M931a Fuel Issue

[TURKEY131]

I have an M931 that had ran fine until I was out with driving and while I was stopped it began to stall. After several times of it stalling I was able to get it started and began to head back home. Well on the way home it stalled again and I could not get it started again. So after a $300 tow bill I got the truck home.

I suspected a fuel issue and changed the fuel filter. There was a lot of crap in there and I cleaned it real well and replaced the filter with a new one. I got it started again after the filter change. It ran ok for about 30 mins. It seemed to be missing a little bit though. I moved the truck to the side yard and now it sits.

I try to crank it and it just cranks. I am not seeing any white smoke so its not getting fuel. I checked the primer pump and it was hard. I could see the fuel in the line so I knew I was getting fuel up to the injection pump. I cracked the line on the top of the fuel cut off and I could see fuel in there. When I left the line off and cranked the motor I did not see any fuel coming out of the pump.

I am looking for some ideas, could it be the injection pump?

 

[wrenchturner6238]

Just a thought here. You might check to make sure you are getting voltage to the fuel solenoid if you are getting power to it turn in the fuel screw on the front of the solenoid. Not sure if you know the screw i am talking about it is a thumb screw in the front of solenoid just below the out put fuel line. This puts it in manual and it will not shut off until you back the screw out. It is something to try.

 

[TURKEY131]

Wrenchturner I know the screw that you are talking about. So I need to turn the screw in?

 

[wrenchturner6238]

Yes turn in the screw and give it a shot. If it starts ok then you will likely have to replace the solenoid. Some of the guy's talk like the tank switching valve gives trouble on these tractors by sucking air but i am not sure you are sucking air into the fuel.

 

[TURKEY131]

Wrenchturner thanks I will give it a shot.

 

[TURKEY131]

(UPDATE) Well today I tried turning the screw as far in as it would go. I am still getting the same results. Although I did crack the fuel line but I still am not seeing the white smoke from the exhaust. Is my ejector pump bad? What else can I do?

 

[wreckerman893]

If you have the 8.3 Cummins are you making sure the fuel shutoff solenoid is working. This has been a persistent problem with these trucks since they were fielded. The silver nub at the bottom left of the solenoid should retract when you turn on the battery switch. If it doesn't retract then the fuel will be shut off. If it is not retracting you can rotate the lever and zip tie it open or if you have a "Soldier B" get him to hold it open while you are cranking the engine. You may also have to prime the fuel system using the hand primer located to the right and down from the solenoid. Pump until you hear a squishing sound from the injector pump.

 

[TURKEY131]

wreckerman893, I have the older 250.

 

[wrenchturner6238]

You may want to take the sensor out of the top of the fuel pump (it has like 4 wires to the sensor and it's a 1/4" pipe fitting) and look in there and see if you see fuel if you do not see any or fuel does not run out pour some clean fuel into that port ( this is where I would put in fuel after I installed an rebuilt pump to help getting the fuel system primed up). I think you have sucked some air or lost prime some how. I would take the return line off as well while cranking you should get some returns. If you pump is low on fuel start taking items out of the line up untill on the suction side (after you get running) to see where you are getting air (Get another bucket with clean fuel in it and run you suction out of the bucket) eliminate components in the suction until your returns are clear of air. I hope this makes since it keeps logging me out while i am trying to type and think.

 

[TURKEY131]

Wrenchturner, I think I got it. I'll give it a try tomorrow. Thanks!

 

[capnkirk]

FWIW, I picked up my 923A2 from Leonard Wood and had fuel starvation issues from the start. Ended up replacing filter and bypassing tank. Cut line before filter and ran to tank in bed (also reroute return line). Got it home where I could work on it and discovered I couldn't get fuel from the tank with a hand squeeze bulb pump. Ran the hand pump backwards and had resistance due to an obstruction. Kept pumping until I blew it loose. Drained tank. Refilled with new fuel and good to go.

 

[ARYankee]

Check your rubber fuel lines. A lot of times they are dry rotted or cracked and suck air. They can also become so brittle that they collapse under any load. It's a cheap and fairly easy fix.

 

[TURKEY131]

Aryankee, I visually checked the fuel lines. They looked good and fairly new. My primer pump has a good prime and I can still see the fuel in the lines.

 

[Jeepsinker]

Do you have the large filter canister in the wheel well behind the driver side steer tire? If so, get a 1/2" to 1/2" male to male brass fitting and bypass it, then try again. Also pull the fuel line off directly before it enters the injection pump and put some air pressure to the fuel tank. Be careful not to put too much air pressure in there. Put pressure for a few seconds, then let settle, then pressure, then settle. But don't let the tank lose all the pressure for so long that the fuel drains back out of the lines. I hope you know what I mean. It would be so much easier to show you.

 

[TURKEY131]

Jeepsinker, Is this to see if there is any leaks?

 

[Jeepsinker]

Yeah. Do it with the power switches on and that screw on the solenoid turned all the way in. If you end up getting fuel from the line by the injector pump then you know that your problem is that you are sucking air somewhere and that should make the problem evident one way or another. If you don't get any fuel then you have a blockage in the line somewhere. You may try taking the line off before the fuel shutoff as well, see if you get fuel there, if you do then reconnect line there and try again to see if solenoid has a blockage in it.

 

[TURKEY131]

Well after not having any time to work on the truck I had a little bit of time today. I pulled the large fuel line that connects to the injection pump and it is full of fuel. I removed the fuel sensor and topped it off with fuel and removed the fuel line going into the top of the fuel cut off switch. I turned the screw all the way in and cranked the motor, I did not get any fuel coming out of the fuel cut off switch. Could the injection pump go bad all of the sudden? Any ideas?

 

[wrenchturner6238]

I would check the drive couple on the shaft of the fuel pump it could have gotten loose and now spinning on the shaft. I have seen the air compressor drive adapter brake as well.

 

[TURKEY131]

I tried pumping the primer pump again and I was getting alot of fuel coming out of the handle as I pumped it. Is this normal?

 

[wrenchturner6238]

You should not get fuel coming out of the handle shaft. That could be a source of getting air in the suction of the pump.