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Engine/Transmission (1998.5 - 2002) New VP44 Theory???

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jerryrigg

The overflow valve on the VP44 is designed to open at 14psi, thus dumping fuel back to the tank. If the valve is stuck in the closed position, you can receive a DTC indicating a "High Injection Pump Fuel Temp". This is due to no "circulation" of fresh fuel. We all know the fuel is the lubricant and the coolant for the pump. The acceptable minimum pressure (per the manual) of the lift pump is 10 psi (pre-filter) this is not enought to trip the overflow valve so circulation is achieved through a constant flow of fuel to the injectors. At idle you do not have a constant flow, the ECM provides just enough to prevent shutdown. Thus explains why it is not good to idle the 24v for extended periods.



Those of you that have added a pusher pump and are getting pressures over 14psi have a constant lubricating and cooling system for the VP44 as well as helping the lift pump.



It would then seem to me that the ideal solution is a single pump back by the tank, that give you a minimum 15psi at the VP44 (post filter or filters) but provides a flow rate high enough to prevent low power due to bypass of too much fuel.



So my questions is, does anyone know what the required flow rate (gph) of the VP44 is at WOT. If we can find a single pump that slightly exceeds the require flow rate and exceeds 14psi at WOT all our problems would be solved. (I'm knocking hard on wood here)



-Matt
 
Do a search there is a massive thread with flow numbers listed.



Alot of people are trying single pumps back by the tank, however the current problem is finding one to last! One of the more successful adventrues is csutton's truck, he has an aeromotive pump attached to the bottom of his tank, I believe its been going for over a year now.



There is information in older posts, do some searches and grab a beverage and enjoy the reading.
 
This was exactly my thought when I using my last Mallory 4150, unfortunately, it came to me too late as the pump was already starting to lose psi's. I was going to up the psi's from the Mallory pump to a minimum of 15 at idle, thinking that the return would always be open and the pump wouldn't be beating itself to death while at idle.



The pump I'm using now is set for 16 psi's post FF at idle, with the same thought. So far it's been working great, time will tell. The pump I'm using is rated for 270 GPH, beyond overkill and not why I chose it. I can tell you that, with an at idle psi of 16 + psi's, I never go below 10 psi's at WOT and that's only with the TST set on KILL. Normal driving see's 14 psi's while cruising on flat ground at 55 MPH.



Scott W.
 
Jerryrigg-----The lift (feed pump) does not open the VP44 return press. regulating check valve. The VP 44 has an internal vane type positive displacement pressure pump that builds high pressure to charge the pump plungers,actuate the advance mechanism and pressurize the pump housing. The check valve dumps excess housing pressure and regulates it at 14 PSIG,which also helps to cool the pump.
 
Royal...



That was my orginal understanding but I am beginning to question this...

One reason I have yet to find this stated in "writing", the manual does not specifically state this, and most of the manuals discussion about the overflow valve is in ref to the lift pump. The Overflow valve testing/removal/install procedures is after the section on the lift pump not with the injection pump.

My second reason is the VP44 is designed to take low pressure fuel from the lift pump and crank it up to injection pressures. The injector does not spray fuel until the spring tension of 4,500psi is reached. Well that is 4,486psi above the overflow valve setting. Which tells me if the VP44 was controlling the valve instead of the lift pump it would never close.

I'm trying to figure out a new test, I'm thinking that even with the engine off if I pump say 16psi into the banjo from the filter and loosen the overflow banjo and fuel comes out then I'm headed in the right direction.

I may be way out in left field on this, but this is the way I am putting all the data together. Now if you can point me in the right direction to the "gospel" of the VP44 I'd appreciate it.



-Matt
 
Royal, it's my understanding that the first stage pump in the VP-44 produces 300psi and that the overflow valve does indeed 'regulate' the inlet pressure from the lift pump.



Do you have information or experience that supports your concept?



Thanks



Tom
 
Jerryrigg----As I said in my original quote,the vane type pump charges the pumping plungers for the high pressure fuel to the injectors. There are 3 pistons(plungers) in the distributer rotor of your pump. These plungers are actuated by a set of shoes & rollers that run inside of a cam ring. These plungers(pistons) generate enormus pressures to the injectors . The housing pressure is a result of leakage inside the pump,and some application use a bleed orfice which is used to eliminate any air bubbles in the fuel and send them thru the return ck. valve to the tank. Go to a Bosch service dealer near you and they can show you a diaghram of the VP44.
 
Fuel Requirement At WOT

JerryRigg,



I beleive to calculate the fuel consumption at WOT one would have to facter in the horsepower of the vehicle. Fuel = power. My truck might use more fuel at WOT then yours.



But, what about this... We drive for exactly one hour at 100 mph in our 300 horsepower truck and at that rate we get 10 miles per gallon. We use 10 gallons to run the engine. We know that 70% of our total fuel is used for cooling. Using "Diesel Math" we quickly find that we used approximately 23 gallons of fuel for cooling the pump, or a total of 33 gallons.



Does that help you with your theory?
 
VE Pump

The VE pump the book appears to focus on was used on the first gen trucks. It had no electronics on it as I recall. Very different from a VP44 which is quite dependant on electronics.



I'm sure the book is awesome regarding the VE pump.
 
paging Dr. Freak....Dr. Diesel Freak.........

Where is that cd that you can order for like $20? Doesn't Diesel Freak have it?



Andrew
 
Solenoids

Thanks for getting back to me on that question NXS. As you could tell I was baiting folks into a conversation. To answer my own question I would say there are two solenoids. One for fuel to the injectors, and one to control fuel for cooling. There are four wires going into the center of the pump. We tap one of the wires when we install the clip on fuel boxes. That leaves three wires. I beleive there is a second solenoid that directs fuel to the cooling passages.
 
TexDieselYoung'n'

I think TxRam must have a mighty fine wife cause he doesn't seem the least bit interested in hanging around with us and getting grease on his duds. More power to him I say!
 
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Turbo Diesel Register
Issue 128 – Digital Version
Digital Magazines
FREE!
TDR Test Drive - Digital Edition
Renew
Subscribe
Gift Subscriptions
Back Issues
Subscription Status
Address Change Form
Buyer's Guides
Ram Diagnostic Trouble Codes
The Perfect Collection
The Perfect Collection Vol. II
TSB Updates
Dodge/Cummins Historical Overview
Cameron Collection
What Makes Us Tick?
Product Showcase
Advertising



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