Engine/Transmission (1998.5 - 2002) Lift Pump Comments

[Lube Man]

The service manual says the lift pump should put out 14 PSI at idle. There are no specs for higher speeds or loads.



I just put a FP guage on the clean side of my fuel filter. Got 13 lbs. at idle. Just what you would want after the filter. Then I went for a test drive and noticed that if I put the metal to the floor on a hill the pressure went to almost zero. This got me a little concerned until I reviewed TDR postings that stated the VP44 injection pump has a built in fuel pump. If this is so I would expect that pump to start sucking harder as speed was increased. This would effectively reduce pressure at my new gauge and is why there would be no specs for fuel pressure at the outlet of the LP pump under load.



Is this a fair analysis or am I missing something here?

 

[JPLB22]

FP requirements are a matter of opinion, basicly whatever you are comfortable with. Personally I don't want to see anything under 10 psi on the freeway, and nothing under 8 psi WOT unloaded. I think pretty much anyone would recomend a new pump if you are seeing pressures at or near zero at any time.



I don't think there is anything official on the requirements of the VP44 for a good FP for healthy opperation.



Jeff

 

[Steve St.Laurent]

At one time Dodge's spec was to see nothing less than 10 psi from the lift pump at any time, they revised that to 8 psi. Now their test is based on volume. Personally I'd go by the 8 psi value and if it was less than that I'd replace it. I don't have my manual right here but I'd swear that there was something in there about what the pump should never go under - I believe it was 10 psi.

 

[Gary - K7GLD]

With a stock truck, zero PSI under ANY circumstance is not right! Even with my single stock LP and a Comp on 5x5, pulling our 5er up a steep grade wouldn't drop under 8 PSI or so - idle PSI was 15 PSI - all readings taken right at the VP-44...

 

[mediccummin]

At the festival in the foothills here in so cal, John holmes stated the VP 44 needs 14psi at idle.

 

[EBoyts]

My understanding is that the Bosch VP44 injector pump depends, in part, on positive pressure from the transfer pump for its internal lubrication-- and that driving for extended periods without adequate fuel line pressure can decrease the life of the VP44. A mechanic from Rocky Mountain Cummins told me the pre-injector pump pressure should be between 10-15 lbs during operation. It seems to me that whatever we can do to keep input pressure at the higher end of the recommended range can only be good for that expensive-to-replace VP44.

 

[GW01]

lift pump pressure

i have a 99 3500 stock with a westec fuel pressure gage. from day one of installing the pressure gage i only had 8 psi at idle. several weeks ago it dropped to 5 psi. thinking i had a bad pump i took the truck to the good old dodge dealer. theychecked the pump and advised it was ok [at this time]. i was also advised that they no longer test pressure but volume of fuel in ozs. 45 oz is within specs,mine flowed 50 ozs.

 

[mediccummin]

I wouldnt take any dealers word, that the LP is ok at that pressure. Your VP needs 14psi, This was advised to our local chapter at the foothill event by the guys that build these things.

 

[JLittle]

lift pump ?S

guys I have a 2 k dually and have drove it 1K miles in the past month, so since you guys say that a fuel pres gauge is really needed today I bought a fuel pressure gauge and mounted it inside the cab, its a manual gauge and and runs to the filter banjo fitting, I started up the truck and it showed 0 psi, truck has been running fine! I ran truck some more and it quit? I cracked open inj lines 1 3 4 and got no fuel, I then took filter top off and its half way full, I bumped starter over and made LP run and it does not pump any more but runs? now I cant run truck until I get another pump? im glad I tested the lp! how much fuel Press is too much? In my extra stash of parts I have a external mounted Bosche Porsche 911 Fuel Inj pump that I can install inside frame rail and it puts out around 30 -35 psi, is this too much pressure for the vp44? or will it regulate it down to 20 psi or so? thanks for reading this post!

 

[rweis]

I regulate my lp to 12psi pre filter and generally get 11 - 12 psi post filter.



I want to watch the torque on the lp (it's ability to push fuel through the ff). I think that will tell when to change the lp. If my VP gets less than 10 then I will change the lp.



I regulate my lp to stabilize the system pressure and keep the lp check valve closed (high failure point), also continuously filters the tank fuel through a RACOR 690 10 micron filter (pre lp).



37k so far



my . 02



Bob Weis

 

[GKarpen]

JLittle: In November of '03 I installed a mechanical pressure guage and it read zero. I thought the guage was defective. In April of '04 I replaced my lift pump with a FASS after reading about all of the LP failures. Bingo; I have fuel pressure and the guage came to life. During the six month period the truck started and ran fine running off of the VP44 only. I later found on the old pump after disassembly that the internal check valve was frozen tight. The pump ran but nothing was coming out and the impellers were fine This pump is junk. In other words; without the fuel pressure guage I would never have noticed that this pump did not work until it was too late and the VP44 failed. The FASS you can regulate by changing a spring. I have a Westach electric and a Di-Pricol mechanical installed. They are one pound apart. I read around 14 Psi consistently.

 

[EBoyts]

Just chiming in after reading the above post-- for what its worth, I also switched over to a FASS and get a steady 14-15 lbs no matter how I'm driving. After driving with the LP-- which made the guage read somewhat erratically between 5 and 13 lbs-- I get a real satisfaction looking down and seeing that needle rock-steady on 14. For me, the added peace of mind is worth it: I have greater confidence in my truck. I wish the folks at D/C would spec something more along these lines to begin with. With their economies of scale, it might only add a few hundred dollars to the sticker price-- and these already bad-*ss trucks would be even better (not to mention what would happen to customer satisfaction). Oh, well.