I went through an in-tank fuel pump dilema last summer and finally ended up buying a new pump from Omympic Controls for approx $225.00.
The in-line carter (and others) thumper pumps work but they don't have the capacity called for in the TMs. According to the TMs, for the milti to produce maximum power, the in-tank pump is suppose to deliver (if memory serves me properly) 3 to 7 PSI of pressure to the injector booster pump.
I've got fuel presure gauges before and after the primary fuel filter. With the in-tank pump off and the thumper pump running my fuel pressure drops to zero when I start the engine. In other words, is doesn't deliver a positive flow to the IP booster pump.
With the in-line thumper pump shut off and bypassed and the new Olympic Controls pump running I get 3 -5 PSI positive pressure. I've still got both pumps installed therefore I can switch back and forth. This sumer I'm going to remove the in-line thumper pump.
Before I found Olympic Controls I purchased two supposedly good used "previously inspected" in-tank pumps from reputable dealers. Both were junk! Neither lasted over a week! The first dealer returned my money, the second did not therfore I took a $200.00 bath. The closest the second pump ever got to being "checked out" was perhaps it ran when taken out of the original truck. It took my 30 minutes to pry the fuse cover off the top cover plate.
I wouldn't touch a used in-tank pump with a ten-foot pole.
I've had people tell me that the in-tank pump is only for getting fuel to the engine so it will start --- that after start-up the pump isn't needed. That's not what the TM says.
I also question how an in-line thumper would work with WMO.
Go to Olympic Controls and you won't have to worry.
