Engine/Transmission (1998.5 - 2002) Dead lift pump an obstruction?

[jstyer]

Lift pump went dead many moons ago. Put in carter push pump but left fuel going through original lift pump. Is the original lift pump an obstrution? Should I bypass lift pump and if so what is the easiest way - plumbing wise and electrical wise? With Carter pump I cruise -on level ground- at approx. 15 psi and 18+ at idle. At WOT it jumps way back to 8-9 psi.

Thanks

John Styer

 

[HoleshotHolset]

Put in carter push pump but left fuel going through original lift pump. Is the original lift pump an obstrution? Should I bypass lift pump and if so what is the easiest way - plumbing wise and electrical wise?

It has been a long standing thought in my head that you can't push through a dead fuel pump. I'll keep that thought unless someone offers some opposing information.



You can make bypassing your OEM lift pump as simple or as complicated as you want. Some folks do nothing more than disconnect the lines (plugging them up to keep road jerky out... ) and tape up the wires so that they don't corrode and so that the hot lead doesn't short out. Other folks have written a dissertation on the proper way to get rid of the OEM lift pump.



This is the one modification that really does deserve a BOMB... like C4 or TNT. Those OEM lift pumps are HORRIBLE.



Matt

 

[Loren]

I also thought that you couldn't push fuel past a dead pump, until it happened to me.



I have a booster pump installed to feed the engine-mounted lift pump. The wire to the engine-mounted pump parted, killing it. The truck would run at VERY low RPM's and would not pull hard, but it would run. I was able to limp to a parking lot while pulling a trailer in this configuration.



I am sure that if I had had some way to bypass the engine-mounted pump the truck would have run fine on the boost pump installed in the fuel line.



I finally found the parted wire and jury-rigged a repair that worked until I got home and could fix it correctly.



Loren

 

[Steve St.Laurent]

My engine mounted lift pump died on me a couple weeks ago and my 7 psi pusher pushed fuel through it no problem. It all depends on how the pump fails.

 

[mhenon]

pushing fuel

The vanes in the stock lift pump are sort of free floating in the rotor assembly. I've taken a LP apart and think fuel would by-pass easily if the pump went dead. The incoming fuel would push it's way past one or two vanes and re-seat them, leaving a clear path (somewhat) for fuel flow.

This is probably why some people are running on a dead LP and the VP is just sucking fuel right through it.

Mike