M1010 Won't shut off

[Pops506th]

Howdy. I'm fairly new to the site and really appreciate the info here.

I'm new to the CUCV world, but not new to the MV world.

I just picked up a M1010 ambulance and am having some issues with it. I've got some charging system issues, but that's not what I'm trying to fix right now.

Just last night the truck would not shut down when I turned the key off. It would shut down if I pulled the neg batt cable. When I turn the key off, the parking brake indicator light remains lit. I figured it must be a bad ignition switch, so I changed it out. The problem still remains. If I shut the switch off now and leave it for a few minutes, everything shuts down like it should.

As far as I can tell, the electrical system has not been tampered with. It still has the stock DUVAC as well.

Any ideas?

 

[Warthog]

This is coved in the technical manual TM 9-2320-289-20.

Check the small black ground wire above the emergecy brake.


The truck will not shutdown if the headlights are on and the wire isn't making good contact.

Visit the CUCV Wiki page and the CUCV FAQ.

You can get the manuals from www.jatonkasm35s.com

 

[Pops506th]

Headlights are not on and ground wire (the one attached at the bus bar ground) is in good shape.

 

[XanRa]

The truck will not shutdown if the headlights are on and the wire isn't making good contact.

who ever designed the electrical system for the cucv should be shot.... or at least publicly humiliated lol

 

[CPAPPY]

What happens if you pull you light out /on. Will it shut off when you push them back in . I had a problem like that and it was a ground .

 

[Pops506th]

I've worked the headlight switch back and forth. Nothing changes.

When I shut the switch off, the engine will continue to run for a minute or so then shut down. It is like a relay is sticking, but I can't find one in the schematics that would cause a problem like this

 

[Warthog]

The fuel shutoff is on top of the injector pump. The larger pink wire plugs into it.

Sometimes the coil will stick.

 

[Pops506th]

The fuel shutoff is on top of the injector pump. The larger pink wire plugs into it.

Sometimes the coil will stick.

Would that cause the parking brake light to stay on as well?

 

[timothy676]

I had the same issue with my M1009 and it was the glow plug control card, the card was melted, pulled the card and replaced withg a bypass switch and the issue went away.

 

[Pops506th]

I had the same issue with my M1009 and it was the glow plug control card, the card was melted, pulled the card and replaced withg a bypass switch and the issue went away.

I'll check that out. Thanks.

 

[Pops506th]

Ok, I pulled the glow plug control card and it looks in good shape. It still cycles the glow plugs on start up like it should. I started the truck normally, pulled the card and it still continues to run for about a minute before shutting off after I turn the key off. The parking brake warning light is also lit (I do have the parking brake set) during this time.

This leads me to believe that somewhere, something is keeping the power to the ignition circuts for this time.

 

[chevymike]

Hi and welcome to the M1010 club!

Interesting problem. I am wondering if something is bleeding power back into the system via the DUVAC or TWINPUT. There could be a capacitor that is staying energized until it bleeds off its charge and then shuts down the power.

There is a wire that comes from the ignition to the TWINPUT (small blue vertical item next to the DUVAC). I don't have my TM in front of me but there's one (I think second from the bottom connector) that should cycle when you turn on and off the ignition switch. Check with a meter that that circuit is actually turning on/off with the key (without starting the engine). If it's working correctly, start the engine and have you meter on that circuit and see what happens when you turn off the key. If it still have power, it is likely backfeeding the ignition and likely is defective.

Just an idea to test based on my experience of removing the DUVAC and going to a 12 charge/start system.

 

[Pops506th]

Thanks Chevymike. I'll check that when I get home this weekend.

 

[Pops506th]

It appears that the Twinput was the culprit. I replaced it with one from a parts truck and the truck shuts down like it should.

On another subject, what should the voltages be at each of the terminals on the Twinput and the Duvac while the truck is idling? I'm getting various readings that don't seem to make any sense.

 

[chevymike]

Great, glad you got it fixed. Sorry I can't give you the info you are asking for though.