Engine/Transmission (1998.5 - 2002) Lift pump internals

[fmj]

Still a lot of talk on these lately. I've never seen the inside of one and was curious as to what craps out. I was surprised to see there is not much to "wear" from a mechanical point. The electric motor, brushes, etc. aren't something that wears out in mileage we see these crapping out. The one shown below had 60k on it and pressure was floating from 14 lbs down to 9lbs while crusing at 70mph. Since I was going on a trip towing, I didn't want to chance it going out while I out in east nowhere. I just changed the second one as it was acting up the same way, it has 70k on it. I also just ordered a BD's version of pusher. Anyway, for those of us that never seen the inside of one here goes.

 

[fmj]

You will note that the picture of the pc board on bottom of case that has + and - wires coming from it have two small resistors and transistors. I checked the resistance between the pos and neg wires and it is 3. 0 ohms. Not sure if thats what a good one has or not.

 

[Gary - K7GLD]

AH, reinventing the wheel - a search "lift pump" on this board would point to THIS:



https://www.turbodieselregister.com...ion-1998-5-2002/108275-anatomy-lift-pump.html

 

[Gary - K7GLD]

... and that circuit board you show is a spark/arc suppressor, to eliminate static in radio receivers and such...

 

[rweis]

There are miles of threads about the internals of the lp.



To mention a few:



Internal check valve ball not seating, damaged seat, bad spring, not centered.



Small nylon connector at the top of the armature that fits into the vane pump hub damaged. slips, does not seat properly.



Cavitation problems in conditions when there is little actual flow, like at idle, THEN not able to clear the cavitation when fuel demand resumes.



Actual motor failure, poor design of wire harness especially in high corrosion environments.



Design of the motor is not designed to work as a suction pump (ie where it is mounted on the engine). Engine vibration and heat not conducive to consistent smooth lp operation.



Marginal design (psi, volume) to feed the VP44 properly in the first place over a long period of time.



Vane pump vanes not spring loaded to ensure pump cavity contact, pump vane can stick in the paritally retracted position.



And there are lots of other concerns not addressed above.



Just some ideas,



A search would be a good first cut on lp problems,



Bob Weis

 

[fmj]

RATS! You even take better pictures than me. Oh well, at least I got to touch and feel. I wanted to see if there was evidence of "wear" in the internals. Found nothing. I knew I'd seen and exploded view quite a while ago, but when I did a search I entered "lift pump" and got lots of verbal about failure. Should have narrowed the search by typing right words.

 

[Gary - K7GLD]

RATS! You even take better pictures than me. Oh well, at least I got to touch and feel. I wanted to see if there was evidence of "wear" in the internals. Found nothing. I knew I'd seen and exploded view quite a while ago, but when I did a search I entered "lift pump" and got lots of verbal about failure. Should have narrowed the search by typing right words.

Hey - no problem - all part of learning new stuff - dunno if you caught it in the article I posted, but the pump pictured had over 100K miles on it, and was still operating fine - the owner just wanted to swap it out as a maintenance item!

 

[fmj]

ya gary i caught that on the write up. this one had 60k on it as i mentioned, but since it was acting quirky by running and then dropping while not changing speed or rpm, i also changed it out rather than take a chance of changing in the middle of nowhere at 110f outside. i also thought that it might be filter, although i change them between 7 and 10k, or a pressure sending unit so i used my mechanical gage on both pre and post filter. got no pressure drop on pre/post and gages matched. the auxiliary pusher pump will give me piece of mind.

 

[icman95]

I'm glad to read that someone else had a pump operating erratically at 60k miles. About a year and a half ago I had my truck in the dealer for something else and asked them to check the flow/pressure specs of the pump even though nothing seemed wrong. They were confused as to why I was asking on a truck that only had about 60k on it. I told them what people on the TDR have experienced and the very next thing the service manager said was "What's the TDR?" I knew I was in trouble at that point. He pretended to not know anything about lift pump problems but agreed to run the test anyway. Turns out I was right. It was only putting out about half the pressure and volume that the spec called for. At this point he tried to sell me the in tank replacement and said they no longer make this pump. I had already called to the local Cummins dealer and found 4 sitting on their shelf. I ran down to get one and the dealer put it in for me. He was quite surprised. Maybe he should start reading the TDR. Fixed the whole problem, now with the FASS pump. Bye, bye crappy lift pump!