Why lift pumps fail

[dmurdock]

Icarus33 posted some pics of a dissected lift pump, one of which i've attached. I've heard all the fuss about failing liftpumps, but never "what" exactly failed. Is it the motor? Or is it when the pump quits putting out the proper pressure/volume, it is considered failed. The reason I ask is something I remembered while looking at the attached picture. I had an old hot rod that had a holley "blue"(i think) pump which at that time was there "bad boy". It was the same type of pump, but there was one major difference in the design. On the holley, the sliding "rotors" or "vanes" or whatever you call them were exactly 90 degrees to wall of the pump. I appears that the carters "vanes" are around 45 degrees or so, thus a lot of the centrifugal force of the spinning rotor is pushing the vane against it's "carrier" instead of out agains the edge of the pump. I'm just wondering if these failures are due to vanes "sticking", thus dropping the pumps overall capacity. I can see how even 1 sticking vane would cause a huge problem.



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[HVAC]

Good Eye

I was going to point that out and I'm glad you did. The vane configuration on the Carter is different then any other pump I've taken apart. It's sort of a swastika layout. My Holley and the others have a very perpenticular angle to the chamber wall. Even the 2" pump I overhauled off a semi truck had vanes that were perpendicular to the sleeve wall the rotor spum within. That's a good point.

 

[RustyTRanch]

I want to know if it is the pump failing or the motor.

We use hydraulic vane pumps on all our eqiupment and the pumps fail now and then. Most of the time the cause is dirt that gets in the oil and scares the surfaces of the pump. we rebuild the pumps. Someone talk about a pre lift pump filter it might be a thought if the pump is the part that fails.

later

mike