start problem on the 8.3 in my 931A2

[Sambor]

It will seem to lose its prime after sitting for a couple of days not running. I can usually crank it until it starts to hit on a couple of cylinders then it will self bleed and run normal after a couple of minutes. I have tried to pump the primer on the left side, before I start it, but it feels like it is doing nothing. Never worked on a Cummins before, so asking for a little guidance. Thanks, John

 

[Suprman]

You have to open the 8mm screw on the back of the injector pump to prime it. Just go like 2 turns. If you are loosing prime you probably have a leak somewhere and air is getting in. You can put a light pressure like 5psi into the tank one at a time and look for leaks. Also I have heard the tank switch valve has o-rings that can go bad and air can seep in there. Good luck with it.

 

[actionpaintball]

X2...I am betting you have a small leak. Some people have had issues with the pick up tube inside the tank, some have braided lines that have failed, sometimes it can be the primer, a hard line, fitting, filter or select valve. You can make a pressurizing cap or put an air line in the tank and duct tape it up really well. As mentioned, 3-5 psi will work. They also make fuel dye that will illuminate with a black light.

 

[Fredo Corleone]

I had a hose that was cracked on my M931A2 and letting fuel drain back $15.00 at the local truck parts store fixed it.

 

[Sambor]

I didn't know the selector valve had any seals in it-- but that makes sense now. The problem started after I started running on the right tank for the first time since I got the truck. Guess I will pull the valve and reseal it. I thank all of you for your advice. At 60, I feel like I am back in school!

 

[Scrounger]

One way to prime the engine without having to crank so much is to open the bleeder on the bottom of the spin on fuel filter. First pump on the primer, then crack open the fuel bleeder to allow the air out then close bleeder, pump some more then crack open the bleeder then pump away. Once you have the air out of the filter close the bleeder and when one pumps you will hear the fuel going though the injector lines. That will get you going till you can find the air leak.