Fuel Pressure Limit for the VP44

[mopars1]

I know there has been many a discussion on this subject but, I have some new specs out for the lowest pressure at the injection pump at wide open throttle. This information is new from the STAR Hotline. They made the statement that under no circumstances should the pressure fall below 8 PSI. They said if the pressure drops below this in any form it could or will eventually take the injection pump out. We had a truck in the shop that would set an injection pump timing failure code and at times it would not accelerate faster than 0-30 in about 30 seconds. After running some tests it was becoming obvious that the injection pump was failing. You cannot get one under warranty without ordering it through the Star Hotline. After talking to the Hotline, they said to replace the transfer pump. We were amazed at this request but they would not send an injection pump. After installing the new transfer pump the pressure at idle was 16 PSI and out on the road at WOT the pressure did not fall below 10 PSI. This is on a stock engine with stock lines. I know there is a long thread about pump pressures, etc. and I am not an engineer that might know a lot about fuel flow and pressures. This is just some new information that is not in the owner's manual or the service manual.

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2001. 5 2500 Sport ETH/DEE, 3. 55 Dana 80, std cab, 4x2, Intense Blue, Agate, all options except leather and keyless entry. Dawson 24ft hauling a 1970 Dodge Dart Swinger drag car; 360cid auto; runs 10:00 in 1/4 mile. I wish my truck ran this quick!

 

[Mick2500]

Mopars1,
Thanks for the tip!!! Did you happen to test YOUR truck? Sounds like you have access to lots of good info. #ad

Have you also heard that the tire size calculations have been expanded to include revolutions per mile as low as 599? Read it somewhere else tonight but there is some conflicting info from another member.

Thanks,
Mick

PS You have good taste in colors too. #ad

<font color=blue>

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2001. 5 2500 ETH/DEE, QuadCab, 4X4, SB, LSD, 3. 54, SLT+, Sport, Intense Blue PC/Agate, Tow Package, Camper Package, 'DC' Bed Cover, Sliding rear window. Totally STOCK!!
On Order 4/28/00
Arrived 9/14/00 !! #ad

My Truck

[This message has been edited by Mick2500 (edited 05-14-2001). ]

 

[mopars1]

Mick, at this time I have not even put a pressure gauge on my truck, but I am about ready to! No, I have not heard of any of the upgrades for changing tire size and reprogramming the controler for the correct MPH. I will have to look into this. The new zone Tech Advisor is visiting my dealership tommorrow. If I can I will pump him for as much information as I can get!

EDIT: I just tested my pressures at idle. Did not have time to go out for a WOT run.
14PSI before the filter. 14PSI at the pump.

David

[This message has been edited by mopars1 (edited 05-14-2001). ]

 

[TXRam]

Thanks for the info, but I have to throw in my $0. 02 worth. I believe the "8psi" limit you were given is because anything less than that is indicative of a bad lift pump on a TOTALLY STOCK truck.

Per Bosch, the VP44 is designed to suck fuel from the tank and through a filter. Therefore, I cannot believe that a pressure below 8psi is going to hurt my injector pump. I know I'm sounding like a broken record, but as long as you have any positive pressure(1+psi) at the inlet to the VP44, it is AOK IMHO.

 

[B. Gill]

TXRAM i agree with you ,i think VP44 may not even need a feed pump and why Cummins has it is due to the reason as it is mounted so high one the engine plus the length of the fuel line from the tank might have made it imperative that a transfer pump is needed.
i think what happens is that when the transfer pump goes out completey or it goes out slowly, in the process the internal restrictions when it is not working well starv the VP44 and thats when it starts to damage itself as there is not enough fuel to lubricate and cool it. if we can find at what pressure the internal pump in the VP44 supplies fuel to the plunger then any transfer pump with reasonable volume and fuel pressure, within a few PSI below that would work fine IMHO.
bob

 

[TXRam]

What was your WOT pressure at the injector pump with the old lift pump? If it was zero, most likely it was just another restriction in the line - then, yes, it could cause poor performance.

 

[pwr2tow]

I understand what your saying but to say the vp44 does not require any additional help for performance purposes (Stock performance) in my opinion is wrong. The vp44 will probably (???) suck fuel but to get the full benefit of performance and longevity IMO it needs help. May be this is a bad example but a carburated engine will run on gravity flow but to maximize its performance you need a pump with a regulated pressure of 7 psi. I know this is not a gas engine but I can not think of a better example right now.
Ron

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1999, 3500, 6x6, slt, auto, 3. 55, Qd cab, ISB cummins, Isspro transmission temp, EGT, Boost gauges on A-piler, fuel prssure gauge, DD stage 1, DD TTPM, modified banjo bolts, K&N 0880 with prefilter, triple trailing 2001 26RKSS Tahoe 5th wheel, 1999 120hp 1800 bayliner. 20,000 lbs GCW.

 

[Mick2500]

Thanks for the data David! As soon as I get
some time, I'm going to rig a presure gauge on my 01. 5 just to see what it's reading. No performance problems at all but I don't want to cause one either.

Mick
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2001. 5 2500 ETH/DEE, QuadCab, 4X4, SB, LSD, 3. 54, SLT+, Sport, Intense Blue PC/Agate, Tow Package, Camper Package, 'DC' Bed Cover, Sliding rear window. Totally STOCK!!
On Order 4/28/00
Arrived 9/14/00 !! #ad

My Truck

[This message has been edited by Mick2500 (edited 05-15-2001). ]

 

[jmeehan]

I remember a post from awhile back where another member took his lift pump apart and found plastic debris inside. Maybe some of the pumps are getting plugged by debris and the lift pump cann't draw enough fuel through it.

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ex Ford tech, now driving '01. 5 2500 4X4 QC LB ETH/DEE SLT 3. 54, Patriot Blue

 

[MCummings]

I think a thought that is getting forgotten here is,,

The VP44 is Lubricated AND Cooled by diesel fuel.

My VP44 Failed because of a lack of pressure, and too much heat. Previously I had about 2-3 Lbs of pressure Before I had the Lift pump replaced,, then about 800 Miles later the VP44 failed because of being previously overheated.

Just my two pennies.

MerrickNJr

[This message has been edited by BOMBER_101 (edited 05-15-2001). ]

 

[pwr2tow]

If the vp44 does not need fuel pressure then please explain the performance increase I and a few other TDR members experienced when we changed our lift pumps. I even get smoke now at start up and excelleration which I never got before the lift pump change-out. Smoke on excelleration tells me I am getting more fuel now then before. FYI it does not matter if I have my fueling box pluged in or not.
Ron

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1999, 3500, 6x6, slt, auto, 3. 55, Qd cab, ISB cummins, Isspro transmission temp, EGT, Boost gauges on A-piler, fuel prssure gauge, DD stage 1, DD TTPM, modified banjo bolts, K&N 0880 with prefilter, triple trailing 2001 26RKSS Tahoe 5th wheel, 1999 120hp 1800 bayliner. 20,000 lbs GCW.

 

[TXRam]

OK guys, if what you're saying is correct, then my truck WITH TOTALLY STOCK FUEL SYSTEM, Hot PE, EZ Edge, and 275 injectors won't run any better than stock and my VP44 should have self-destructed about 25K miles ago. #ad


Yes, I've checked the pressures - I guarantee it's less than zero at the inlet to the pump. Yes, I'm working on my own design for the fuel lines & pump location - zero is not good, but 1-2psi is not too low on a BOMB'ed truck. 1-2psi on a stock truck says you have a filter or lift pump problem. Guess what? When a lift pump is going bad internally, it WILL heat up the fuel more - this itself can cause poor performance and destroy the VP44.


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1999 2500 QC 4X4 LB Auto (DTT Upgraded), 4. 10LS, 275HP Injectors, PowerEdge, PowerEdge EZ, SPA Boost and EGT, K&N Air Filter, Magnaflow straight-thru muffler
NRA Member

[This message has been edited by TXRam (edited 05-16-2001). ]

 

[pwr2tow]

TX, contrary to what you just said is if you do not have a lift pump in line then yes you would not see much performance over stock. In other words take the lift pump out of the system and see how long the vp44 lasts or how much performance there is. Remember even though you have all your power mods on your truck you are not useing them all the time, just on fun occasions. It is the fun occasions that you are seeing zero psi and that is the reason your looking for different fuel lines and pump location.

 

[DBlaze]

With all the talk about bad lift pumps, has anyone figured out what exactly goes bad on them? I changed out my lift pump just a couple of weeks ago and do agree that there is a seat of the pants change in performance. At the same time I took my old pump apart and the rotor and vanes are like new. My only guess is that the motor is the culprit. Anyone found their pump worn out?

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'99 3500 QC, 4x4,5 speed, Intense Blue, 275's drilled air box, silencer ring MIA, Geno's M-E pipe.

 

[MHindman]

I had an interesting problem with my truck, and it points to what some of you are saying. I had the Lift pump and the injection pump go out at the same time. My service manager said that hes seen this before. I am assuming that the lift pump went, then the injection pump sucked from the tank for a while, but then died. They fixed it all, but it was good to know im not the only one. And i think one of the main reasons we have two pumps is to bring the fuel to the injection pump on start up, and like someone said... its a long way to the tank.

 

[MHindman]

I had an interesting problem with my truck, and it points to what some of you are saying. I had the Lift pump and the injection pump go out at the same time. My service manager said that hes seen this before. I am assuming that the lift pump went, then the injection pump sucked from the tank for a while, but then died. They fixed it all, but it was good to know im not the only one. And i think one of the main reasons we have two pumps is to bring the fuel to the injection pump on start up, and like someone said... its a long way to the tank.

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(Silver Bullet)1999 Ext Cab 4X4 5SPD, All options. Power Max 3(adjustable), K&N Filter, no muffler, Pyro,Fender Flares, Toolbox, bedrail covers, 450 watt Kenwood Sub, 33 12. 50 16. 5's, 3. 54's... Soon to have: 4inch, DDIII's, Southbend clutch.

 

[mopars1]

Well, in my second post of this thread I stated the Zone Tech Advisor was going to visit the dealership. That is what we where told. It ended up being Warranty personnel from the zone looking at our warranty repair orders to see if we could cut some corners. There will be no tech advisors for my zone. We have to rely on the Star Hotline for all our needs. We were lied to by the people who called the dealership and said they were tech advisors. Another bald faced lie by Daimler.

 

[thepitts]

I get my third lift pump this friday, 1 psi at wot. Hope this one last a lot longer.

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Eric Pitts 2001 Properly Valved 2500 Qcab 4X4 auto Transgo shifts it 4. 10 LSD Weston Nerf Bars Smith built brush guard Command Remote Starter Scotty Air DD stage 1’s, PS boost module , elbow 32psi boost 247hp,657tq Neophyte B. O. M. B. er Hella drive/fog lights,Aircraft landing lights
The Pitts Home Page
Member GLTDR

 

[Mick2500]

mopars1,
Join the club... . I think we have ALL been lied to a time or two by DC. Through my entire 5 month waiting period only my salesman told me the truth. #ad


Samscov,
I'll post my gauge attachment adapters as soon as I get time to play with it.

Mick

 

[Mopar-muscle]

the schrader valve is a -4AN , if you get a hose end adaptor to 1/8 npt you can use a tire valve stem core remover to remove the schrader core , them put on your adaptor and go to a gauge , a cheap alternative is to get the DC gauge , its cheap and you can get your snap on dealer to get it for you , if you have access to the snap truck , if not go to www.spxmiller.com and order it . i'll get the number off my gauge , spx search ins't working for me ... but number i keep seeing is C-4799

[This message has been edited by Mopar-muscle (edited 05-17-2001). ]