PDA

View Full Version : 4320 lift pump pressure?


Cummins Driver
06-12-2009, 02:56 PM
Hey guys. Dad has an old 4320. We have had it for a little while. It ran fine when we got it aside from a little blowby, but now, you can start it, and it will hardly idle. It sputters, misses, and puffs black smoke, and will normally die after running it a little. Im pretty sure the lift pump is just shot. We changed the fuel filter, and primed it the best we could and it started and ran good for a minute, and then went back to having no power and barely running.

So today, I took my fuel pressure gauge, and pulled the bleed screw out of the fuel filter housing, and threaded the line to my gauge into it. I fired it up, and its only showing between 0 and 10psi no matter what RPM, and it is very erratic. The needle bounces up and down the whole time. I need a needle valve to stick on it to calm down the pulses, but I still think the lift pump is probably shot.

Im not sure what the factory specs are on fuel pressure. If anyone can help me out with the factory specs, I would appreciate it. Thanks

Eric

KTA-Cummins
06-21-2009, 02:52 PM
About 4-6psi is enough.

Cummins Driver
06-23-2009, 11:52 PM
Hmm, wish i knew that a couple days ago! haha

Anyways, we put the new lift pump on it, and no change in how it runs. Dad said when he cracked the bleeder screw on the pump that it would run fine then?? Any ideas what the problem could be?

Eric

BlackSkyRacing
06-30-2009, 11:48 AM
Your fuel line from your tank to the lift pump may have a pinhole in it allowing air to be pulled into the fuel. Try taking inlet line off the lift pump and find a way to get a fuel source above the lift pump.

JDGnut
06-30-2009, 11:35 PM
Also check your return line, and make sure it is free... cann't remember the model.. but there were some issues with a check valve in the return line... usually just removed it.. and it was back to normal..
Good Luck,
Bryan