Attention: TDR Forum Junkies 
OK, I have this theory concerning lift pumps used in our trucks...
The primary mystery to me has revolved around the fact that most pumps live a relatively normal lifespan - I have no particular complaint about a LP failing at 80,000 miles or more - but AM puzzled at those cases where a guy has repeated, multiple failures within 30,000 or so!
Could these pumps REALLY be that poorly designed and manufactured? My common sense and disassembly of sample pumps tell me NO - that after you allow for that small but inevitable number of cases where defects DO occur, some other factor must be at work - and here's what *I* think is happening.
I think there IS a poor design problem relative to the LP - but NOT the pump, but the CONNECTORS selected and used by DC to power them! Careful inspection of these connectors tells me they simply are NOT capable of carrying the needed amount of current the pump requires under full load. Sure, if all is perfect, and a GOOD full surface connection is obtained and maintained in that connector, it will probably last - but a poor or degraded connection will sacrifice current flow, cause intermittent or erratic pump operation, and possibly damage the pump itself due to long term low-current operation.
SOOoo, guy takes his "failed" LP to the dealer, who verifies low pump pressure, and installs a new pump - lo and behold, all is well - for a little while! The act of unplugging to old pump, and plugging in the new one restores some of the corroded/damaged contact area inside the engine side of the pump plug, and at least for a while, provides a completely new contact area on the pump side - until more miles and use repeat the pitting/erosion of contact all over again!
Eventually, the owner gets disgusted with the stock setup, and perhaps adds a pusher pump - then all seems well - so guy figures THAT was what was really needed - it undoubtedly helps, but maybe not entirely for the assumed reason! The new pusher pump assists the stock LP, and reduces total pump load and current draw - pulling that current draw down to a level the lousy DC power connector can now handle in a reasonable fashion...
The same may hold true for these other fancy fuel systems popping up for sale for our trucks - they probably ARE a better fuel system than the stocker - but *I* would bet their GREATEST advantage would be use of better connectors than what DC provides as stock equipment for these trucks.
For reference, the connectors used for various low-current sensors on my old ‘91 frequently went bad a well, resulting in low/no oil pressure readings, etc. , and always returned to normal after a thorough cleaning of the plug - and they were the same type plug used on the LP's on our trucks!
I had a LP problem on my own truck last trip out with our RV - replaced the pump with my backup, but carefully inspected the plug pins on the "failed" LP itself, and with a magnifying glass saw evidence of pitting that is typical of what I am talking about - pressure testing of the LP itself out of the truck after disassembly revealed no discernable mechanical problems, showed the pump to functioning perfectly - so it is now my spare!
IF this problem reoccurs, I will permanently solder leads directly to the LP, seal them with RTV, and convert to a larger, more reliable connector capable of greater current - and junk what DC has provided...
Just FYI - and food for thought...
The primary mystery to me has revolved around the fact that most pumps live a relatively normal lifespan - I have no particular complaint about a LP failing at 80,000 miles or more - but AM puzzled at those cases where a guy has repeated, multiple failures within 30,000 or so!
Could these pumps REALLY be that poorly designed and manufactured? My common sense and disassembly of sample pumps tell me NO - that after you allow for that small but inevitable number of cases where defects DO occur, some other factor must be at work - and here's what *I* think is happening.
I think there IS a poor design problem relative to the LP - but NOT the pump, but the CONNECTORS selected and used by DC to power them! Careful inspection of these connectors tells me they simply are NOT capable of carrying the needed amount of current the pump requires under full load. Sure, if all is perfect, and a GOOD full surface connection is obtained and maintained in that connector, it will probably last - but a poor or degraded connection will sacrifice current flow, cause intermittent or erratic pump operation, and possibly damage the pump itself due to long term low-current operation.
SOOoo, guy takes his "failed" LP to the dealer, who verifies low pump pressure, and installs a new pump - lo and behold, all is well - for a little while! The act of unplugging to old pump, and plugging in the new one restores some of the corroded/damaged contact area inside the engine side of the pump plug, and at least for a while, provides a completely new contact area on the pump side - until more miles and use repeat the pitting/erosion of contact all over again!
Eventually, the owner gets disgusted with the stock setup, and perhaps adds a pusher pump - then all seems well - so guy figures THAT was what was really needed - it undoubtedly helps, but maybe not entirely for the assumed reason! The new pusher pump assists the stock LP, and reduces total pump load and current draw - pulling that current draw down to a level the lousy DC power connector can now handle in a reasonable fashion...
The same may hold true for these other fancy fuel systems popping up for sale for our trucks - they probably ARE a better fuel system than the stocker - but *I* would bet their GREATEST advantage would be use of better connectors than what DC provides as stock equipment for these trucks.
For reference, the connectors used for various low-current sensors on my old ‘91 frequently went bad a well, resulting in low/no oil pressure readings, etc. , and always returned to normal after a thorough cleaning of the plug - and they were the same type plug used on the LP's on our trucks!
I had a LP problem on my own truck last trip out with our RV - replaced the pump with my backup, but carefully inspected the plug pins on the "failed" LP itself, and with a magnifying glass saw evidence of pitting that is typical of what I am talking about - pressure testing of the LP itself out of the truck after disassembly revealed no discernable mechanical problems, showed the pump to functioning perfectly - so it is now my spare!
IF this problem reoccurs, I will permanently solder leads directly to the LP, seal them with RTV, and convert to a larger, more reliable connector capable of greater current - and junk what DC has provided...
Just FYI - and food for thought...
