Hi folks. I am interested in settling on the right fuel transfer pump for my 1998.5 24V 2500. My engine is stock. I have no plans to increase horsepower or torque. I have 157,200 miles. 
I bought the truck last August. Right before I bought it,  the VP44 had failed and been replaced in June. However the lift pump was not replaced.  I decided to dig in a learn a bit about this known problem. I purchased a fuel pressure test gauge and checked the stock Carter pump. Readings were ok for the stock system, but a little down. I decided to change it out ASAP with another stock Carter pump at that time. I wanted to experiment and track some results. With the new Carter in I was getting 10 psi at idle. Dropping down about 6.5 to 7 psi pulling a steel hill. I proceeded to install a digital ISSPRO fuel pressure gauge and drove in that state it over the past winter.  

 

Over winter, I continued on to read about various high performance fuel lift pumps. I bumped into the Airtex or Herko fuel lift pump. Priced at about $70 so I decided to try the Herko. I put it in about a week ago. Fuel pressure at idle is 16-17 psi. Pulling hills drops to about 9-10 psi. A considerable improvement over the stock Carter. Hi-way speeds on flat ground the Herko makes about 14 psi. My understanding is the check valve inside the VP44 opens at 14 psi allow for proper full cooling of the pump electronic circuit board. Is this correct? It seems odd to me that the Bosch needs to see 14 psi to cool, yet Dodge engineers chose a max-10 psi at idle, fuel pump. 

 

I own a 23 ft travel trailer I plan to tow. If the VP44 does indeed need 14 psi for proper cooling, I suppose I should be looking at a pump that can maintain minimum 14 psi at all times. Am I on the right track here? Do I really need to be looking at these expensive AirDog or FASS pumps at $600 to $800? Seems pretty pricey for a stock HP truck. I understand that saving the VP44 is the idea here, as they are big bucks. Looking at the Gino's catalog here as I type this, they offer a mid-level upgrade. The FASS High Performance Adjustable Fuel Pump at $464. I assume if I go this route I'll also need to upgrade the fuel suction lines.

 

It's been interesting learning about the various pump options. I have already spent $200 screwing around with pumps and learning. I do my own work and do enjoy it. Thoughts and tips settling on the right right lift pump for me are appreciated. Thanks. Keith

 

Edited March 24, 20196 yr by keithb7

Because the return port in the VP44 is too small for higher pressure and could possibly push the front seal out. Rare but has happened. Return is on the left.

 

21 hours ago, Tractorman said:

Actually, it is not odd.  There is a fixed displacement vane pump inside the VP44 injection pump.  This vane pump rotates at the same rpm as the VP44 and provides fuel flow for cooling of the VP44 as well as some other duties.  The internal vane pump provides much more fuel than is being consumed by the injectors.  Consequently, the fuel pressure rises internally and the excess fuel is forced over a relief valve that is set at over 100 psi (not sure of the exact pressure) and the fuel is returned to the suction side of the internal vane pump.  The inlet of the 14 psi relief valve is in common with the outlet of the internal vane pump (operating at more than 100 psi), so there is always fuel flowing over the 14 psi relief valve regardless of the lift pump pressure.

If I am reading this right you are saying the internal vane pump is where the pressure comes from to open relief valve and not the lift pump.

 Many years ago after receiving the in tank pump from Dodge I started having some bucking and dead pedal issues. Took to a diesel shop in Maryland that some time trying to find the issue. The only thing they found was low fuel pressure, 5 psi at idle and near 0 at WOT. I added a booster pump on the frame and it cured the issues I was having. I have no idea what pressure I had since I had no FP gauge nor knew of the need for one. I was pretty ignorant as to what made this truck back then,

1 hour ago, dripley said:

If I am reading this right you are saying the internal vane pump is where the pressure comes from to open relief valve and not the lift pump.

 

Yes, that is correct.  The internal vane pump generates more flow than can be used by the combination of supplying fuel for the injectors, internal control circuitry, and fuel flowing over the 14 psi relief valve returning to the tank regardless of any fueling demands.  Because more flow is being generated than can be used, the pressure must rise to the relief pressure of the internal vane pump (over 100 psi) and flow the remaining fuel to the suction side of the internal vane pump.

 

The lift pump must always generate more flow than the combination of the fuel being consumed by the injectors and the fuel being returned to the fuel tank from the VP44.  If the lift pump does its job, there will always be a positive fuel pressure reading at the test port.  The remainder of the fuel flow from the lift pump will flow over an internal lift pump relief valve and either return to the suction side of the pump or return to the fuel tank via a separate line.

 

2 hours ago, dripley said:

Many years ago after receiving the in tank pump from Dodge I started having some bucking and dead pedal issues. Took to a diesel shop in Maryland that some time trying to find the issue. The only thing they found was low fuel pressure, 5 psi at idle and near 0 at WOT. I added a booster pump on the frame and it cured the issues I was having. I have no idea what pressure I had since I had no FP gauge nor knew of the need for one. I was pretty ignorant as to what made this truck back then,

 

I don't have an explanation for this situation as there are some unknowns here and as you said this happened many years ago.  It is possible that under wide open throttle, there were disruptions of fuel flow that the test gauge didn't show.  Any disruption of fuel flow could cause bucking.  When you added the booster pump, that could have masked the true flow problem and made the symptoms disappear.  Just speculation on my part.

 

It is very interesting that you mention this, because I am experiencing a similar condition, but only when towing up a continuous grade with a steady throttle, and not at full power.  This symptom has appeared after installing new RV275 injectors.  Our definition of bucking could be different, but I am going to try to figure out what is going on and I may even get to the point of adding another lift pump in series just to see if the symptoms disappear.  If I do this, I will post the results.

 

- John

5 hours ago, Tractorman said:

It is very interesting that you mention this, because I am experiencing a similar condition, but only when towing up a continuous grade with a steady throttle, and not at full power.  This symptom has appeared after installing new RV275 injectors.  Our definition of bucking could be different, but I am going to try to figure out what is going on and I may even get to the point of adding another lift pump in series just to see if the symptoms disappear.  If I do this, I will post the results.

The bucking I experienced was very much like the engine shutting down for split second. A pretty jolt. Mostly when I was towing like you mention or a WOT run at higher rpm empty. It happen to me before the oe VP crapped out at 75k. A filter chznge cured that though. Who da thunk you have change those things. A filter change did not however cure the problem after the intank pump was installed but the booster pump did. I ran that set 3 or so years before installing the AD. I came across it today while digging out the rear lifting ring for the head.

That is a BD Diesel booster pump from 11 years ago.

Edited March 27, 20196 yr by dripley

Boy, I remember those days long ago... Been there done that... 

 

full meal deal FASS

I did the raptor 150 and plumbed from the tank to injection pump. Snake river diesel put together a kit because I had to remove the factory retrofit pump from the tank. 

My Raptors on the frame rail. 

I idle at 20 and drop to about 15 pulling a steeper hill towing. Empty the needle doesnt drop very much below 20.

 

It's been on about 8 years I think. I've raised pressure 3 or 4 times to maintain 20 at idle.

Very damn nice truck