Engine/Transmission (1998.5 - 2002) I have new info on 24V LP issues...

[EKoster]

I have info on 24V LP issues...

My LP recently died. DC updated me with the new intank lp yesterday. I have the common 7 psi at idle, 5 psi cruising, 0 psi wot readings. I contacted my local Cummins dealer and spoke with a acquaintance that is extremely familiar with the ISB engines and the dodge truck systems. The word from Cummins:



-fuel PRESSURE is not the key anymore. It's about volume.

-The intank pump is the answer to eliminating the problems asspciated

with the carter lp

-Any VP's that were newly installed after Jan 05 are an updated pump that is

more stout

-Having run a newer VP on low fp will not damage it.

-TOO MUCH fp is a serious problem on the vp's. High fuel pressure will kill the

pump over time. ( I don't have a specific figure here, but 24psi is WAY too

much)

-The higher VOLUME of fuel helps to keep the vp cool and lubricated.



I'm not looking for any flames here, just posting what was relayed to me from a very reliable source. I feel this info should be known just because of the number of problems that everyone has had with their lp's.



Eric

 

[Gary - K7GLD]

"-fuel PRESSURE is not the key anymore. It's about volume.

-The intank pump is the answer to eliminating the problems asspciated

with the carter lp

-Any VP's that were newly installed after Jan 05 are an updated pump that is

more stout

-Having run a newer VP on low fp will not damage it.

-TOO MUCH fp is a serious problem on the vp's. High fuel pressure will kill the

pump over time. ( I don't have a specific figure here, but 24psi is WAY too

much)

-The higher VOLUME of fuel helps to keep the vp cool and lubricated. "



Most of what you posted has been known and discussed on this board many times already - hardly "new info" - and much of the rest is either false, or at least open to serious question...



You intentions are excellent - but "info" is flawed...

 

[nps]

I'm not looking for any flames here,

Eric

Nice try - but that goal didn't last long huh?





I'd like to believe everything that you say. The problem I have with new intank pump is "How can volume go up but pressure goes down?"



Think about it - all things equal in the system before and after the intank LP, the only change made with the new pump is the fuel module according to my understanding. Even the banjos stay where the LP used to go. However, in hydraulics, a given flow rate and restriction creates pressure. If flow goes up (as claimed) but pressure goes down, that means that restriction must have gone down also. What restriction? The return line in the fuel module? It has to be a restriction removed after the FP gauge, and nothing else has changed.



Run this question by your source and see what further insight you can get. Thanks for the info.

 

[Ncostello]

Every pump has a curve or range in which it performs best. For example a 1000 GPM fire pump is designed for 1000GPM at 150psi, 750GPM at 200psi, and 500GPM at 250psi. Those are just some facts that are easy to verify. If pressure keeps going higher... the flows get lower. Same for going less than 150psi. The volumes will drop as the pressure falls below 150 psi. But fire pumps are designed to run at 150 to 250 psi working pressures so thats how they get rated.



The fuel pumps Cummins chose have a operation range too. What is that range??? Who knows. Perhaps nobody really knows because perhaps it wasn't considered an important issue to study. The whole deal would involve very specific engineering analysys of the Dodge fuel line system and the Cummins VP44 system as a whole... and all the possible variable fluctuations. Then a specific set of pump specifications could be derived from the system analysys. Finally a pump meeting the design specs would be selected based upon its unique pressure and flow characteristics.



I personally don't believe there existed a large enough selection of 12V minature fuel pumps for Cummins to select from. I doubt they wanted to start making their own special electric motor fuel pump either. So they got out the Carter catalog and found a 12V pump that supposedly could handle diesel. It appeared to deliver a volume and pressure that was most likely adequate for an average situation that the pump would encounter.



However the fuel system is somewhat dynamic and a 12V motor has a tough life anyway... especially one that is run constantly.



In the end the little pump couldn't withstand the harsh environment it worked in and bypass valves failed, brushes burned out etc.



It wasn't about pressure or volume in the first place. It was about an electric motor and pump mechanism that would simply survive the conditions it was expected to live in.



You can't get pressure OR volume when the pump isn't running right or breaks.



Just my two cents after working with them plenty.

 

[EKoster]

Most of what you posted has been known and discussed on this board many times already - hardly "new info" - and much of the rest is either false, or at least open to serious question...



You intentions are excellent - but "info" is flawed...

I'm sorry Gary, just posting info, not looking to throw people off. I understand that you are very knowledgeable when it comes to the cummins and it's related parts, I was just hoping to do some clarification as it seems that many other people have/had the same info that I did in the past. I have researched the lift pump issue a little, but I have never come across most of the info that I posted above. Guess I missed it. All I was relaying was info that was given to me from who I feel is a very reliable source. Gary, please detail for me those things that are false or flawed, I don't want to post inaccurate information.

 

[rivercat]

Gary, please detail for me those things that are false or flawed, I don't want to post inaccurate information.

WELL GARY?

 

[Ram4Sam]

Tick,tick,tick,tick... .

 

[Fishin Guide]

I would say that you are relaying what you were told by DC. But, I think they tell us what they think they want. For a dealer to even use Cummins in a sentence should send up a red flag. They about as much about Cummins as they knew about that Kia they were selling last week.



You have to keep that high pressure pump fed. And low pressures have been a documented cause of failure of the VP44.



Not saying you are wrong, but zI think the dealer gave you bad info. Besides, it's an easy way to justify band-aiding this fix to customers.



JMO.



Dave

 

[Gary - K7GLD]

I have researched the lift pump issue a little, but I have never come across most of the info that I posted above. Guess I missed it. All I was relaying was info that was given to me from who I feel is a very reliable source. Gary, please detail for me those things that are false or flawed, I don't want to post inaccurate information.

My comment was intended not as criticism, only pointing out that you supplied ifo is actually pretty old stuff, discussed on this board in pretty deep detail. To give my own deductions - backed by others on this board, relative to what you posted:



"-fuel PRESSURE is not the key anymore. It's about volume.



That may be the "new" DC "standard" for warranty testing and replacement - but FEW here are about to toss their fuel pressure guages on the trash heap because of it!





-The intank pump is the answer to eliminating the problems asspciated

with the carter lp



PURE *BS*! plenty of discussion in past threads has revealed the poor flow characteristics of the DC "fix" for the Carters, PARTICULARLY if even relatively MINOR power mods are added - plus, the number of reported failures of that in-tank pump to date make it's "ultimate fix" status quite unlikely. It's NOT bulletproof!





-Any VP's that were newly installed after Jan 05 are an updated pump that is

more stout



There WERE no "newly installed" VP-44's after Jan '05 - Bosch ended production of the VP-44 about a year prior to that time, and all replacement since are rebuilts.



-Having run a newer VP on low fp will not damage it.



Highly doubtful - and who will gamble a $1200 pump to prove it?





-TOO MUCH fp is a serious problem on the vp's. High fuel pressure will kill the

pump over time. ( I don't have a specific figure here, but 24psi is WAY too

much)



No documented failure from "too high" a PSI has yet been presented here - I myself have been running 22 PSI+ on mine since the truck was new - but your source may be right - another 300K miles and 15 years or so MIGHT eventually do it in! :-laf :-laf



Note the lower guage fuel PSI in the pic below:



#ad




-The higher VOLUME of fuel helps to keep the vp cool and lubricated. "



THERE - the ONE purely and undisputed TRUE statement of the lot! :-laf



There, hope that covers it - most of the above are NOT just my personal opinions, but based upon the opinions and real life experiences of a number of other members here.



Cheers...

 

[nps]

So what part about "Cummins Dealer" in the original post don't you guys understand? What vested interest does a Cummins shop have in defending DC? And how about all the cases of good/high FP combined with love and care, and the VP still crapped out? Hohn and Rweis are two that come to mind.



I'd like to find out if this info source has some new data rather than just shutting it down over emotional bias.



And Gary - I'm sure there have been many 'newly installed' VP44s since Jan 05. Heck, think there were at least 3 or 4 threads about new VPs this week. :-laf He never said they were new VPs, just *NEWLY INSTALLED*.

 

[EKoster]

Maybe I should clarify... All of the info that I was given was NOT by someone at a DC dealer. The info came from a shop in the stockton area that sells cummins parts and works on cummins engines. They are in no way associated with DC in any way. The guy I spoke with works specifically on the ISB engines and has day-to-day experience with our engines, and ram pickups and has contacts directly with cummins. I guess in this world, that still doesn't mean that it's credible though...



Eric

 

[Gary - K7GLD]

"I guess in this world, that still doesn't mean that it's credible though... "



Eric, no need to go on the defensive, or appear to be under attack - fact is, YOUR "credible" info must be carefully weighed aganst OTHER equally credible sources - and SEVERAL of mine come direct from Bosch reps and their authorized service reps - which *I* will take over a Cummins rep most of the time, at least where Bosch pumps are concerned!



Even at THAT, on some issues, even info from Bosch reps tend to contradict each other...



Here's one of this board's more elaborate related threads - you may have missed it:



https://www.turbodieselregister.com/forums/showthread.php?t=137029&highlight=lift+pump



and another:



https://www.turbodieselregister.com/forums/showthread.php?t=143179&highlight=lift+pump



And another:



https://www.turbodieselregister.com/forums/showthread.php?t=139263



And here's a sample quote:



"Just got a fuel guage installed to check pressures on the new in-tank pump.

BAD NEWS! Idle pressure is about 7psi. It runs down the road at about 4psi and WOT will suck it down close to zero. I can't believe the VP44 will survive for long with the pressures this low.

I'm back to debating whether to just sell the truck or try putting the old LP back on and hope the tank pump can keep it going. I would think the two pumps working in series can keep the fuel pressure up there. As nobody's done it yet this is just speculation.

I will call the dealer that did the install and see if they're having any complaints so far. They told me they've done quite a few new installs to date and they thought it was the solution to the LP problems. I wonder if they really no what kind of pressure this thing puts out or if they just like the idea of an in-tank pusher pump.

Anyway, I don't like the looks of this fuel pressure. If the pump gets weak with age (like the oem LP) you could cook the VP in no time.

Mike"



The basic fact of this thread remains, you came here sorta breathless and wide-eyed thinking you maybe had new revelations about our fuel systems - good for you for trying to share, it just happened your info was neither new, or totally accurate - at least in the eyes of others here...



Thanks for trying - you're among friends here, and who knows, your next revelation might be a home run!

 

[obert]

It was about an electric motor and pump mechanism that would simply survive the conditions it was expected to live in.



You can't get pressure OR volume when the pump isn't running right or breaks.

I have lost one VP and three carter lp's. The two lp's after war. I put on myself, and disected the old ones. The vane pump itself was fine, but the plastic drive hub sheared off. The motor on the last one was even still good.



Im just a lowly mechanic and I see what I see. I take info from the guy in the nice shirt that comes in once a month with a briefcase and laptop full of warraty claims with a grain of salt. No offence to DSM's, and mine is a real good guy/ very knowledgable.



with my experience the catrer does fine, IF it doesn't take a dump for no apparent reason. Sure, big bombs might need more, but I'm not there..... yet Oo.

 

[rweis]

I still vote mechanical RASP for the lp function. You can adjust it to whatever psi you want. Long term fix. Even uses the OEM lp as a backup.



Bob Weis

 

[Supermod56]

I still vote mechanical RASP for the lp function. You can adjust it to whatever psi you want. Long term fix. Even uses the OEM lp as a backup.



Bob Weis

I second that, great system, the harder you mash the gas, the more volume you get. It was never a question for me on which one to get

 

[cyborg]

Every pump has a curve or range in which it performs best. For example a 1000 GPM fire pump is designed for 1000GPM at 150psi, 750GPM at 200psi, and 500GPM at 250psi. Those are just some facts that are easy to verify. If pressure keeps going higher... the flows get lower. Same for going less than 150psi. The volumes will drop as the pressure falls below 150 psi. But fire pumps are designed to run at 150 to 250 psi working pressures so thats how they get rated. .

Well not exactly. All things being equal pressure and flow go up together. At higher flows you need to increase pressure exponentionally (sp) to overcome friction loss. The difference between the 150. psi (capacity test) and the 250 psi (pressure test) are the difference between a pump operating in series or parallel. Thats wye (why, pun) we have to choke or gate the discharges to make the pressure go up and the flow go down. To make the pump work harder. I think a better analogy would be the overload test, where the pump operates at maximum flow, pressure and rpm, to the point of diminishing returns. The point where more rpms provides no gains.



I wish I knew the numbers to figure the difference between 1/2" and 7/16"? The in-tank-pump MIGHT be an improvement, but they minimized it by adding a restriction (FL) in the form of the fuel block that replaces the stock LP.



My answer will be adding a pump at the stock LP location and a big line kit.

Kind of like going from 2 1/2" to 3" and tossing in mutual aid (a second engine) for the long lay. Both pumps work less



You are right the principles, problems and solutions are the same. The Carter pump is not up to the job. A lot of band-aids to cure DCs mistake.



If this comes across as a flame, I apologize in advance. It is not meant to be, in any way, shape or form.

 

[Ncostello]

Cyborg, I stand corrected. Your pump overload analogy is more correct and easier to understand.

 

[Gary - K7GLD]

The only theoretical criticism I might question the Carters for, is the use of the same (apparently) identical pump motor and related hardware on ALL PSI versions of their pumps.



This would seemingly mean the lower PSI versions, 4600, etc. , are well BELOW their failure threshold, or else the 4601 types are right AT failure.



This might be why adding the 4600 pushers is so effective, spreads the stress load across 2 pumps, instead of just one. .



Just a theory...

 

[CFAR]

Everyone covered this pretty well but...



If my stock lp produces 15psi and the new pump 7psi both through virtually the same fuel lines, then the new 7psi lift pump has less volume, period.



Sorry to see you leave California Gary, but I'm happy for you.

 

[EKoster]

okay then, what would you guys recommend for an aux. pump? Any thoughts on using a FASS vs. a RASP?



Gary - If you're ever back in Lodi and need parts or a place to work on your truck, I've got a shop in stockton, and the local cummins dealer isn't very far from me.



Eric