So I Had to Use the Emergency Engine Stop Control Today...

[wbread99]

This was a new one for me today. Pulled my 923A2 into the commissary parking lot today, and when I turned off the ignition switch, the truck continued to run. Never flinched. Hmm I say. Interesting.

Put the ignition back into run position and drove to our abandoned flightline, thinking if anything resulted in fireworks, it wouldn't be at the commissary. Truck seemed to be sluggish but that may have been me overthinking things.

After several attempts to stop the engine the normal way, I yank the emergency stop lever out and it quits immediately. Humph, I think. That was easy. So then I start the truck and try to replicate and I can't. Shuts off every time.

I'm thinking the only thing that can cause this is the fuel pump circuit from the ignition, or the ignition switch itself. Thinking some contact cleaner in the switch might help.

Anyone have a similar experience or some insight?

 

[Jeepsinker]

The shutdown solenoid is crapping out. They are expensive. I would run it until it quits, then throw it away and just use the stop cable. Usually they fail in the off position and cause a no start.

 

[The HUlk]

Sometimes after pulling the stop cable the lever that it actuates which cuts off the fuel supply sticks in the closed position. Pushing the cable does not reset the lever position. I had to open the hood and push the lever back by hand. Mine's an A1 NHC250 and it's on the drivers side forward of the hand primer pump area. Having soldier B activate the cable made it a breeze to figure out.

 

[goldneagle]

Yep the Emergency Kill lever on the 5 tons do not rest themselves by pushing the lever back in like on the Deuce. You have to go under the hood and reset it there.

 

[doghead]

Soldier b should have read the operators manual to you.

 

[98G]

I've seen a lot of A0 and A1 with a second stop on the cable that allows it to reset from the cab. And as Jeepsinker adds below, this is an A2 and they do reset from the cab...

OP never said he couldn't get it to restart. . .

 

[Jeepsinker]

This is an A2, not an A1. The shutoff does reset itself on the A2, even after the cable is pulled.

 

[goldneagle]

This is an A2, not an A1. The shutoff does reset itself on the A2, even after the cable is pulled.

Sorry I didn't know that! Never driven or owned an A2 M939 truck.

 

[Floridianson]

The shutdown solenoid is crapping out. They are expensive. I would run it until it quits, then throw it away and just use the stop cable. Usually they fail in the off position and cause a no start.

Thought it is really a run solenoid and when it get power it holds the IP open in the idle position so it is needs to be there and can not be removed if bad just replaced. Could the shaft of the solenoid sticking and lube make a difference. Think I might try some WD40 on it and see if it ever does it again. If that is your only problem with the truck for awhile you should feel lucky.

 

[Suprman]

With the truck off, hand push the solenoid in and feel how it pushes back out. See if it's binding. Push the solenoid in and hand move the fuel control on the ip and see if that's binding. The fuel control on the ip is connected to and slides across the emergency cut cable. Sometimes if the cable is kinked the fuel control on the ip can get stuck on it. It's an easy fix.
Will

 

[Jeepsinker]

Thought it is really a run solenoid and when it get power it holds the IP open in the idle position so it is needs to be there and can not be removed if bad just replaced. Could the shaft of the solenoid sticking and lube make a difference. Think I might try some WD40 on it and see if it ever does it again. If that is your only problem with the truck for awhile you should feel lucky.

Nope, sorry James. These are the opposite. I've removed plenty of these failed solenoid/ actuators.

 

[Floridianson]

Nope, sorry James. These are the opposite. I've removed plenty of these failed solenoid/ actuators.

That would made more sense than having to have it to start the truck or keep it running.

 

[74M35A2]

These solenoids have 2 coils within them, hence the 3 wires. One is a very strong "pull" coil, which will have a lower resistance to initially and quickly "pull" the solenoid open. This circuit is activated during the "crank" sequence. This coil is only rated for temporary use, or it would overheat.

The second coil is the "hold" coil. It is rated for continuous duty, and holds the solenoid plunger back one it is retracted during crank. It will have a higher coil resistance, hence lower power.

If your truck won't shut off, it could be like stated in above posts. Plunger not extending, or rubbing something. Check the shut off cam lever to shaft connection also, that has been found to be a slight issue as well.

This solenoid can be removed and discarded, as the shut off cam is a spring loaded lever which slides against the solenoid plunger. You would then need to pull the shut off cable each time to stop the engine, but same effect. Fail-safe position then becomes engine run, not engine off.

Separate from the original post, I keep a few large zip ties on board to strap this solenoid open should it fail. Also, during extended cranking, this solenoid will fall to the stop position as battery voltage drops during cranking. You don't know this unless the hood is open and you actually see it happen, as cranking is still fine at this transition point.

 

[wbread99]

Thank you, everyone. I'll play with the fuel cut off solenoid and report in. FYI, the truck started and stopped normally several times after pushing the emerg stop cable back in. Didnt need to reset anything on the pump.