swenglert

2002 5.9 24 Valve Cummins. Installed a aux filter before my lift pump. Truck started and ran a little, then died. Can't get current to my lift pump. Any suggestions?? Swapped fuel system relays. Checked for voltage at the lift pump connector when the key was turned on and no voltage. Any suggestions would be appreciated. Is there a fuse/relay I don't know about? Fairly new to this truck. Thanks. Shawn

BigIron70

Normal current flow to the pump is 12 amperes.

With the engine running, the pump has 2 modes of operation: Mode 1: 100 percent duty-cycle with a minimum pressure of 10 psi except when the engine is cranking. Mode 2: 15 percent duty-cycle with maximum pressure of 7 psi with the engine cranking

The 15 percent duty-cycle is used to limit injection pump inlet pressure until the engine is running.

The transfer pump is self-priming: When the key is first turned on (without cranking engine), the pump will operate for approximately 1/4 second and then shut off. The pump will also operate for up to 25 seconds after the starter is engaged, and then disengaged and the engine is not running. The pump shuts off immediately if the key is on and the engine stops running.

swenglert

Very helpful. Newer Diesel trucks are a new frontier for me.. History with tractor-type engines and gas engines. Thanks again.
Shawn

CoastalDav

That was some good info on the duty cycle of the pump depending on the mode of operation.

I also noticed on mine that the voltage drops to 9V right after the initial turn on. I assume the computer does that to limit the flow. The voltage comes back up right after start up.

I am on my second replacement lift pump since I've owned my truck. The first on lasted 95,000 miles the second one 86,000 miles and the current one has 6000 miles on it. I've wondered why some trucks have so much trouble with these pumps and others, like me seem to fly for a normal operational cycle. I used to get 75,000 to 80,000 on other electric fuel pumps I installed on past diesel vehicles. So I consider what I've seen with my truck to be a little better that normal. That being said, that Carter in the truck could crap
tomorrow.

I've always wondered if the trucks having problems are running low voltage
and the problem is being created by the computer?

Just a thought.

Dave