M931A1 NEW OWNER

[zeik]

Hi guys. Just purchased my first m931a1. Im fact my first military truck. Im in Atlantic Canada. Crossing the border to bring it back was not trouble free. About a 150 km drive with a thirty plus year old truck I've never seen or driven was little nerve wracking. HAAAA. Start up wasn't bad little ether fired right up. Noticed right away an air leak. Parking brake wouldn't release. I was smart enough to bring two crates of tools, repair solids and liquids and tape, ties. Managed to crudly fix line. Got brake off. Thank God for Mike at the package depot who received my truck from shipping in calais Maine. He let us put truck in his shop to thaw and drain the lines and tanks were all frozen. MIKE you are the best. Finally on the road, through the border check points. The truck was running good. The parking brake light and buzzer would not shut off that drove us nuts. Any ideas? We played musical doors cause the handles were stuck at one point or another. I don't think oil pressure gauge is working the needle is bent. The speedometer or odometer isn't working so what I thought was a 1700 mile truck I was buying i now have no idea. I am aware that I will need to change all fluids. Check all air and fuel lines, adjust brakes, belts and hoses on a truck this age that sat a lot. Any ideas on my current problems and ANY OTHER ADVISE on things I should be aware of on these trucks I would apreciate. We finally did make it home without breaking down. Mission accomplished. I got big plans for this truck which I will discuss and post about another time with my questions after I have scoured this site for answers first. I joined this group in hopes of having access to the knowledge you guys have earned the hard way. That is usually how I learn too. Haaaa. I look forward to digitally speaking with some of you guys. Thanks in advance. Here's a pick of the truck 1990 model.

 

[silverstate55]

Nice hardtop! Welcome aboard!

You’ll probably need to service or replace the air dryer. Also check the flexible fuel lines from each tank for cracking; if they show any signs of cracking, replace them all…that will resolve any issues with air seeping in to fuel system & causing you to lose your prime.

Since your truck has the 14.00 Super Singles, these are known to bounce & vibrate at highway speeds, and this causes cracks in your fuel tank pickup lines at/near the fuel tanks (And cause loss of fuel prime). I even had a pickup tube fall out inside a fuel tank; after fishing it out of the tank I had it brazed to prevent it from happening again.

The grease fittings for the short jack shaft between the transmission & transfer case are a real pain to get greased.

Others will be along shortly to offer better advice. Congratulations on your purchase, and interested to hear about the border crossing story.

 

[zeik]

Nice hardtop! Welcome aboard!

You’ll probably need to service or replace the air dryer. Also check the flexible fuel lines from each tank for cracking; if they show any signs of cracking, replace them all…that will resolve any issues with air seeping in to fuel system & causing you to lose your prime.

Since your truck has the 14.00 Super Singles, these are known to bounce & vibrate at highway speeds, and this causes cracks in your fuel tank pickup lines at/near the fuel tanks (And cause loss of fuel prime). I even had a pickup tube fall out inside a fuel tank; after fishing it out of the tank I had it brazed to prevent it from happening again.

The grease fittings for the short jack shaft between the transmission & transfer case are a real pain to get greased.

Others will be along shortly to offer better advice. Congratulations on your purchase, and interested to hear about the border crossing story.

Thanks for your two cents I'll definitly take it. I haven't had time to really move the truck since I got it home. It's going in to get fifth wheel taken off, new hitch plate for bigger pintle and 2.5 inch receiver , tail light relocation and a complete service and check over before I start to use it for towing my equipment around. My plan is to check all the items you mentioned as well. Im sure I'll have a million questions. After this construction season the plan is to install a dump box on back. Don't know if scissor or front mount hoist yet. Possibly a plow if I get to it in time or on the list for the following winter.
Thanks again

 

[silverstate55]

The tech manuals for your truck are available for download, so I would encourage you to do so if you haven’t already. The A1s with the NHC-250 Cummins has a lot more low-end torque than the A2s so it will be perfect for towing for you. There is a LOT of great info on this site about these trucks.

As has been pointed out in other threads like these on M939-series trucks, full fluid & filter changeouts are your first priority. And, make sure you grease everything thoroughly (found in the LO lube order).

The lack of other comments here is pretty much good testimony to how reliable they are.

 

[US6x4]

Don't back up with the transfer case in low (no bueno for the t-case) and when you shut down the engine, shut off the engine switch first then after the engine is done rotating shut off the battery switch. This prevents frying the voltage regulator in the alternator.

 

[zeik]

Hey guys. Thanks again for your input. So just to be clear I am not to reverse with the transfer case in Low only?. It's ok to do in 6 high?
I just moved the truck from my yard to my very awesome and loyal shop where I'm arguably their number one customer. I always bring them a challenge which is running joke there. In this crazy expensive world of buying new equipment to make money with as a Gen X guy I breath fresh life into their shop by believing I can buy cheap, build, and fix good quality equipment to do my work. I don't give a shit how new or shiny it is. If it does the job, it does the job. I am all too aware I just need more items so I'm not stranded while working on one or two. Fine with me. It's still overall cheaper in long run versus payments AND fixing/maintenance.

I see one of you mentioned down loadable manuals. You got a link to those? Is that the Texas site i see on line? Also I'm a bit old school and wouldn't mind having hard copy books to actually read in my hand. Are they available as well?.
Again. I have made a list of every item you guys mentioned and taped it to the windshield for my shop to go by. Anything else that pops into your heads please share. I AM taking notes.
I love doing some of my own work when I have time. That's the biggest issue. I don't have a lot of time to tinker. I don't have on staff mechanic or shop big enough for that truck. YET.
Thanks again.

 

[ericp351]

Yes- trouble with REVERSE and LOW only! Look for any dash tag. This site- topics has those manuals "down-loads", above. Ask venders for paper copies. Fun tip- check your fuel cut (solenoid by rack) if crank-no start BEFORE batts die. Tie "open"- plunger retract, if troubles underway. Think most people go to 2 #31 batts as reqd. #1 is fluid changes, filter service and lots of grease as advised above.

 

[zeik]

Yes- trouble with REVERSE and LOW only! Look for any dash tag. This site- topics has those manuals "down-loads", above. Ask venders for paper copies. Fun tip- check your fuel cut (solenoid by rack) if crank-no start BEFORE batts die. Tie "open"- plunger retract, if troubles underway. Think most people go to 2 #31 batts as reqd. #1 is fluid changes, filter service and lots of grease as advised above.

Awesome thank you. Making notes. The truck has started fine every time up until yesterday. I had ZERO power to anything. Tried boosting and charging one at time only two batteries under the seat. Its actually the first time I've seen 2 batteries completely gone. They looked fairly new but wouldn't charge or carry a boost. I put two brand new 31 batteries in and it fired right up. All the cables are in the box for 4 batteries I'm wondering if I should have 4. But I want to make sure that nothing is killing the other two before I do that. Any thoughts?

 

[zeik]

Quick other question. I tried downloading the manuals from this site it won't even let me open them. Do I need to be a higher level member for that? Thanks.

 

[Mullaney]

Quick other question. I tried downloading the manuals from this site it won't even let me open them. Do I need to be a higher level member for that? Thanks.

.
No. No restriction on downloading - even by non-members. It is pretty cheap to be a member ($15 for a year) and unless I missed it, you already are. The files in the TM section are mostly PDF's. You need an Acrobat Reader (free download from Adobe) to view those files.

 

[silverstate55]

Awesome thank you. Making notes. The truck has started fine every time up until yesterday. I had ZERO power to anything. Tried boosting and charging one at time only two batteries under the seat. Its actually the first time I've seen 2 batteries completely gone. They looked fairly new but wouldn't charge or carry a boost. I put two brand new 31 batteries in and it fired right up. All the cables are in the box for 4 batteries I'm wondering if I should have 4. But I want to make sure that nothing is killing the other two before I do that. Any thoughts?

The 4 batteries are for extreme cold weather starting that may require extended cranking times….the military loves redundancy. 2 Group 31 batteries are just fine, especially if you install a block heater.

As for battery life, I got 10 years out of the stock military batteries before they did the same thing you experienced. It happens. I don’t recall too many parasitic draws from these trucks, but who knows what previous owners have modified/installed.