My brother is building this truck for his son/my nephew. It has a 1994 P-Pump motor with a NV4500. This is the older body style Chevy, since Chevy continued to make Crew Cabs in the older body style even after 1987. The original motor was a fuel injected 350 gasser. Can the lift pump on the CTD be bypassed, and the in-tank fuel pumps be used? Will these in-tank pumps supply enough fuel or too much to the 175 HP P-Pump? The truck has dual tanks, so using the in-tank pumps would be easiest if it will be adequate. The truck will remain stock for only a short time, with probably around 400 hp being the final goal.

 

The TBI pumps only put out around 15 PSI, so not enough for a P-Pump. The good thing is all you need to do is replace the tanks with older gasser units, very cheap and easy to do with the Chebby.

 

Depending on the flow rate of the in tank fuel pumps, you could have it feed the lift pump on the engine. The harder part would be the fuel return from the engine to which tanks. Do the 350 TBI use a return style injection system, or a returnless style?

 

Return, but with a failure, you would be left on the side of the road.

 

Then switch to the second tank, no? How often do those pumps need to be replaced?

 

why would you possibly want to bypass the stock diaphram mechanical lift pump?!?! they're nearly bullet proof, all you have to do is connect a fuel line to it.

 

That's what I was wondering too ??? It's a 12v Cummins, it doesn't need a lift pump from tank.
In theory if you have a 5 speed NV4500 Chevy you should be able to put a CTD in with no problem at all.

 

The motor is in the truck, and almost ready to go. So you guys are saying to just connect the lift pump to the existing fuel system and let the in-tank pumps feed the lift pump? All P-Pump motors have a piston lift pump, not a diaphram lift pump, correct?

 

True, P-pump motors all have a piston pump, which is very reliable. I would not take the chance of feeding it with the electric pump. I would definitely yank the in-tank pump and replace it with a pumpless tank unit. As a technician, I find that the one part that causes the most problem on any vehicle is the electric fuel pump. If they didn't exist, half the towing companies on this continent would disappear. If you don't need this "weak link", get rid of it and don't look back.

 

How does the chev's switch from one tank to the other? Is there a switch valve in the lines, or does it kill one pump in one tank and turn on the other? If its a single tank it would make it dead simple, just put a pickup in the tank and run the line, I'd imagine to keep both tanks, need to go another route? Get the valves they used in the carb'd dual tank trucks instead?