M929 Won’t Start

[tmuenster]

My M929A1 Dump Truck won’t start. I bought the truck from Memphis Equipment and they did a 12v conversion on the truck, which in hindsight might have been a mistake.

I got out my volt meter and checked the battery first. The battery is at 12.5v which might be a little low but the truck has been sitting awhile. I did try to jump the truck and no luck there starting.

Next, I moved on to the solenoid for the starter. If I am not mistaken, I think there should be 12v at all three terminals when the ignition key is turned. Is that correct? I had 12v at one terminal but there was 0.0v at the other terminals whether the key was turned or not. Please let me know if you think the solenoid is bad and should be replaced.

Thanks,
Tom

 

[Mullaney]

My M929A1 Dump Truck won’t start. I bought the truck from Memphis Equipment and they did a 12v conversion on the truck, which in hindsight might have been a mistake.

I got out my volt meter and checked the battery first. The battery is at 12.5v which might be a little low but the truck has been sitting awhile. I did try to jump the truck and no luck there starting.

Next, I moved on to the solenoid for the starter. If I am not mistaken, I think there should be 12v at all three terminals when the ignition key is turned. Is that correct? I had 12v at one terminal but there was 0.0v at the other terminals whether the key was turned or not. Please let me know if you think the solenoid is bad and should be replaced.

Thanks,
Tom

View attachment 928471

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Well... Yeah, if you had known that it was 12v vs 24v you might have acted differently.

The best part is that the solenoid is a cheap fix.
You might find a bad switch.
Is it a key type switch?
They cause a lot of problems..

 

[Valley Rock]

The center wire is your activation wire for the solenoid, it tells the solenoid to do its thing and send juice to the starter .

When you turn the key or starter switch all the way to the start position, that wire should be hot, activating the wire on the right .

 

[juanprado]

A a quick test is to jump the solenoid with a screwdriver to complete circuit

 

[fuzzytoaster]

You should contact Doug at Memphis Equipment since he was your POC for the truck and the modifications. We here are just shooting in the dark based on basic operations of the solenoid. Who knows what they did to convert it.. . If anything you can screw in the fuel shutoff solenoid and jump it directly at the starter. If that doesn't spin the engine (at the very least) then you have battery or battery connection issues.

 

[tmuenster]

Thanks for all the help and suggestions. I did call Memphis Equipment this morning. They advised to check the fuses for the ignition. They are the old style glass fuses, which do appear to be fine. However, they said to check with a test light as the fuse holders can sometimes not make good contact.

The truck has been frustrating. I thought it would be less of a maintenance headache having been through the reconditioning process at Memphis Equipment. In the end, all equipment especially military vehicles will need some maintenance I guess.

 

[Valley Rock]

My old Deuce only had one fuse that I know of and it's at the fuel pump .

My M931 doesn't have any fuses that I know of, however I've never really looked because it's never had a problem .

Did your truck originally come with fuses ? or is this something somebody added when they messed with the perfectly good 24 volt system ...

 

[tmuenster]

Did your truck originally come with fuses ? or is this something somebody added when they messed with the perfectly good 24 volt system ...

Unfortunately for me, I requested the truck be converted to 12v when I ordered it from Memphis Equipment. My rational was it would be easier to jump when necessary. Also, I was adding other 12v accessories such as AC; backup camera; and some phone charging ports. The AC is a must in my view as the summers in TN can be dangerously hot. In hindsight, I would not do the 12v conversion based on what I now know. Attached please find a photo of the fuse box. I’ve tested the circuits with a test light and they appear to be working correctly.

The good news is Memphis Equipment has agreed to pick up the truck and have their techs inspect the electrical system and axle seals, which also went out. They have been very helpful as I have tried to diagnose the problems over the phone and through email but it is just a bit beyond what I can fix at the moment. I am clearing some land to build a cabin and a shop so my tools are either in my truck or a shipping container. It makes things challenging to work on equipment in the field.

 

[tmuenster]

The center wire is your activation wire for the solenoid, it tells the solenoid to do its thing and send juice to the starter .

When you turn the key or starter switch all the way to the start position, that wire should be hot, activating the wire on the right .

I did try jumping the solenoid. I could get a “click” like it was trying to start but the engine would not turn over. The truck has been hard to start from day one. I do not have all the specs on the 12v conversion but I suspect these trucks start better with the higher 24v current. In the past, I would turn the truck’s key, there would be a ‘click’ then would take a few seconds before the engine would turn over. My other 24v military vehicles will nearly instantly turn over when the ignition is switched to the start position.

It’s been frustrating knowing that I did this to myself by ordering the 12v conversion.

 

[LCA078]

You may want to see if you can "de convert" back to 24v while it's back at Memphis. I know it sucks paying double for nothing but it might be better in the end.

Lastly, there a many, many 24v to 12v dc converters available on Amazon built for exactly what you're looking to do. Lots of folks use these 48/36/24v converters to power 12v accessories on their golf carts. May be a whole lot easier on your 'next' purchase.

btw- congrats on a M929 purchase! Hope it works out for you in the dirt!

 

[Valley Rock]

What he said

And as far as you lights go you can just use LED lights, they work from 6 to 36 volts, as for your turn signals they now make flashers that work with the low resistance LED lights, so that's no longer a challenge .

Modern-day phone chargers typically just have a USB outlet that the cord plugs into, you can hook them straight up to 24 volts and it takes care of that for you as well, they are what I use in my trucks .

Your air conditioning is going to require a good dose of 12 volt amperage, and I'd bet what you need is available to drop it down to 12 volts and carry that amperage .

The only thing in my entire truck that is 12 volt is one of the old school style push-in sockets like lighters used to use, that my cab fan plugs into so it can blow the heat around in the cab and make it more like a furnace .

I hope they put it back like it was for you so that you can enjoy your truck

 

[tmuenster]

The truck is back at my farm and seems to be staring much better. Memphis Equipment really stands behind their work. They re-worked the wiring harness to ensure everything was working properly. Apparently, the issue was between the solenoid and starter. I also added a water buffalo to the mix so it was not all bad.