been an interesting read. My truck is stock with no extra gauges. I thinking of installing the upgrade lift pump when I install Ray's banjo bolts along with pre and post filter pressure gauges (along with fuel filter change). If I have to depressurize the fuel system and work on fittings and gauges, why not upgrade the lift pump while I there?

 

[JTBMC]

5 pounds of preasure is all you need

I got the # 3990105 from Cummins on the 5th of July installed the 1st one and walla no fuel preasure at idle. Returned pump to Cummins Mid South in New Orleans and was told I had to purchase another pump 140 Bucks and they ( Cummins ) would send 1st pump in for warrenty replacement. Also told by Shop Formen that 5 pounds at idle on the inlet side of the filter is all the VP-44 needs for cooling or fueling, and it was common to see 0 preasure to 2 # at WOT. Also you Dodge Guys should go to Dodge for parts and repair. I said, Sir I repair my own equipment not you or Dodge and left in a hurry rather than telling him he was an IDIOT. I really felt slapping his ears off would do us both some good. Well no refund and I'm still waiting for my now spare pump to be returned .

Tom

 

[csutton7]

You can either mount a permanent guage on the A-pillar or a pod or whereever--this will give you instantaneous readings ---or you can set yourself up a guage to keep in the toolbox, garage or... . to take periodical readings---most of us prefer the permanent mounted guage as these lift pumps can and will go out at anytime---sometimes you won't notice any performance changes and sometimes you will--it's really kind of weird--you're taking chances without the guage, but hey what are warranties for--it's just that it may go out when you don't want it too---you could do a search and read for a year on what's been done, what people think and what's the next move---there are varying opinions--the bottom line is we all want reliability in a pump--hope this helps---chris

 

[stephen bolger]

Help I have a 2000 ram. The fuel tranfer pump is dead . the dealer ship did the fuel pressure test 14psi @ idle 4 @wot no load on motor. what else could go wrong or should I have checked. the truck has 128000 km on it now.

 

[csutton7]

put a new lift/transfer pump on and see how it runs-most likely you're OK, but you never know untli you put on a new pump and test it--if you do a search you'll find that some guys are using dealer replacement pumps in the stock location, others are relocating the pump back by the tank, others using aftermarket pumps and still others are using a 2 pump set up---you need to decide what you think is best and go from there--good luck.....

 

[redneckdr]

lift pump

yesterday's BOMBing was to add a pusher pump, back by the tank. i elected to try an aftermarket universal pump. $40+ at the local parts store, 3/8" i/o. hooked it thru a second switch to switched 12v, and a relay. i used a pump with about 70gph capacity and 5-9 psi. i put a prefilter in front of the aux pump. but will change it for a filter which has a spin on filter when i can get one. the aux pump runs all the time, when switch is on. i can hear it when i turn the key to on position, but not when the engine is running. it will push fuel thru the oem lift pump. probably not enough for full performance, but should let me "limp" home if necessary. changed the fuel filter after new pump was in--sure makes bleeding and filling the new filter a breeze. didn' put any fuel in the filter bowl--just turned on the "prepump" and pushed in on the schrader valve at the top of the filter. air came out then bubbles then fuel. bumped the starter once to let the oem pump cycle once--hit the starter and she fired right up, missed a couple of beats, then smoothed out. i don't have my gauges in yet, do can't comment on pressures. still trying to find an electric shut off to put before the prepump-- security, engine run on,etc.

i'll post after i've run it awhile.