Cooker .308

Have a 94 12valve works fine for awhile then when you take your foot off the pedal she quits. Starts right back up, hold her at 2000rpm, holds for a bit then just fades away. Would like to know how to take OFV apart to check spring, am I on the right track?

clutch1

you might be either sucking air or running out of fuel. check lines

schoust

Absolutly,time for some new lines. I fyou do a search there are many thread that talk about the replacing of all the lines supply and return....

Cooker .308

New lines right from tank to lift pump, new lift pump, new fuel cutoff silinoid, none of these repairs helped same problem I started with.

clutch1

so it runs then shuts off every time? after it shuts off can you imediatly start it back up and it'll run fine for a while or do you have to wait? the overflow valve is in the return banjo bolt right next to the head dont loose the spring or ball seems the spring would have to be completly gone to effect it that much though.

tony597fitter

Did you replace the 2 gaskets on the fuel prefilter? Mine were really dryrotted. The prefilter screen kit is $8.00 from cummins, but you will need another gasket for the fuel heater element. Same gasket as the one that comes in the prefilter screen.
Also I have heard the fuel heater harness can leak over time.
The overflow valve is on the left side of the pump, looking at it from the front. It might be a one piece unit. If its a two piece you can take it apart and stretch the spring a little bit. You can get a new overflow valve from Precision deisel. Search for Marty Thompkins?. $35 from them.
TST also sells them.
There is also a way to test the overflow valve. Just do a search.

Cooker .308

Clutch :. Starts right up again, hold her at 2000 rpm, runs for a minute then just fades away, you can do this as many times as you like.I am doing this parked in the drive. I understand now my OFV is a one piece unit.

schoust

Did you take a real good look at the tank module when you replaced the lines I have heard that thdrops can develope pin holes causing these types of issues,do you have a fuel presure gauge?

clutch1

will it run without holding the rpms up? try running fuel from a gallon jug to the lift pump just to rule out the tank and lines the return line isnt pinched off? and im sure filters have been changed. when did it start doing this?

clutch1

how much fuel comes out of the bleed screw while pushing hand pump?

coastal_diesel

I got an overfow valve from the Cummins dealer for my 98 12 valve and it was only 8.50. If you need a part try to get it from them. Actually you can get in touch with me via pm.

One other thing, my truck had a recall regarding the throttle linkage. When I brought her in for a return line replacement, the recall came up in their computer system. They replaced the bell crank amongst other things. Perhaps your truck has a throttle linkage problem

tony597fitter

By any chance when you replaced the lift pump did you use 2 gaskets? When I did my lift pump they only send you one gasket. You actually need 2. One for the block to prefilter mount and one for the prefilter mount to the lift pump.
Its stupid that they only give you one gasket. I got the other one at cummins for under $2.00.
Maybe your getting air.
Just a suggestion.