Guest

A while back, I asked members for any of their old Lift Pumps they would be willing to part with for an experiment and autopsy to see if apparent defects existed, or possible repairs could be made to return them to service.

Unfortunately, I only found 2 fellas who helped - and so instead, I have decided to limit my efforts to simply providing a visual presentation of how the stock Carter lift pumps are constructed, and what the condition was of internal components of one older pump that made it to over 100,000 miles, and was replaced only as a precaution, even tho' it was still functioning properly - the second pump is fairly new, and was replaced because it was thought that the fuel pressure was falling off below specs.

This may help some diesel newbies who don't yet know what a lift pump is, or looks like - it is a fuel pump designed to provide flow and fuel pressure to the Cummins VP-44 fuel injection pump - the VP-44 needs to be provided with a decent minimal positive PSI, usually accepted to be no less than about 8 PSI at the inlet to the injection pump.

Here's a pic of the pump - it's shown upside-down here, compared to its normal mounting position on the Cummins.

Other pics down below...

Guest

Here's the pump with the bottom plate removed, exposing the rotor and vanes of the pump itself - the rotor and vanes look to be made of stainless steel - the outer housing of the pump is pot metal or similar, and there is what appears to be a stainless liner that the vanes are in physical contact with - the top and bottom plate of the pump also appear to be of stainless steel. The vanes are not spring loaded to force them against the outer walls of the pump chamber, but rely on centrifical force to make and hold contact and provide pumping action.

The circular disc seen attached to the pump cover gasket fits into the recess above the pump rotor, and is tightly held in place to provide both a seal and wear surface for the rotor and vanes.

Guest

Here's a closer view of the pump body showing the rotor and vanes - and also the fine mesh stainless steel screen that provides some protection against larger impurities that might damage the pump.

Guest

Here's the rotor and vanes removed from the pump housing - and showing the slotted shaft that mates with a corresponding recess in a nylon insert in the pump rotor for connection to the motor armature - this has been a relatively common source of failure, when either wear or excessive torque damage that connection, causing the pump to fail.

Again, the vanes themselves simply "float" in their respectice slots in the pump rotor.

Guest

Here's an overview of both pumps used here - the one on the left is the high-mileage one, disassembled...

Guest

Other than the removal of the pump cover shown earlier, there are no other user-serviceable parts to these pumps - the motor cannot be disassembled without destroying it.

The outer motor housing is crimped onto the pump housing, and employs a neoprene gasket to prevent leakage.

Here, the motor armature and upper part of the pump housing can be seen - at the left, inside the housing, you can see the pressure relief ball/spring/seat assembly - on these pumps, pressure is set at about 15 PSI. This valve appears to be in excellent condition.

The armature, while obviously used, is in excellent condition - there are visible signs of polishing, or wear at the bushing points on the armature shaft - but by no means excessive. and the bushings seemed good as well.

It's worth pointing out for those unfamiliar with these pumps, fuel actually flows THRU these pump motors in normal operation whenever the pressure valve is open - and any metal or carbon particles wearing off the motor components eventually end up in the Cummins fuel filter!

Sorta makes you wonder if lack of internal fuel flow in the LP during times when engine demand pulls it's delivery PSI below 15 PSI or so might be a factor in early LP failure...

Guest

And here's a shot down inside the motor itself - the green assembly at the far end is a noise filter circuit board assembly to dampen the arcing noise common to DC motors from the brushes and commutator.

Note that even with over 100,000 miles, the brushes still are in EXCELLENT condition, and would likely go another 100K!

Guest

... So what did I learn from all his?

WELL, *I* learned that unless there is some external contributing factor, these pumps ARE capable of long term reliable operation - I learned that since they, like the VP-44, rely upon a decent INTERNAL flow of fuel for cooling and lubrication, the addition I have done of a pusher pump MIGHT help that internal fuel flow and lube - my PSI *never* falls below 16 psi, even under the worse case scenario - which SHOULD mean there is a constant internal fuel flow inside the stock LP even during those periods...

The fuel additives and extra fuel filtering I have added to my fuel system should assure that only the cleanest possible fuel gets thru my added pusher pump, and the stock LP... But even with all the filtering PRIOR to the stock LP, keep in mind that ALL the inevitable wear particles INSIDE that stock LP *will* end up passing on THRU the pump, and with the EXTREMELY close tolerances of the VP-44, we can fully appreciate the importance of a GOOD quality final fuel filter in the fuel flow - and the extreme care that must be used on filter changes to insure that contaminated fuel does NOT get passed on to the VP-44!

Personally, *I* would prefer a pump that did NOT pass its wear garbage on thru so sensitive a fuel delivery system - seems like asking for trouble!

NOW, all I can do is wait and see how well MY setup holds up... ;D ;D

Guest

[quote author=BigBlue link=board=4;threadid=16913;start=0#158533 date=1057873138]
So Gary. Which one of those pumps was mine? That's interesting stuff. The pump I sent you had maybe 400 or so miles on it. I got it brand new from Dodge and the pressures were 13 at idle and 6 at WOT. >
[/quote]

Yours was the one up at the beginning, showing only the pump portions - it runs fine and showed virtually NO wear in the pump area at least - I didn't want to totally destroy a good pump - so only dismantled the older pump that didn't come with the pump components, since the owner of that pump had already taken it apart and lost the internals...

Later, I will test run your pump with guages to see what PSI and volume it will deliver, and probably keep it around as a usable spare...