Engine/Transmission (1998.5 - 2002) I suspect a lot of money has been wasted on Lift Pumps

[rweis]

Nice, Gary, well put.



Bob Weis

 

[mediccummin]

Well put Gary. I think the research he is referring to was a phone call to cummins and that was the extent of it. If you research the TDR which is a wealth of info on the this subject there is much more input than the fact that a LP is not needed. I think before you bring out a theory and bang it around you should have some info to back it up first. No name calling here :{

 

[Jar Head]

stock truck

Because of the TDR I finally broke down and bought a temp fuel gauge.

14. 5 idle

14 cruise

10 WOT up a 6% from a roll

WOT from stop at bottom of same hill 5 then climbs to 10 and holds

I'm just under 82,000 on stock pump. Truck remains as delivered from the dealer. Truck is worked hard. I sleep fine.

 

[fj40charles]

Lubeman wrote...



Sometimes a little extra knowledge is not good unless the knowledge is understood. Most owners do not have FP gauges and drive around ignorant of fuel pressure. Then they go out and install one and right away go into a panic over readings that they do not fully understand. Instinct would indicate that pressure should increase with engine speed just like oil pressure. But that is not the case here.



=========================================================

It is still better to have some way of monitoring fuel pressure than driving blind. If you do a search on lift pumps, you'll find thousands of posts.



BTW, I've got a carter pusher pump and I have not had a lift pump failure in over 2 years. My first 2 lift pumps lasted less that 2 years (combined).

 

[Lube Man]

Well it's always gratifying to introduce a thread and see it take off. Indicates a subject of interest and that people are thinking.



As an engineer I try not to postulate theory. That's for the philosphers and theoretical physicists. I made some comments at the beginning of this thread as to my anaylsis of how the LP system functions. My analysis is in keeping with the 1999 Dodge Service Manual. I came back with another comment after talking with Cummins and gave the Cummins number if anyone wanted to pusue the issue directly with those who designed and built the engine.



I appreciate all the comments, both positive and negative. I do note that no one has really taken issue with my analysis of how the system operates.



I don't feel I can contribute further to this thread. I am satisfied with the operation of my LP. I don't feel it will accomplish anything to get into personal arguments. Again, I urge those interested in pursuing the discussion to contact Bosch, Cummins, or Dodge and get better informed.

 

[Murle]

Well I don't even have a LP any more. I have a FASS and all my worrys are gone about having a bad LP. . I looked all all the posters here and noticed that only one showed to have a FASS installed. It is worth the piece of mind not to worry about having the LP to go out on me.

 

[Bandit2]

Looks as if Lube Man opened up a can of worms. I thought it was educational!! WE get old too quick and smart to slow.

 

[Steve St.Laurent]

Again, I urge those interested in pursuing the discussion to contact Bosch, Cummins, or Dodge and get better informed.

I have sat and had dinner with them. I've also had a personal tour through Cummins engineering and test facility in Columbus and spoken with one of the head guys that developed the 24v in the early 90's. I've also talked with one of the head people at Dodge who was dealing with the replacement of lift pumps and that wrote the guidelines back around 99 to replace any lift pump that was producing less than 8 psi. I've also had a Bosch engineer that did the tech talk at the TDR nationals in my truck personally taking him for a test/joy ride and talked it over with him. In short - I HAVE talked with them, and lots of em and I'm quite sure that ALL of them were not wrong. I also know for a fact that on my own truck when I saw my lift pump get to a point where it was sucking it down to 0 psi that I had a performance problem - which would be fixed immediately with a replacement pump. I also know that I replaced 4 lift pumps that went to 0 psi in less than 40,000 miles and had a noticeable performance problem 3 of those 4 times and that I then put a pusher pump on in addition to my stock pump (in series) and have not seen pressure below 16 psi since that time (90,000 miles later) and have not replaced another pump nor had a performance problem - NO other changes to the fuel system in any way.



Just my personal experience.

 

[Lunkerman]

After determining my LP was dead while changing my fuel filter Sat. , I headed for the dealer today to drop my truck off for LP replacement. I figured hey--this is great--I'm gonna get a new pump, N/C under warranty. FREE is good! Not so Quick!!

I get a call around 11am, "Your truck seems to be running fine,can you give us a little more info as to exactly what problem you were experiencing?" Mind you they knew EXACTLY why I was coming in. I explained the scenario again about the filter change and the LP not pumping up my canister Yada Yada Yada. They said they would pass the info on to the mechanic. Why couldn't the mechanic call me himself? I get a call about 3PM saying my truck is ready because they couldn't find anything wrong with my LP!! To make a long story short, they said the truck wouldn't run if the LP was bad, the computer controls the pump and there was no error codes! The truck runs fine!

Do you think I'll ever buy a vehicle from that dealer? I wouldn't let them change my wiper blades! Luckily my friend works there as a car mechanic and he's bringing home a new LP for me N/C. We'll do the 15min. install and be done with it. I'll buy him a couple cases of Adult Beverages!



John

 

[rblomquist]

Gary, I understand what you're saying and I agree about many of the things we all go by as gospel on the boards but there *can* be more than 1 side to a coin, that's all I'm trying to say. I welcome new information, I'm big enough to read it, and if needed do my own research and decide if it's valid or not.



Maybe, if everything that is to be known about LPs has already been cast in stone then we should disallow any more active posts on them and just have folks use the search function or make a short list of LP facts (and be done with it). I prefer to read new "takes" on stuff though.....



BTW, I never said or implied in my last post the following things you posted back on i. e. I never implied that we have to take someone's theory (or post) as cast in stone nor did I say we should take a course of action because (in this case) Lubeman talked to 1 Bosch or Cummins employee. That wouldn't be logical. .



Everyone has their own perceptions. I would say if someone said in-the-blind (no refernces to back up their statement) that "we should run without any kind of fuel pump" I'd say that was *radical*. But I don't think that someone who posts something like "running at 6 psi is safe for our VP44s per Cummins regional technical guru Joe Schmo" should be called radical and shunned off the board. Of course, it's totally cool to question the heck out of the claim and the source's credibility but I'd still rather have the opportunity to listen and watch a back and forth logic basic discussion.





There's a lot of people on the board that knee-jerk with the attitude that there's only X-way to do [fill in the blank i. e. LPs, Pyros, trans fluid, etc] I'd rather see alternate ideas backed up with some kind of real world or credible source; then let the reader decide. I guess I'm just concerned that we're getting more and more of a stovepipe vision and anyone that dares to post another way, theory, or idea will get immediately beat down, called crazy, or worse.



No hard feelings, just voicing a concern.



Rich

 

[JoshPeters]

Just reading along here and enjoying. First off I'm a 12valver. I'm learning. What LubeMan is saying makes sense to me. Let me see if I'm interpeting it right: The VP doesn't need the LP. The LP is ASSISTING it by getting the fuel to it. Now, if you took the LP out, the VP COULD theoretically run just fine without it. Now when the LP dies, it has become a Restriction in that line causing the VP to NOT get the fuel it needs. Hence, Death. Now I understand that no one will try this but think about it. Remove the LP, put LARGER line in on the suction side. Not just from the tank, in the tank right up to the inlet of the VP. Now there is more than enough reserve for the VP to feed off of. I've seen a FASS installed. I noticed that the lines were much bigger. Why? If pressure is pressure, why don't they use much smaller line. Because you can't move enough fuel within that small of a space. A stock truck with no LP, just lines may survive. (I'm guessing/theorizing)



The reason I see the LP being on our trucks is this: Fuel filter. Change it. Now how do you prime the system. What if it gets dirty. The VP may be able to run with out the LP, but not with a dirty filter.



Well guys, Tell me if I should keep my mouth shut and stick to the 12 valve forum!

This beats the heck out of watching TV anyday!

Josh

 

[jarsong]

Lift Pump

I sort of agree with Lube man on this. A few things have never made much sense to me. Number 1, most NEVER, really MOST never have a problem with the lift pump/VP44. Number two, SOme that have actually broken the lift pump have multiple failures. Seem to me for this to happen there is a third factor here we haven't pinned down. My guess is dirty contaminated fuel. Having said that there will always be a certian number of pumps that just fail like altenators or anything else, SOME of these will take the VP44 with them if flow is restricted to much from the failure.

jarsong

 

[Ramtough]

Don't know whether to continue here or start a new thread. IMHO, I have a failing LP. I have 4-5# of pressure @ idle, 2-3 @ 70 MPH & 0 @ WOT. The current LP (my second) was installed @ 62K MI. I am now @ 76k. Took the truck to the DLR last wk & they performed 2 flow tests. They say the truck exceeds the factory output of 45 oz in 10 seconds. They say that "THERE ARE NO PRESSURE SPECIFICATIONS" for the LP or the VP44. From my research here, I understand that Dodge withdrew their pressure specification. I have seen a lot of discussion RE what Bosch engineers are/have said. I have not found one single reference to an official specification or formal announcement from Bosch. Why? This is not rocket science. These stories are not admisable in court. Where is the proof? If I have a VP44 failure out of warranty and I have known that the LP was bad for a long time, how can I go after Dodge?



FYI - I ordered a F. A. S. S. last week for my own piece of mind. I am confident based on what I have read here that it will solve my problem. I just wish that it was possible to find more facts here than opinions.

 

[Coyote556]

Some vp44's just fail also, with no apparent related lift pump issues. I have 63k miles on my truck right now. Bought it with 30k on it. I have been checking LP pressures at every oil change since I bought it. Never below 14-15 psi at idle. Now my vp44 has gone south for the winter. WHY? Who knows? If you know, please tell me. I sure wish I knew. But I have the dead pedal and the code 0216 to match and my original lift pump is still trucking right along at 15psi. Go figure.

 

[Chugiak]

Ramtough, take your truck to your local Cummins distributor if they're nearby. They are well familiar with the problems encountered with the lift pumps and VP44's. While the lift pump fails way too often, ignoring a filing lift pump almost certainly WILL cause the injection pump to fail. Whether it's debris from the lift pump going downstream to take out the injection pump, or the injection pump having to work too hard at idle, we see way too many folks come in and buy an injection pump that maybe could have avoided it if they had monitored their fuel pressure along the way. Just my two cents.



Cheers,



JPH

 

[rweis]

VP



What about heat on the VP circuit board?, what about lubricity with the LSF?, what about free water passing through the OEM filter?, wire tapped?, full flow fuel lines?, ... ...



LP



electrical connections?, check valve failure?, vanes not fully extending?, motor nylon connector stripped?, motor failure?, motor not producing torque?,



Just some ideas off the top of my head, I'm sure there are many others.



Bob Weis

 

[Gary - K7GLD]

I've been aware for some time of the tendency of the LP to cavitate as restriction - on either the intake or output side reduces flow.



And as the lead post points out, the greatest pressure seen by the LP is at low demand, such as when the engine is idling. On a test I did involving a stock LP, once cavitation was established, the only way normal fuel flow could be regained was to shut the LP down completely and restart it.



I'm currently having some LP cavitation problems of my own, due to an excessive percentage of engine oil I have in my fuel (don't ask! ), and the only thing saving my hide is my added Carter pusher pump that literally FORCES fuel thru the cavitating stock LP, motivating a return to normal fuel flow once fuel demand is increased as engine load increases.



A plugged fuel filter, or in-tank filter screen can easily encourage LP cavitation, even though the pump APPEARS to be functioning properly.

 

[Morphious]

I'll give you guys my experience over the last few years (now that I'm thinking about it, it's more like 4 years) with my truck. I removed the stock lift pump with 36k miles on it and put in a Mallory 4140 (140gph) fuel pump back by the tank. I wired it to a relay that was switched by the stock fuel pump wires. I ran -6am lines from the pump to the filter and then on to the injection pump. About every 6 months, I would burn the brushes out of my pump, and would have to rebuild it. Not a big deal, other than a diesel bath and 15. 00 on brushes. I kept a spare set in the glovebox after the first one went out. Did this scenario for a couple of years.



Then I was in the mountains of North Carolina late at night on the way to Knoxville for vacation 2 summers ago and it went out on me. I didn't have a spare due to the parts store screwing up the order and not getting any in before I left. I ended up pulling the guts out of my pump and using the injection pump to suck fuel through the housing, made it to my destination fine, and picked up another set of brushes the next day and rebuilt the pump in the hotel parking lot.



I have had this happen twice more, and performed the same until I could pull the pump and rebuild it. I can pull the guts out without removing the pump.



I had a relay go bad on me about a year ago, and didn't have a spare one, so I just routed power to the pump (I already had a kill switch in the cab of the truck to break the circuit). Since that time I have not had to rebuild the fuel pump and it is still putting out a steady 12psi at idle.



The truck currently has 190,000+ official miles on it as of last week, still running the stock injection pump. Here is my synopsis, the truck can run fine without the fuel pump, but it must be obstruction free. I had to pull the guts out of my pump in order for the truck to run (but that is the design of my pump, it's a gerator style, so flow when off is almost nil).



Second the powering of the pump or switching it on by the computer controlled wires may be another culprit of the pumps lack of longevity. If I rmember right, the comptuer cycles the pump in some way to ensure proper fueling pressures. I just get in the truck flip the fuel pump on and crank it. No hard starts, no problems.



I am still running the same Mallory Fuel pump I bought sometime in 2001. I bought a second one, but ruined it out here in SC due to getting into some deep saltwater one night downtown when the water levels were real high.



Morph.

 

[Allnew2Me]

Perfect timing, I just this weekend changed my fuel filter because when I bought the truck last December it had been supposedly changed. I ignored the shop manual method of filling the fuel filter canister with clean fuel before inserting the new filter and instead went with the other method. I clicked but did not start the engine and let the lift pump run until it stopped. The first time it ran for about 20 seconds, the second time about the same and then the third time it ran for about 10 and stopped. when I tried to start the truck I got a quick start and then it died, nothing. Crank crank crank and still nothing. So then I removed the fuel filter again and filled the canister with fuel. Then I loosened the banjo at the VP per the shop manual bleeding method and ran the lift again until fuel was present. tightened the fitting and after only about 10 seconds of cranking it started right up. My question is this, because my lift pump did not fill the canister does this mean that it is dead or is there possibly some other reason perhaps like air compression in the system? It seems to me that if the pump is running, I can hear it, that it is pumping. It is supposed to be self-priming of course but with air ahead of it will it still fill the fuel canister or just push against the bubble? I have a feeling that the LP will certainly self-prime but if the output is restricted, even by air, it may not fill the fuel filter, hence the manual method of bleeding the air out.

 

[rweis]

From Gary's post about cavitation I wonder if the bypass filter on mine prevents that? Anything over 12 psi is bypassed to the tank and therefore the lp output has an alternate place to go other than the VP. Theoretically the fuel should be moving all the time through the lp. If high demand then to the Vp with little bypass, if low demand then little to the Vp and a lot to the bypass.



No cavitation was not my objective with the bypass regulator, but it may be a good by product of dumb luck. Oo.



Bob Weis