Attention: TDR Forum Junkies 
Just as FYI for those who havent done this...
I took my original (as far as I know) lift pump off my 99 2500 and replaced it a couple of days ago, as some of you may know it would simply not refill the filter cannister after I changed filters.
Being curious about it (its a Carter of some type), I took the top plate off and got my first look at its internals. Top plate, rubber gasket, intake screen, impeller plate... thats about it. Basically the motor spins a round hub with sliding blades that rub up against the walls of its housing. These blades are centrifugually forced against the housing which draws fuel in and takes it around where the housing narrows and its forced out the discharge. Looks like if the discharge line is blocked (flow stopped or slowed), the fuel can go down a port in the discharge, around the bottom of the pump and through a spring loaded relief back into the intake side of the impeller.
The inside was completely clean. Not one spec of anything in the screen or anywhere. Geez, I really cant see why in the world this thing fails. If ever a simple component existed, this is it. I mean I really can't see why they would give up so easily.
The only thing is that maybe the relief spring weakens and all it wants to do is bypass pump around itself. Or maybe the sliding impeller blades somehow loose their scraping edge and cant seal up against the round impeller housing and create any pumping pressure. Or the electric motor wears out somehow.
I bet the spring weakens and it cant build up pressure to overcome the air in the system during filter changes. Which is maybe what happens over time as they loose ability to make pressure. Fire pumps have relief valves just like this but they are adjustable so I can determine the max output pressure and adjust it according to conditions. Otherwise, it dont get the high failure rate. I think Im gonna build a bench model to see if this thing works and how much pressure I can get out of it. But the motor and bottom of the pump looks sealed. Dang.
I took my original (as far as I know) lift pump off my 99 2500 and replaced it a couple of days ago, as some of you may know it would simply not refill the filter cannister after I changed filters.
Being curious about it (its a Carter of some type), I took the top plate off and got my first look at its internals. Top plate, rubber gasket, intake screen, impeller plate... thats about it. Basically the motor spins a round hub with sliding blades that rub up against the walls of its housing. These blades are centrifugually forced against the housing which draws fuel in and takes it around where the housing narrows and its forced out the discharge. Looks like if the discharge line is blocked (flow stopped or slowed), the fuel can go down a port in the discharge, around the bottom of the pump and through a spring loaded relief back into the intake side of the impeller.
The inside was completely clean. Not one spec of anything in the screen or anywhere. Geez, I really cant see why in the world this thing fails. If ever a simple component existed, this is it. I mean I really can't see why they would give up so easily.
The only thing is that maybe the relief spring weakens and all it wants to do is bypass pump around itself. Or maybe the sliding impeller blades somehow loose their scraping edge and cant seal up against the round impeller housing and create any pumping pressure. Or the electric motor wears out somehow.
I bet the spring weakens and it cant build up pressure to overcome the air in the system during filter changes. Which is maybe what happens over time as they loose ability to make pressure. Fire pumps have relief valves just like this but they are adjustable so I can determine the max output pressure and adjust it according to conditions. Otherwise, it dont get the high failure rate. I think Im gonna build a bench model to see if this thing works and how much pressure I can get out of it. But the motor and bottom of the pump looks sealed. Dang.
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