m931a2 emergency shut off issue

[Desertshark]

Well plain and simple my emergency shut off fried... What i did was start truck to let warm up like i always do. Went inside to do some things . Came back out and truck was not running anymore so a little puzzled. I climbed into cab to see what was up, could smell burned wire.. My mind started to race so i shut everything down in correct order. Popped hood and smell was stronger. Looked and could see right away what caused smell. Some how it fried... Before i order a new one anyone have any advice on them? also is this a common issue or my luck? lastly after i get new one installed should i look for anything else that may have gone with it? Anny help would be greatly appreciate
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[74M35A2]

That is just the regular shut down solenoid. They are marginal to begin with.

 

[Desertshark]

So I should not freak out too much that it tried to melt down while it was suppose to be warming up? Just swap in new one and all should be good?

 

[74M35A2]

Mostly no. It can overheat if the pull coil stays engaged, but that is energized from the starter motor. If you want you can make sure there is 24v on 1 or both wires when compared to the (third) ground wire, and then only +24v on one wire when running.

They are kind of a PITA. Some people even run without them. I'm contemplating doing the same. They disengage when extended cranking, and can prevent the engine from starting, requiring to be zip tied back.

 

[Desertshark]

Sounds like ditching it may not be a bad idea. I figure just unplug it and remove unplug and good to go?

 

[wreckerman893]

I have known these trucks since 1991 and those solenoids have always been problematic.

If you stood in the Motor Pool on a quiet night you could hear them disengaging on all the trucks with low batteries.

The wrecker I was baby sitting had the same issue as yours. I yanked it out and manually shut it off with the emergency shut down. You just have to reset it every time or you'll wear the batteries down trying to fire it off.

 

[Desertshark]

Well I ordered another one earlier today. Should be here in a day or two so I guess in the mean time the sandshark gets the weekend off.

 

[WillWagner]

Biggest cause for that issue is high resistance grounds. When you get your new one, check the voltages and grounds through the harness. If the ground circuit is high...greater than 5 ohms back to the batteries, ground it directly to the engine. You need to check grounds, engine to chassis, chassis to cab, engine, chassis, cab to bat neg

 

[74M35A2]

.

 

[74M35A2]

Engine ground connection junction of 8.3L is front right lower corner of block, below alternator. Remove all, wire brush, reinstall.

 

[162tcat]

I have known these trucks since 1991 and those solenoids have always been problematic.

If you stood in the Motor Pool on a quiet night you could hear them disengaging on all the trucks with low batteries.

The wrecker I was baby sitting had the same issue as yours. I yanked it out and manually shut it off with the emergency shut down. You just have to reset it every time or you'll wear the batteries down trying to fire it off.

Why would you hear them disengaging? The resting position is disengaged.

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[Desertshark]

So got new one mounted and in... new issue. With power on now it won't energize properly. I have to get out and push in stub . Then wI'll start. Should I look at the grounds and make sure are good ? Could that be why it don't pull in automatically like use to?

 

[doghead]

Use a DMM and test your wires for proper voltage and ground. This was posted in post #8.

 

[Desertshark]

Ok will do.

 

[74M35A2]

This is proper behavior. It will not pull up with just ignition on. The hold coil is active with ignition on, but the pull coil is fed from the starter motor, so the solenoid does not pull up until you are cranking. Once pulled up, the hold coil will keep it there, which is why it stays up once you push it, you are acting as the pull coil, normally power fed from the starter motor.

If extended cranking, the pull coil gets hot, resistance increases, and the plunger will extend, resulting an engine no start. This is a hard one because you really can't see it from the cab even with the hood open, and the starter does not slow down when this is happening, so there is really no reason to think it is occurring, but it does. I carry a large zip tie to fasten the plunger up if I even need to do extended cranking. I have run out of fuel more than once, for various reasons, so.......

 

[WillWagner]

Pretty much as stated above. The pull in part of the solenoid circuit will not pull in until the starter is engaged. When the button is released, the hold in voltage takes over. You should still check all of the B+ and grounds.View attachment FSOV Specs004.pdfView attachment FSOV Specs003.pdf

Grounds need to be well below .5 ohms. Cummins says 10 ohms is good, but it isn't

 

[Csm Davis]

I just pull mine and use the emergency shutdown cable to shutdown, it works every time and pulls the same arm the solenoid pushes.

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