I just rebuilt a 24 valve truck, it had the carter lift pump and I did what I thought was right and did the in tank conversion. After that the truck would run out of fuel at 1/2 tank. Took the pump out again and ran it in a bucket with a small amount of fuel and it seems to pump fine. Am I missing something. It runs great when full tank

 

I have installed many of these in tank pumps and never had such a problem. Did you remove the filter screen and look at the check valve at the bottom of the fuel bucket? Possibly stuck or something blocking the opening. When tank is full the fuel will overflow the top of the bucket but when fuel level falls below the bucket is unable to enter fuel bucket. That's the only possible condition that would cause your problem. If you hear fuel pump running when tank is half full and no fuel from outlet of pump. When you put fuel module into bucket did the fuel enter the module from the bottom like it is supposed too? I've seen the ECM not supply power to fuel pump relay after the truck has reached operating temperature. Make sure you have power and ground to fuel pump and you can hear pump running when you lose fuel pressure.

 

Yes the screen looks clean, but when the fuel is below the side of the base cup it can't get enough in from the bottom to keep up but the return fuel is also dumped into the cup so it maintains. I can run the engine from a 5 gal. bucket with 4" of fuel. that is with the pump hotwired. but when I check at the factory wire connection it has 13.5 volts at the pump leads. but the pressure is barely 12 psi and when at a higher rpm drops to 8 psi. this truck has a chip and I know that is not enough pressure.

 

I think we are going to put a FASS system on and see what that does. We also have other trucks with the lift pump conversions that do not seem to have a problem but they do not have this chip.

 

Make sure you install draw straw if you go with a FASS pump. FASS pump will not pull fuel from tank when there is a in tank pump installed.

 

Yes the performance place that sells the system will put the pickup tube in the unit for no charge, because they do so many. Thank you for your help. I hope this is the answer. We had replaced the injection pump and injectors in the rebuild. and I am going to install a gauge to monitor the pressure.

 

Sounds like you are on the right trail...