m936 no throttle response

[roadagent]

I was running down the road with plenty power then nothing. Came to a stop. Truck will idle at 450/500 RPMs. Press down on throttle and no increase in rpm. Changed filter. Bypassed tank and selector valve by hooking onto fuel canister with 5 psi inline pump running off of fresh 5 gallon bucket. System pressurized easily. Started right up. Same problem of no throttle. Switched back to stock system no change. Looked for fuel pump filter. Either missing or stuck nothing came out when I removed Allen head plug with o-ring on it. Any ideas?

 

[roadagent]

Miserable day east of Indy. Positive side is that I did tow it off I 70 with my Chevy Kodiak. With it idling I had brakes just took awhile for air compressor to build backup.

 

[commandojeff]

Sounds like a throttle cable issue to me. I would say it's the pickup line in the tanks, but you said you bypassed that with no results, so that leaves me to believe it's something simple. Or some kind of air leak in the fuel lines.

 

[roadagent]

Checked out cable and linkage first. Pressurized system from filter up with external pump no FUEL leaks.

 

[Tornadogt]

Sounds like debris in the Injection pump something made it by the filter and stuck in the Injector pump bypass?? bypass stuck open with trash?? just a thought. Try to put a Pressure gauge inline just before the Injector pump and see how much pressure it is maintaining. (not just at idle but when you try to rev. it up)

 

[Smallblockfuelie]

Roadagent, my father was a Cummins mechanic and then later a fuel pump tech. I spoke with him briefly this AM and he said he'd be happy to speak with you on the phone and try to help you trouble shoot it. He is at work right now but leaving tonight to go on a cruise with mother. I'd share his name and work number privately if you'd like.

 

[camp9]

When its idling and you crack the supply line on the injector pump you should get a shower, if not its not pumping enough fuel. If you get a shower crack the return line on the pump and see if any air is coming out. just a thought that might help.

 

[roadagent]

I did crack the line to the pump and it does spray out. I have not cracked the return line. I did empty out 5 gallon bucket of fuel back into the tank when I pulled truck down the shoulder for 5 miles with an external pump running the truck at idle.

 

[wreckerman893]

It may have something to do the the high idle thingy that is used with you are operating the crane or winch. Just a WAG.

 

[camp9]

When you crack the return line it won't run or won't run well when cracked, but you'll be able to see if it's a solid stream of fuel or has bubbles. when it's solid fuel start to tighten it up and you'll hear it fire. Might take a second or two but when it fires tighten it all the way and hopefully you'll be all set.

 

[M35A2-AZ]

There is a little filter on the bottom of the pump on a m936 and on the top a std. m939. It is about 3/4" dia.
Fig. 96 in the parts TM.ARMY TM 9-2320-272-24P-1

 

[Carlo]

Sounds like debris in the Injection pump something made it by the filter and stuck in the Injector pump bypass?? bypass stuck open with trash?? just a thought. Try to put a Pressure gauge inline just before the Injector pump and see how much pressure it is maintaining. (not just at idle but when you try to rev. it up)

Thats a good idea.

 

[Carlo]

I have M931A1 that drove me nuts till I added a 24v fuel pump. My M923A2 has had zero problems. But in your case you did everything I would have done. Now its time to look at the inejection pump. What else is there?

 

[roadagent]

I went back to the truck stop this morning. Truck fired up again this time it acted like rpm increased . Messed around with throttle working back and forth eventually it seemed to work fine. I packed up and it drove 100 miles home. I have know idea what happened. Debris maybe I doubt it was ice becuase it was warm out when my problems started and it has been cold here since. I will be cleaning tanks when warmer outside. First time in 16 yrs I had to leave a vehicle on the road overnight let alone several days. I sure didn't miss it that feeling.
Thanks for all the replies.

 

[Carlo]

I went back to the truck stop this morning. Truck fired up again this time it acted like rpm increased . Messed around with throttle working back and forth eventually it seemed to work fine. I packed up and it drove 100 miles home. I have know idea what happened. Debris maybe I doubt it was ice becuase it was warm out when my problems started and it has been cold here since. I will be cleaning tanks when warmer outside. First time in 16 yrs I had to leave a vehicle on the road overnight let alone several days. I sure didn't miss it that feeling.
Thanks for all the replies.

Do you think it was te min rpms were not high enough?

 

[roadagent]

I was running WOT down the highway when truck returned to an idle. TORNADOGT thought bypass stuck open with debris. I never increased idle. Everything back to normal.......I hope.

 

[Carlo]

I was running WOT down the highway when truck returned to an idle. TORNADOGT thought bypass stuck open with debris. I never increased idle. Everything back to normal.......I hope.

I can of like those auto fix problems but then you wonder will it come back.....

 

[chadande]

I went back to the truck stop this morning. Truck fired up again this time it acted like rpm increased . Messed around with throttle working back and forth eventually it seemed to work fine. I packed up and it drove 100 miles home. I have know idea what happened. Debris maybe I doubt it was ice becuase it was warm out when my problems started and it has been cold here since. I will be cleaning tanks when warmer outside. First time in 16 yrs I had to leave a vehicle on the road overnight let alone several days. I sure didn't miss it that feeling.
Thanks for all the replies.

Glad you got it home!

 

[Smallblockfuelie]

Glad you got it home!

Agreed. Glad to hear it made it home. Hopefully it's a simple fix.

Any pictures of the new rig?

 

[camp9]

Ya, there's nothing like getting your truck home. Glad to hear it. I agree with smallblockfuelie, lets see some pictures