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

[Gary - K7GLD]

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

Thanks Eric - thought I was gonna need something like that a week or so back, when I lost almost all my fuel pressure. I carry a full set of replacement pumps, including the VP-44 - but I got lucky, and it was just the power plug to the stock LP that had come loose...



And as far as various aftermarket pumps, from what I see/hear, the RASP looks like the most reliable...

 

[supeerman4422]

the more and more i read, the more and more i love my 12V

 

[Gary - K7GLD]

the more and more i read, the more and more i love my 12V

Well, there ARE trade-offs - the 24 valvers are capable of on-the-fly timing and fueling changes, delivering both economy AND power on instant demand the earlier purely mechanical fuel systems can only DREAM of...



As to the above mentioned LP threats and weaknesses, THOSE are easily cured by any of several replacement LP setups available...



It cost me about $2000 to get the same power gains with my '91 12 valver that I got for well under $600 on my '02.



Is the use of the 24 valve style LP a significant reason to avoid that engine?



Not for me.



Would I still buy a 24 valve truck, even with LP issues?



YOU BETCHA! :-laf

 

[CFAR]

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

Whats wrong with using the stock lp in the stock location? You have the pusher pump in the tank. With the two of them working in tandem you should have pretty good pressure/flow. Don't know what situation would develop if one or the other died though.

 

[Bob4x4]

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

As long as you don't do a hard face plant in the dunes with a sport pkged truck

 

[Bob4x4]

Whats wrong with using the stock lp in the stock location? You have the pusher pump in the tank. With the two of them working in tandem you should have pretty good pressure/flow. Don't know what situation would develop if one or the other died though.

If either pump fails it will become a BIG restriction and you will have less flow than either pump on its own .



Bob

 

[Ncostello]

I'd personally go with some version of a OEM Cummins mechanical pump. Of course that means switching cams... but I guess it would be worth the extra work in the long run. Question I have is... if you remove the OEM pump and leave its harness plug hanging... what kind of codes does the ECM set if it doesn't "see" the motor there?



Cause if I were going to spend the dough to go with a Rasp or a new cam... the electric would be out and I"d have to find a hand primer setup.

 

[steved]

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

Now I have a question... the VP-44 has a 14psi pressure relief built internally... is that before or after the internal LP?? If it is before, then you really would be just returning everything above 14psi back to the tank right?



steved

 

[Hohn]

Don't be too put off by those folks here who are pretty jaded about someone coming in with "new" info on the LP problem.



The fact is, at least a thousand posts on this board have discussed the 24V LP problem in very great detail.



It's not that there are "know it all" types, it's more that we've pretty much left NO stone unturned over the last 6+ years.



Gary and the others aren't trying to be rude (though it may seem); rather, they are just pretty jaded from having beat this subject to death in every conceivable form.



Truth is, we have no idea what causes VP failures, or why the LPs don't seem to last. Some have had them go a long time. Other have had a lot of problems.



As mentioned, I personally lost a VP with good FP the whole time, and NO WIRE TAP! I "did it all right", according to prevailing TDR wisdom (good FP, got a guage, didn't tap the wire, opened up the restrictive OEM fuel lines, etc), YET I STILL LOST A VP.



By the way, more pressure doesn't always equal more flow. Sometimes is means less, depending on whether you are measuring deadhead pressure (static) or dynamic (moving). More pressure can CAUSE more flow, and lower pressure can be an INDICATOR of more flow.

 

[Hohn]

Now I have a question... the VP-44 has a 14psi pressure relief built internally... is that before or after the internal LP?? If it is before, then you really would be just returning everything above 14psi back to the tank right?



steved

I'm not sure if it's before or after (I believe it is after). I believe it would be more accurate to say that the VP is TRYING to return all fuel above 14psi, but can't because it flows to poorly.



jh

 

[Fishin Guide]

Ncostello, the code you get os a 0230. This can be overcome with a small gauge light or a resisitor plugged into the harness. I have not done either.



Hohn, I believ that the answer is the overflow valve would be after any internal vane. I took the overflow out all together to try to get a lower fuel pressure with my pump and still had well over 30 psi.



The VPs internals are just much more restrictive than the old 12V injector pumps.



Dave

 

[mhenon]

If either pump fails it will become a BIG restriction and you will have less flow than either pump on its own .



Bob

Bob... do you know that for a fact? What do we know about that in-tank pump? Who makes it... . what kind of pump is it... has it been used in gasser applications or is this something designed for diesel fuel only... . if it stops (fails) does it become a restriction or will the VP suck fuel through it???

This info may have been posted already (I've been on the road for awhile) but I don't know squat about this pump.

I did gripe to the dealer that installed mine. They weren't happy with the fuel pressures either but apparently DC is. Here's a little update on my pump with about 5K miles on it.

It's seems very sensitive to fuel system conditions. I just changed out the fuel filter and picked up about 1 to 1 1/2 psi. Cold fuel brings the pressure down noticably. Once the engine (and fuel) warms up the pressure moves up a little. I'm sure this is normal to all pumps but when you're only starting out with 5 psi you tend to stare at the guage on cold mornings.

On the plus side. . the engine starts, idles and runs just fine (wow... isn't that what a Cummins engine is supposed to do??).

If I keep the truck I'm leaving everything as is until it runs out of warranty and then the old LP will go back on to run in series with the tank pump. If I sell this rig I'll never own anything with a VP44 injector pump..... period. HPCR is the way to go anyway.

For now our winter trips to Mexico will stay very close to the border. I'm really worried about getting too far from a repair facility that carries VP44's and can swap them out. A pusher pump ,FASS or something would certainly help matters... . but I have no faith in the VP44. Some fail mechanically, some electrically. Some fail with good fuel pressure. . all fail with poor pressure. The thing is just fragile. If you noticed... Cummins didn't stay with it too long.

I think the 2nd generation 24v Cummins is a beast of an engine. It has one problem and one problem only... and everyone here knows it... the VP will fail without notice.

Mike

 

[Bob4x4]

Bob... do you know that for a fact? What do we know about that in-tank pump? Who makes it... . what kind of pump is it... has it been used in gasser applications or is this something designed for diesel fuel only... . if it stops (fails) does it become a restriction or will the VP suck fuel through it???

This info may have been posted already (I've been on the road for awhile) but I don't know squat about this pump.

I did gripe to the dealer that installed mine. They weren't happy with the fuel pressures either but apparently DC is. Here's a little update on my pump with about 5K miles on it.

It's seems very sensitive to fuel system conditions. I just changed out the fuel filter and picked up about 1 to 1 1/2 psi. Cold fuel brings the pressure down noticably. Once the engine (and fuel) warms up the pressure moves up a little. I'm sure this is normal to all pumps but when you're only starting out with 5 psi you tend to stare at the guage on cold mornings.

On the plus side. . the engine starts, idles and runs just fine (wow... isn't that what a Cummins engine is supposed to do??).

If I keep the truck I'm leaving everything as is until it runs out of warranty and then the old LP will go back on to run in series with the tank pump. If I sell this rig I'll never own anything with a VP44 injector pump..... period. HPCR is the way to go anyway.

For now our winter trips to Mexico will stay very close to the border. I'm really worried about getting too far from a repair facility that carries VP44's and can swap them out. A pusher pump ,FASS or something would certainly help matters... . but I have no faith in the VP44. Some fail mechanically, some electrically. Some fail with good fuel pressure. . all fail with poor pressure. The thing is just fragile. If you noticed... Cummins didn't stay with it too long.

I think the 2nd generation 24v Cummins is a beast of an engine. It has one problem and one problem only... and everyone here knows it... the VP will fail without notice.

Mike

Yes, I have seen this. If you notice my sig I skipped the vp44. I have replaced way too many to want to own one. I make a fair living off that era truck. The 3rd gens may make me go hungry :-laf . The 05 has the in tankpump and makes me nervous,I have driven my truck off road to places it could not be towed out of. I am thinking of building a complete parallel fuel supply system for my own. I am not interested in dropping my tank in the boonies to replace a failed fuel pump



Bob

 

[NoSeeUm]

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.

This is not quite true in all cases.



I am un-sure exactly of the Carter LP design. Is it a vane type positive displacement pump?



Positive displacement pumps deliver a constant volume (flow rate) and are generally high pressure protected by a pressure regulator that recircs fluid back to the suction source. The recirc is capable of recircing the full volume output of the pump with the pump discharge pressure at maximin under these conditions. The discharge pressure is set by the pressure regulator, without it the pump would continue to build pressure until something ruptures, breaks or the motor is electrically disconnected.



If piped in series with another pump, as the flow demand of the second pump increases the discharge pressure of the first pump will drop. The pressure regulator will recirc less as fluid is being pulled by the second pump. If the second pump attempts to flow more liquid than the capacity of the first pump the discharge pressure will drop to zero (or below zero).



However, the flow volume provided by the first pump will always be constant under all conditions and only the discharge pressure will fluctuate.



So in thinking about this, if too much pressure kills the VP then it would make sense to lower this pressure. Simply install a pump that delivers a constant volume (flow rate that is adequate) at a lower pressure. IMO this would work great until the discharge pressure of the LP went to zero. Making me think that the VP would be attempting to pull more fuel that the LP could deliver. This operation at zero (or below zero) pressure is the part that makes me question the in tank system.



Jim

 

[steved]

I believe using the intank pump (which is most likely a centrifugal) and the fuel bowl mounted pump (has to be a gear pump) would not be that detrimental. But, you still have the same issues if the fuel bowl mounted pump fails (dead in the water)... the intank pump would still allow fuel to bypass if the pump failed... so a secondary (external) pump would get you home. Also, I think you will find that the pumps are built to bypass internally since they have no returns on them... they basically pump the same fuel around in the pump head until a demand.



I still think we are worried about, and focused on, the pumps themselves when we should be looking at the factory plumbing restrictions first, then sizing a pump up to overcome the restrictions (or removing the restrictions).



The more I read, the more I feel that the LPs are failing for two main reasons: They are mounted to far above the tank and they are fighting to push fuel through a very restrictive fuel delivery system... both these will stress a pump.



steved

 

[Bob4x4]

you guys keep talking theory,I have seen most of these scenarios on a regular basis. Electric pumps will fail,period. If a stock pump on an 03 fails the pusher may not be able to push enough fuel through it to run. The same with a 2nd gen if the pusher fails the stock pump will not get you down the road with any certainty. If the in tank pump fails the pusher will not be able to pull enough fuel through it to run properly,in some cases it will be a tow-in. The only question is when, not if. Even the Rasp has issues... ... ... . do not put too much tension on the belt. The Fass has its own issues as well. There is no perfect set-up. Some work longer or better than others. I love fixing the trucks that belong to the engineers,they have all the theories but gee they still come in on the hook :-laf :-laf :-laf



Bob

 

[Don Bellamy]

The web site of Blue Chip Diesel Performance Inc has posted "BOSCH VP44 INJECTION PUMP AND LIFT PUMP FAILURES EXPLAINED" and after reading that along with this post I don't think anyone is on the same page concerning this subject!

Don

 

[BobMay]

Not to change the subject but... ... I am trying to locate a OEM lift pump for my 2000 2500, my local dealer has 3 in stock but wants $389. 00. I thought the list price was in the $150. range. Can anyone confirm what the current price is?



Thanks Bob

 

[steved]

They are $161 from Cummins... dodge marks them up for the profit. If you buy one from Cummins, be aware that you will need to also buy a $8 wiring harness to connect the Cummins pump to the Dodge wiring (this is a one time purchase).



steved

 

[CFAR]

They are $161 from Cummins... dodge marks them up for the profit. If you buy one from Cummins, be aware that you will need to also buy a $8 wiring harness to connect the Cummins pump to the Dodge wiring (this is a one time purchase).



steved

Depends on the year, mine an 01. 5 did not need the pig tail, Even though it was "INCLUDED" with the pump. I believe it was the 98. 5 and 99's that needed the pig tail. I'm to lazy to go check to see what year BobMay's truck is.