Engine/Transmission (1998.5 - 2002) My answer to the oem lift pump problems

[Whitmore]

We all know that the oem lift pump is not very good to say the least, I am on my second pump now and after thinking about the system as a whole I have come to the conclusion that the pump is not the problem, its how it is set up, no pump likes to pull a vaccumn they all want a positive pressure, this theory has been proven to a point by some folks adding a pusher pump, when this is done the oem lift has alot better reliability, the reason is that the pusher is now supplying a positive pressure to the suction of the oem lift pump. With that being said I decided that a pusher was not for me because it just adds one more item to fail, but I would re-design the system that I have , I operate with an auxillary tank 50 gals in the bed of the truck so I plan on plumbing it in as my main supply to the lift, I will also pipe in the return and a seperate gage too, with this setup I will be able to leave the oem pump in its stock location for the heat of the all mighty CUMMINS that is needed in Wyoming, the pump will then get a positive pressure to the suction side and the pump it will have to work less hard = better longivity and reliability. I will then put a small transfer pump on the frame back at the oem tank and use it to transfer fuel as needed to the main feed tank. Also I will have a spin-on filter for 10 microns from the auxillary tank to pick up any forign matter from the supply to keep the screen clean on the lift pump... ... ... Kevin

 

[TPlasek]

Have you ever thought about, with a pusher pump, it is the same amount of work now being performed by two pumps causing it to last longer. The stock lift pump now only has to perform half the work.



I think is is a misconception that cavatation do to sucking from the tank is causing these pumps to fail. I have pulled apart three failed lift pumps in various states of demise. One had 0 psi all the time and the best one would pump 10 at idle and 0 at WOT. In these three cases, the failure occurred in the electric motor portion of the pump and not the pump portion. The brushes and communicator were badly worn in all three cases. The most worn was the 0 psi and the least one was the one that pumps 10 at idle and 0 at WOT.



I still think if you continue to use the stock lift pump alone ,with is design problems, it will fail no matter where you put it.



Anxiety is trying the same thing over and over again expecting to get different results



Here is a picture of the worn communicator on the pump that would pump 10 psi at idle. The brushes even looked worse. (The rust on the bushing surface is due to it sitting in my garage for some time now)

 

[Whitmore]

Yes

I have thought about the oem pump not being the best suited pump for our application , but I feel that giving it head psi instead of a vaccumn will atleast double if not tripple the life of the pump, with my new setup I bet I see a couple psi gained all the way around just from head alone, plus I will be filtering before the pump which will be a plus. I do have plans to monitor the threads here and if the oem pump goes out I will prolly replace it with what I feel is working for others at that time.

I have been bent to find a solution to this crap setup and always knew that pushing the fuel instead of pulling it was the answer and still do, I wanted to install a pump in the tank but cant find the propper one for the application so this is what I have come up with, I feel it will be easier to work on and will have great reliability and service.

I too lost my stock lift pump and replaced it with the Cummins version , it is the same thing only half the price, I tore my old pump down and found that the motor was fine and the problem was the spillback spring had failed and was opening at 4 psi, this gave little to no fuel to supply the VP-44 with adequate supply , cooling and lubricity,

Thanks for your input toward a possitive fix for Dodge's lack of concern of our poor setup... ... ... . Kevin

 

[Rockcrusher]

Too bad we couldn't install the good old fashioned reliable mechanical lift pump. I wonder if there is still a lobe on the cam?

What are the "over the road" rigs using?

 

[WadePatton]

OK, let's forget the pump side and figger on the 'lective side.



(I've fixed a few electric motors with clean up and brushes, but that's about all I know)



Would the brushes/communicator parts wear faster if the pump were working harder? This sounds plausible to me because the current draw would be greater and thus the heat thereby the wear acceleration.



Or are those parts going to wear a given amount per revolution no matter what?







I'm planning to move my pump to the tank area when I mod it. On second pump at 56K now.

 

[tgbol]

Whitmore:

I think you have a good point. I most applications the ISB engine

uses a larger fuel line. The pump is same but Cummins supplies fittings to 5/8 hose. There is a lot less stress on the pump with the larger line.

I performed an autopsy on my when it failed. I found the plastic drive coupling between the shaft and the rotor was broken.

 

[Steve Campbell]

So maybe part of the problem....

comes from these pumps working at their "max" pressure most of the time, thus drawing more "electricity" causing the worn brushes and stator. Also causing the "spillback spring" to open and close more, thus shortening its' life too.



Perhaps a regulator, set on the engine side of the pump, at a lower pressure, with a return line to the tank, would lower the electricity demand (less wear) and not make the spillback spring cycle (less wear), thus lengthening the life of those two components.



Now this does nothing to alleviate the faulty (sucky) positioning of the pump from the Dodge factory.

 

[HVAC]

24v Cam

The cam in our 24v engines does not have a lobe to drove a mechanical pump.



I believe the best transfer pumps (used on big rigs) are electric versions of the internal gear style. They are larger and more durable.

 

[Whitmore]

In my oppinion the spillback or re-circ is not opening while at wot because the fuel demand is heavy to feed the injectors , so with that being said I think the spill back opens while the truck is ideling or at low demand, when my first pump was going out I could watch the pressure fluctuate alot during idle , to me It was the spillback going from open to close and causing it to ossilate or cycle, I think the oem design by Carter is to not dead head the pump and burn it up by overload, also cooling is a factor as well, the pump and all pumps like to keep the fluid moving and transfering the generated heat thru conduction with the process fluids. Now back to my 1st pump while it was failing... ..... when I would put the slightest load on it , it would supply good pressure numbers, thats because the spillback was closed, when I replaced it I tore the old one down and found the spillback spring to be very weak, prolly from all the ossilating it had to do.

When I do install my new system I plan on feeding the oem pump with 5/8 hose, this will give the pump plenty of fuel as supply and then after that it will all be up to the pump itself... ... ... ... ... ... ... ... ... . I think we are getting somewhere now. Kevin

 

[lgibson]

I just had a crazy thought reading this thread. The fuel returning to the tank has some pressure, correct. Is it possible to put a "Y" connector on the return line with one going back to the tank and the other going into another "Y" connector going into the supply line going to the lift pump. Of course both "Y" connectors to be close to the tank. The fuel going into the supply line would go in under some pressure and also help pull fuel into it from the tank.



Any thoughts on this or is it just a crazy ideal. Like I said, This just came to me.

 

[Steve St.Laurent]

The fuel coming out of the VP44 needs to go back to the tank for a while to cool down. I ran on a 5 gallon gas can inside my bed as a temporary tank last spring ( https://www.turbodieselregister.com/forums/showthread.php?s=&threadid=40800&highlight=dot+special ). The ambient temp was 50 degrees. In 10 minutes of easy running (no WOT - didn't want to spill the tank ) the fuel temp in the can was raised from 50 to 105!!

 

[Whitmore]

Steve , I have always wondered what is the flow rate of the return fuel with cassual driving ? also how much at WOT ?



This info could help the quest for improvment of the oem fuel system... ... ... ... ... thanks Kevin



Also if I get the lengths who can custom make me some braided SS lines for my application... ... ..... I live a ways from town and prefer mail order... ... ... . Kevin