M915A4

[Charlie175]

Our Town has a M915A4 (since 2014 or so) from Gov't surplus. Used very little with 16,000 or so miles on it. Been sitting 2 years and they are getting ready to put it up for Public bid. I know little about semi's but am trying to help them get it running. Batteries were dead so tried to slave jump it from a Hummer but that didn't do much, only gave it enough juice to get the gauges up but not turn it over. Pulled the batteries out to charge and they are in the 8 volt range. Hoping they will recover enough to hold a charge. The 4 Batteries are from 2011.

Master Power on, and then turn Key to on, and push to start is all I see to do. Allison display came on and went to N.

With the slave hooked up the Voltmeter was in the 16 volt range (12 volt gauge) but when the key is turned on the volts drop to about 10 or so. I assume the truck uses 24 volts but converts it to 12 at the dash?

 

[ODAddict]

The batteries are very likely unusable from both age and exposure to heat and cold. It takes a lot of power to start that engine. From what you've said, and from my experience with big trucks, the easy (though a bit expensive) way is to buy a new set of batteries. It's difficult to get enough juice from the slave cable or basic jumper cables. Hope that helps.

 

[Charlie175]

I thought about taking the batteries out of my Deuces and putting them in to get it started however my batteries are larger than what came out of the 915 so I doubt the cables will align. If I can't fit the 4 of them in there I doubt 2 of them will have enough cranking to get the job done.

 

[Charlie175]

Looked it up and the batteries are $699 each!

 

[ODAddict]

We used to own old International 2554s with Detroit Diesel engines. When the batteries went down, we tried to limp along with using jumper cables, etc to start the engine just to get through the day. One time we tried hooking up two portable jump boxes along with a jumper cable from a running truck. It was barely enough to turn over that engine, and we gave up trying to nurse depleted batteries. We bit the bullet for a new set and were glad we did. It's no fun fighting equipment.

It's very likely the newer M915A4 engine with only 16000 miles has much higher compression than that 30 year old Intl with hundreds of thousands of miles.

$700 for a single battery is a lot of money. If you could find batteries that fit for $300-$400 each, you'd be doing well.

Heavy trucks have their own set of issues, especially when they sit for 2 years. For example, unless you start the engine, you won't know if the compressor builds air or, if it does, what air line leaks you may have.

The Allison transmission is a generally a reliable unit, but will it pull a loaded trailer and shift properly? Tires are very expensive. Make sure you check for dry rot and cracking, etc. Fuel is another issue; diesel has a tendency to grow things like algae when it's been sitting. Two years is probably OK, but I'd be wary of possible clogged fuel filters, etc.

Bottom line: No one really knows much about this truck until it starts.

I found and old thread on SS which may be of interest: https://www.steelsoldiers.com/threads/m915a4.85573/

 

[Charlie175]

Thanks for the replies. I had read that thread yesterday for info. Tires were replaced a few years back but I haven't looked at the date code.
They also have a Military trailer, forgot the number but it's a Fontaine from 2006. Good shape but they have no title for it.

 

[NDT]

Put two group 31s in it. You will burn up ECMs and who knows what trying to slave start it.

 

[kubotaman]

Put two group 31s in it. You will burn up ECMs and who knows what trying to slave start it.

Ditto. 2 Group 31s or the batteries from your deuce will be plenty in warm weather.

 

[Charlie175]

OK, the cabling has me a bid confused. Row nearest truck frame (Inner) has red cable covering the positives on 2 battery. In the middle another red cable linking 4 batteries positive (Outer battery) to negative(inner row battery) to positive(Outer battery) to negative(Inner row battery). Last outside row is black linking the 2 negatives.
If I use 2 batteries which ones do I hook up to?

 

[fuzzytoaster]

I have 5 of these M915A4R2s and they do require a lot of juice to fire up. The power system is similar to the FMTV in the sense that the 24v pulls so much voltage the the 12V drops out when trying to slave start. Group 31 or 65 batteries will do the trick if the outside temp is somewhat warm.

The red cable towards the frame is your 24v +
The cable with alternating +/- (between the batteries) is your 12v+
The black cable closest to you is the 24v -

In this case put both batteries to the left of the battery box (closest to the front tire). Use the alternating +/- cable to connect between them.

Also, where is it going to be listed?

 

[Charlie175]

Thanks,
Truck listing is due out next week. I will pass it along when it does

 

[Charlie175]

Tried 2 Group 31's, got 12 volt on dash gauge, buzzer sounded strong but only clicks on starter.
Some pics I took

 

[NDT]

She’s a beauty. Does the volt gauge go to zero when you push the starter? Fuzzy what crank inhibits do these have? I think none other than the Allison controller being in neutral. Check the starter for bad connections.

 

[Charlie175]

Volts stay up. Yes I do need to check all the connections and see what volts I have at the starter.

 

[NDT]

Recall that the engine in these started life in 44 year old M915s, so it’s possible the starter is ancient too.

 

[fuzzytoaster]

She’s a beauty. Does the volt gauge go to zero when you push the starter? Fuzzy what crank inhibits do these have? I think none other than the Allison controller being in neutral. Check the starter for bad connections.

There is an actual fuse panel under the main dash so check fuses there. Some are non-resetable. The TCM not being happy can be an issue. Otherwise poor continuity to starter. Only the starter, black out lights, and trailer 24v pigtail are 24v. All other systems are 12v. I've found these trucks to be notorious for weird harness issues around the steering column and simply shaking things make them better.

Wait.. I want to buy it. Why am I helping? (it's the right thing to do.)

 

[Charlie175]

Thanks for the tips

 

[Charlie175]

To update everyone the listing is still not up. Should go up next week but I will pass it on

 

[Charlie175]

it's Alive! Had to put a starter in it but then it cranked right over and fired up. Now we can finalize the listing.

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