Engine/Transmission (1998.5 - 2002) Lift pump pressure question

[RANDUCCI]

I wanted to know if any one else has had this experience with their lift pump. The normal running pressure is between 2 to 3psi, 4psi when backed off of the throttle (like slowing down or going down hill). If I hit WOT it goes to 0psi then jumps to 11psi until the high demand is gone, then back to the 2 to 3psi normal reading. I have installed 3/8 lines with AN fitting so there is less restriction than normal. I have also a Edge EZ box installed. The truck seems to have great power, 212 rear wheel H. P. on dyno without the Edge EZ box. There doesn't seem to be any performance problems now but I don't want to harm the VP44. Should I try a Aux. pump back by the fuel tank first or replace the lift pump and see what happens? What is the part number of the replacement pump that Cummins sells? Thanks in advance

 

[mikel]

You are going to want to do something about those pressures, going to 0 psi is bad news from everything I've heard. I have heard at least two views on the pressure issue, one side said that as long as you have positive pressure (even 1 or 2 psi) at all times you are ok, the other side says you need a minimum of 8 psi to allow for enough extra fuel to cool the vp-44. I'll tell you that I did what I had to in order to never drop below 8 psi on my truck.



Good luck,

Mike

 

[WadePatton]

EGGzacktly why you have a FP gauge.



Get a new LP from Cummins today!

 

[noland]

The part number is 3990105.

 

[High Voltage]

I think it's way gone... ... Time for a new one, Don't buy it from the dealer. .



I run 16 psi at idle and 9 WOT... .

 

[andrewkoperdak]

If you are certain there is no air in your pressure line ... . then you have a bad lift pump. Let DC buy you a cup of coffee and a lift pump for Xmas. My pump crapped out with less than 10K miles on it. new pump gets 14-16 psi at 60 mph and pegs my meter at idle. I never see less than 12 psi.

r,

Andy

 

[OL RATLR]

Lift Pump

Don't walk. Run and get a new Lift pump before you

have to replace the VP 44. :{

 

[RANDUCCI]

Update

I went to my local Cummins dealer to get a new lift pump but I thought that I would talk to someone in the service department first. They guy at the counter called the Tech line and had me talk to one of the technical help personnel. First I should mention that my gauge is located after the fuel filter and before the VP44. The Cummins Technician gave me a lot information, so I will boil it down. Since I was taking my reading after the fuel filter he said that the 3psi was normal when the engine wasn't demanding much and that when I stepped down on the throttle, there was a lowering of pressure until the lift pump could sense a greater need and catch up to the 11psi reading that I was seeing. He said that if I took my reading at the inlet of the fuel filter, I should see 9 to 10psi. Since I have 3/8 lines with AN fittings, it will be easy to make this switch. I'll try this first before buying a new pump.

 

[cD'amato]

Price

How much is a new lift pump? Im confused I thought the VP44 was the lift pump. I made a mistake on my thread earlier. Well. directly from the folks at Cummins earlier today...



With the engine off and the pump running OR cranking to start the engine, the PSI should NOT be below 6 PSI.



While driving under any load conditions the PSI should NEVER be below 10 PSI. Where did I see that gauge that is temporary that people were raving about to test the lift pump?

 

[WadePatton]

A new LP from Cummins was 145 with tax for me.



Forget cranking and any other pressure reading except at BOOST under LOAD. That's when they'll go low, if they're going to. But stop whenever you see "0" psi. Us BOMBER's are happy with any positive pressure at BOOST under LOAD, depending on how many ponies are being produced.



Briar Hopper is the gauge. Call Black Mountain Diesel in KY or borrow one from a nearby member. They should be part of the "new member package" for 24v folk.



BMD site down for reworking. Call 'em at 859-234-3111

 

[drifter]

Got my gage from Geno's. The sender is mounted in the output side of my fuel filter (between the filter and pump). Truck is a 99 with 48,000 miles. Reading never goes to zero!

At idel it maintains 10 - 12 PSI, WOT 7- 8 PSI. If I were going to ZERO or seen readings of 2 or 3 PSI I would be putting a new lift pump on.

With the readings that I have after the holidays I am giveing some concideration to replaceing mine with a new one and bagging my existing pump for a "emergency spare".

My pump has held these pressures for a long time and I read them as "normal" for me. I have never compared the inlet / outlet pressure differance but I give it at least 1 or 2 PSI more on the inlet side. I change my fuel filter every spring and drain for water

every other tankful or so, more thoughtful of this during winter and high moister conditions. I use Lucas fuel conditioner most of the time (about 8 oz every tank full). I drive until I get my low fuel warning and put in about 27 gal. in.

 

[Ron Bissett]

Re: Update

Originally posted by RANDUCCI

I went to my local Cummins dealer to get a new lift pump but I thought that I would talk to someone in the service department first. They guy at the counter called the Tech line and had me talk to one of the technical help personnel. First I should mention that my gauge is located after the fuel filter and before the VP44. The Cummins Technician gave me a lot information, so I will boil it down. Since I was taking my reading after the fuel filter he said that the 3psi was normal when the engine wasn't demanding much and that when I stepped down on the throttle, there was a lowering of pressure until the lift pump could sense a greater need and catch up to the 11psi reading that I was seeing. He said that if I took my reading at the inlet of the fuel filter, I should see 9 to 10psi. Since I have 3/8 lines with AN fittings, it will be easy to make this switch. I'll try this first before buying a new pump.

If that tech is correct then I am a Chinese Aviator he is blowing smoke up your tail pipe . After the filter is the place to check as that is what the injector pump will see . Take it to a different shop DC has some good shops and bad you seem to have found one . I can not see why any one would not get a pump from DC under the warranty the same one from Cummins goes for 139 to 179 $ depending how greedy the place is . Same pump different number on it DC ends in AA second mod and Cummins 105 . Ron in Louisville :-{}

 

[cD'amato]

Heh Im laughing at the Chinese Aviator comment still! Funny thing... . I think I need a new lift pump and the stealer tells me that its only covered under my 3yr/36000 mile warranty since it is not an "internal" engine part. So I'll have to shell out the money out of pocket I guess.

 

[WadePatton]

Originally posted by cD'amato

Funny thing... . I think I need a new lift pump and the stealer tells me that its only covered under my 3yr/36000 mile warranty since it is not an "internal" engine part. So I'll have to shell out the money out of pocket I guess.

Try a different stealer--if you really want those folks under your hood. When I told the SM at the dealer who did my reflash that I had replaced the LP at 55,000 miles he said "that should have been warranty work. "



and I agree with the Chinese Aviator comment.

 

[RANDUCCI]

Final update

After placing the fuel pressure pickup point inbetween the lift pump and the filter the pressures were still varing between 3 to 4psi at times and 11 to 12psi. I stopped at the Cummins dealer on the way home and installed the new lift pump. The new pump has reading of 14 to 15psi normal running and 10 to 11psi under load. Even though there were no real symptoms of a power problem, the lift pump was going bad, I guess that is why we install gauges. Thanks for the help.