Well I hope this doesn't become a but I'll go there anyway. Got a 2001 and lost the IP about 20,000 km ago. Changed the Lp at the same time for the chrysler in tank lift pump, thinking that would be great. Pumps push way better then they pull and in tank they have fuel to cool them. Gassers have had them there for about 20 years. Then I started to upgrade the performance of the truck. In doing so I have come across a lot of negative feedback aimed at this pump( which is also in all the 2003 and up trucks) From what I've heard, this pump will pump 40 gph, Which is my entire full tank every 40 minutes. This is way more than I can burn with my mods in that time period pulling a trailer, the pump itself is capable of about 89 gph without the elaborate module by chrysler, so if the volume is being delivered to the IP, Why is the pressure such a focal point?? The VP44 shouldn't cavitate with this fuel rate should it? So is mechanical damage brought on by lousy lubrication from low sulfur diesel? With lower pressure (under 5 psi) does the fuel not cool the pump adequately?

Anybody have thoughts on this. It sucks having to know "why" things work the way they do.

 

Put a holley blue on it with the in-tank and forget about it, you will have noless than 15 psi at WOT.

 

Carp, I like the way you think.

There are many myths about what fuel pressure is needed to keep the VP44 alive. Here are my thought based on research I have done.

Myth 1) High lift pump fuel pressure is needed to cool and lube the VP44.
It is true that the IP is cooled and lubed by fuel and the heat generated in the pump flows back to the fuel tank. Tests of the flow have shown if the engine is running at one RPM and the lift pump pressure is varied from 0 to 25 PSI the amount of fuel flowing back to the tank does not change. Higher lift pump pressure does not increase the cooling or lube.

Myth 2) DTC P0216 (IP Timing Failure) is caused by low lift pump pressure.
A failed lift pump or a clogged fuel filter can cause this code if they create a negative pressure at the input of the VP44, but with any positive pressure the code is caused by wear of the timing piston. Early VP44s (‘98 + ‘99) used the aluminum pump case to house the piston and they failed causing the piston to stick and throw the code. The fix by Bosch was to press in a brass sleeve to help but these also failed. Finally they used a steel sleeve and the problem was much reduced but not entirely eliminated.

Myth 3) A lift pump pressure of 8 PSI or greater is needed to prevent the diaphragm between the lift pump and higher pressure VP interior from cracking.
This diaphragm was a problem in early pumps but has been thickened in all of the rebuilt pumps. Vibrations caused the cracking from the high pressure radial pump dumping after an injection event.

Myth 4) The spillback valve on the VP44 is used to control the lift pump pressure.
Flat out wrong. At the input of the VP44 is a 4 vane, positive displacement pump that passes a fixed quantity of fuel per revolution of the pump. This pump creates a pressure in excess of 200 PSI and is responsible for the fuel flowing back to the tank. The lift pump pressure can have little effect as long as it is a positive pressure.

There were also problems caused by the electronics giving out due to temperature cycling from a cold start to high temps from under hood. The electronic circuit boards and components are subjected to temperature cycling. With a mismatch in thermal expansion rates, the solder joints can fatigue and become intermittent. Newer rebuilds have redesigned the circuit boards to correct the problem.

I believe Bosch rushed this VP44 into the Dodge to help meet EPA pollution standards when the P7100 used in the 12 valve could not be made clean enough. Obviously, not enough testing was done to find and fix problems before we got the ISB in our trucks.

I have my flame proof suit on

 

I'm with ya all the way... I respect a man that calls a spade a shovel... I have worked with computers since DOS version one (circa 1981) and windows version 2 (circa 1985). Feed me lettuce and call me a guinea pig...

 

The in-tank will run a stock truck just fine. You have a comp and 90hp sticks in your sig. It will need alittle help with that.

 

The only question is do you always have a positive fuel pressure at the input of the VP44? If no, a new lift pump is needed.

 

Dave, that is some of the most interesting stuff I have heard yet.I appreciate the response. I think I'll install a fuel pressure guage to monitor that the pump is running as opposed to how much it is pumping. I have been running the better injectors for some time now with no ill effects to my New Vp44. The comp and super B are only about a month old and all I've noticed so far is better fuel mileage and a funny little smile on my wifes face when I pull 44 pounds of boost. I have a BD lift pump, but have not installed it yet. I could not see the sense in installing a higher volume pump in line with a lesser volume pump. I know it works and don't meen to bad mouth anybodies thinking, just my own logic has me trying to find another way. I may fabricate a higher volume gerotor pump to my sending unit and install that in tank. Until I change something, I guess that I'm betting $1700 that my in tank is enough.

 

i agree 100% , you hit the [U]nails[U] right on the head.... if my electronics hadn't failed i think i would have gone another 180,000 miles

 

For anyone interested on a couple of good sources of info about the VP44, I can recommend a book published by Bosch, Diesel-Engine Management (ISBN 0-8376-1353-1). This book has several chapters showing the operation of the VP series of injection pumps along with the older mechanical pumps and new common rail pumps.

There is also a CD put out by Bosch, Radial Plunger Distributor Pump VP44. This CD has animation of the operation of the injection pump showing how the various components work. It is a good overview but lacks information on the specifics like fuel pressure.

An Internet search will turn up places to find these.

 

No such thing as too much good info. Ordered them today. Thanks again.

 

Hello guys.. I just went through a situation with my lift pump, it didnt work all the time.. Replaced it with a holly blue pump on the frame rail and learned a few things, along with the holley ran 2x then quit. The stock ECM had no positive output, I assumed I damaged the driver then found the holley only drew 3 amps. When you remove the stock pump and plumbing the 2 banjo fittings and hose that go from the lift pump to the filter head you will notice how restrictive these 2 fittings are compared to the one that the line from the tank feeds. I moved this larger fitting with the pressure tap to the filter head inlet. I cut the steel line from the tank and clamped some aeroquip blue hose to the pump and then up to the filter head. I then added a 15 psi switch on 3 feet of braided line to the oil filter housing (plug on top) 1/8 pipe. I supplied the positive from the distribution block with a fuse and used the switch to supply the ground, truck never ran this good! I did learn in the interum that the truck will not start with the pump running when I had it run straight to the battery till I could get it right. I had to start the truck then connect the pump power to operate.

 

I replaced my lift pump less than a year ago(about 15k mi) with a new in tank one from chrysler(along with my IP). Anyway at the same time I installed a FP guage. The LP brand new only pushed 11 psi at idle. With just my custom program in the ECM (about 50hp), under WOT it would drop to about 1/2psi. I now have a Holley black pump along with my in tank and pressure never goes under 16psi under WOT. With your bigger sticks & Edge Comp, I guarantee under WOT your VP is seeing almost 0psi.
Later,
Tommy

 

i just replaced my lift pump today, what i noticed about psi is if your pump cant overpower the banjo check valve, then you have no fuel cirrculation. a pump can have all the volume in the world, but, if it can't develop 14-16psi (as per dodge fsm) the valve stays closed. what i don't understand is why dodge says that 10 psi is the min. that isn't enough psi. my pump i put on is a holley hp 150. pump psi is 17. and for the first time ever, i noticed a big diffrence in ip temps ( along with engine running a little smoother, and noticeable power return) . along with that a fuel return line that was warm, and also my fuel tank. i don't know just how hot the ip can handle, but, when you start with a ip that you can't touch to one that is just warm(100-120? best guess). then that must mean something

 

bent valves, that post is interesting, but I'm puzzled. if there is 200psi and that is what opens the check valve, then why bother with one at all? 14-16psi is nothing to that kind of psi.
I'm not criticizing or arguing with ya, I'm just trying to better understand this fuel sys.( perticualy on how/why 2 pumps with equil volumes but diffrent psi can effect ip temps. oh, ya don't need the flame suit)

 

Is more expensive, but I FASSed mine. DPP was very helpfull.