M923 starter would not disengage.

[C Big]

I loaned my M923 the local VFW yesterday for a MV show and tell. When it got time to go home I went to start the truck. The starter engaged and would not disengage. I pulled the engine kill which killed the engine but the starter continued to run with both the battery and starter switches in the “off” position. Fortunately I had a pair of pliers on me and I was able to start pulling off battery cables till it stopped. Things were starting to get pretty hot before it stopped. After the starter cooled off I reattached everything and it started just like it’s supposed to. No problems at all. I started it 5 - 6 times to see if it would do it again.

Is this a common event? I could not find a thread discussing it.
I was surprised that I had to take off 3 battery cables to get it to stop. (I thought it would have when I took the first one).

I was going to put in a keyed battery kill switch between the battery box and the dash for security reasons, but it would have been nice to cut the power.

 

[machinist75]

Maybe the solenoid is sticking.

 

[BigWill1985]

Maybe the solenoid is sticking.

That's my thought as well. Although I haven't seen it specifically on these trucks, I have seen this happen on the Detroit Diesel 6.5 liter turbo diesels in GM vehicles. The contacts inside of the solenoid slowly oxidize, and a layer of black crud covers the contact surfaces. So, it turns into a slippery slope after that. The contacts become hot due to reduced surface area, which can speed up the oxidation process. Eventually, the contact surface area is reduced enough that the heat is enough to weld the contacts together. That's when you have the issue you described.

As long as the starter, battery cables, and batteries are in good shape you can get by just replacing the starter solenoid. You will want to check the battery cables at every sharp bend, to make sure the insulation hasn't completely melted through or cracked.

Good job getting the cables pulled before things started on fire!

~Will Courtier~

 

[machinist75]

As long as these trucks sit the solenoid is probably covered in corrosion. I've never done it but maybe the can be cleaned or a starter repair shop can remedy the issue.

 

[juanprado]

Solenoid sticking is very possible. Solenoid is easy to change and starter does not need to be removed. That is what I would start with if it was my problem.

 

[trooper632]

take out two batteries and run it only with two, faster to get the cables off, don't need four batteries in TX anyway.

 

[rchalmers3]

Happened to me also. Mine was after a low battery condition that I assume made for contact welding versus making a solid contact.

It won't cost you but some time and effort to pull down the starter and file the solenoid contacts. They are big and can take a cleaning without throwing them out.

Rick

 

[C Big]

I will take off the Solenoid tomorrow (July 5th) and let you know what I found

 

[BigWill1985]

Any update?

~Will Courtier~

 

[Retiredwarhorses]

As you stated, put a keyed cutoff switch on the ground side of the batteries...I do this on all my MV's I keep....this way when I Work on them I just turn the battery discconnect and I'm good....plus It's great for long term storage and security.

 

[C Big]

put a keyed cutoff switch on the ground side of the batteries

why put it on the ground side and not the positive side? My concern would be that if the truck had a short you could not stop the problem with the kill switch on the ground side. can you explain.

 

[C Big]

Update

Well I took it apart and found no evidence of “wielding” I have started it 20-30 times since and have had no more problems. My next step is to put the disconnect switch in.

Any other ideas what may have happened?