Cummins 4BT & Diesel Conversions Forums banner
1 - 9 of 9 Posts

·
Registered
Joined
·
1 Posts
Discussion Starter · #1 ·
We're building a custom 1960 Willys Wagon with a 4BT swap. It is on a 2006 Jeep LJ frame/chassis. We are using the stock LJ fuel tank. We installed a 5/8 draw straw in the fuel tank and using the stock frame fuel lines to go up to the engine mounted lift pump. We are using a return fuel line back to the tank.
Our issue is that is loses it's fuel prime and you can't get the engine started. We are having a hard time getting the fuel from the tank to the engine.
I wanted to mount a low pressure lift pump into the fuel tank but that doesn't
Tire Automotive parking light Wheel Sky Vehicle

Vehicle Car Grille Hood Motor vehicle

seem to exist.
Any ideas or advice would be greatly appreciated.
 

·
Registered
Joined
·
1,846 Posts
How is the fuel tank vented? A modern fuel emissions style fuel cap on an older fuel tank can cause internal tank pressure problems.
 

·
Premium Member
Joined
·
1,129 Posts
Does your return line go to the bottom of the tank?
Which lift pump is currently fitted, piston or diaphragm?
Any history on the IP and injectors?
 

·
Registered
Joined
·
1,701 Posts
ON MY Bronco I use an electric pump From the 24 valve motors like maybe a 2000 Dodge tr.. i US THE PUMP THAT CAME STOCK back in the day . Now they've changed to elec. pumps in the fuel tank. I didn't like those pumps . SO I just mounted this elec pump on my frame & It pushes fuel up to the 4BT stock manuel pump . & both then pum on into the Injection pump.
This worked for about 10 years ... Then I got a lot of dirt in my tank.& I had different issues. & About 5 mechanic told me my system wouldn't work . But after I found the rest of the dirt. & then a new injection pump. .i got it running . & I still have the elec 12V. 24 VALVE PUMP on it. & again it's working just like it should.
I like the elec pump because I can prime it before starting .. Cures having an air leak sucking air.
...
......Also I believe you over thinking your situation. as I'm going to say any 12 volt electric pump .. that puts out about 7lb of pressure will // work for you''.
of course you don't want a 33lb or a 40 lb pump . but anything from 3lbs to 10lbs.
 

·
Registered
Joined
·
13,090 Posts
You could also have an air leak allowing you to lose the pump prime. There is a check valve in the line from the lift pump to the fuel filter that should prevent this but if there is a small air leak in the circuit that is negated. The issue of the wrong type fuel tank cap that is mentioned is another possible. Older tanks are vented through the cap where newer ones have a vent hose. On the use of electric lift pump I don't really favor those. The engine is designed to operate without one. Like I mentioned, loss of prime is usually due to an air leak.
 

·
Registered
Joined
·
13,090 Posts
Levis, you have a good point there. 1/2" is usually the largest suction line and that's with a P7100 injection pump. You'd probably only find 5/8" on a modified version of that pump. Normal line would be around 3/8" which is adequate for a VE injection pump which I'm assuming this engine has.
 
1 - 9 of 9 Posts
Top