WSUCougar's M925A1 Acquisition and Build Thread

ABS Troubleshooting...talk about testing patience

After the battery issue was solved, I turned my attention to that blasted ABS Light on the dash. As mentioned previously, the light is always on. This indicates a faulty ABS system and the truck should not be driven over 40 MPH. To me, 40 MPH is still too fast with how well these brakes work. I did have some lock up issues during my recovery trip home and, quite truthfully, it scared the crud out of me a couple times. Nothing like having the rear end trying to slide to the side.
Anyways, before tackling this issue I printed off a copy of "Field Maintenance Troubleshooting ABS Without Diagnostic Tools" from TM 9-2320-272-23-2 pages 0156-1 to 0156-15. It has a step by step process on how to check your entire ABS system one component at a time. The process is actually quite easy, just time consuming. I love stuff like this anyways.
So a summary of what you're suppose to do in order:
1) Check both wheel speed sensor leads in the rear axle
2) Check to make sure both front and rear ABS Solenoid Valve Connections are OK (3 prong plug that screws in)
3) Check the ABS wiring harness 28 pin connector.
4) Check the ABS wiring harness
5) Check the ABS Power Supply Connection (circuit #10)
6) Check the ABS Ground Wire
7) Check the under the dash ABS Harness Connections
Check Circuite #54 from the Starter switch (Is the 3 AMP fuse OK?)
9) Check the battery voltage (between 21-24 VDC?)
10) Check the ABS Volatage Supply w/multimeter
11) Check the ABS Ground Wire w/multimeter
12) Check the under the dash ABS wiring harness wire individually w/multimeter
13) Check 15 AMP fuse and wires w/multimeter

So heres the deal with my truck. When you go to start up, the ABS system does try to do the self-check. However, it only does half and the ABS Light stays on. Now when I say half I mean you only get 1/2 of the audible clicks from the rear of the truck. During the normal self-check, after flipping both switch (but not engaging the starter) you hear two series of 3 clicks followed by the ABS light turning off. In my case, I only got one set of 3 clicks followed by a sustained ABS Light. So I went to the task of checking everything mentioned above not once but twice to no avail. I traced every single wire checking for abrasions, nicks, cuts, burrs etc etc. Nothing!! I checked every connections 6-7 times each to no avail. I pulled out the dash wires to see if they were mismatched...nothing. I wacked the ECU with a rubber mallet...nothing. I found that whoever put this unit together or whoever replaced the 3 AMP fuse put a 30 AMP fuse in instead!!!! I thought for sure the ECU was fried. I went down to NAPA and secured some 3 AMP fuses and came home to try it out. I was expecting the fuse to blow as many have had their 3 AMP fuses blow when the ECU was fried. However, mine did not blow. Maybe there was hope for my ECU. Then I just sat there and stared off into space. Then it hit me. What was the source of the "clicks" during the self-check? What did the "clicks" represent and why? I recruited my son for this task. As I laid down in the wet gravel, he sat in the cab toggling the off/on switches. I found out the "clicks" were coming from the ABS Solenoid Valve units. The reason for the two sets of clicks is because there are two ABS Solenoid valves (front and rear). I found the Rear Solenoid Valve unit was making the clicks but the front unit was not. The front unit is also where the ABS ECU is. Hmmm, I thought if my ECU was fried then how would the ABS Solenoid know to do the self-check.....OK, now we're onto to something here. I ran into my garage and searched for a spare ECU/ABS Solenoid Valve unit I bought off ebay for $35 last year. I disassembled the ECU portion off the bracket so I was just left with the Solenoid valve. I crawled under the truck and disconnected the front solenoid valve wire from the old unit and connected it to my spare. I kept the original ECU in the truck hooked up. I jumped into the cab, said a prayer that this would work. I switched on both switches......I hear the first set of clicks....pause.............then there it was, the 2nd set of clicks......I look down to see my ABS light...........shut off. It worked!!!!!! So my ECU was good after all. Just had a bad ABS Solenoid Valve unit!!! All this took 8 hours of work!!! But hey if I don't roll over the truck and die then 8 hours was worth it

Projects Completed:
ABS System Fixed and Fully Operational!!

Pics:
1- Speed sensor leads. Check the two prong connections. Located right on top of the rear axle.
2- Rear ABS Solenoid Valve (click click click)
3- Speed sensor going into the hub of the rear axle.
4- ECU 28 pin wiring harness and plug
5- ABS power source (Circuit #10)
6- 30 AMP fuse in the 3 AMP's place.....seriously?!?!?!?!?
7- My spare unit I robbed parts off of
8- The old ECU mounted just above the middle axle. If I were any fatter I wouldn't be able to fit between the air dryer and axle.
9- The two connections going into the front ABS Solenoid Valve/ECU assy
10- Having the original ECU hooked up but using my spare ABS Solenoid to rule out/rule in a faulty solenoid unit.

Nice truck, good write up on the recovery. That was great the batteries was good and the cable was the problem.

Good job ! Make sure you shut down the truck correctly or you could fry the ecu.

MIKE!


THANK U SO MUCH for the detailed Pictorial.
That is ABSOLUTE GOLD ... Everything about it could,
and I am sure will, save possibly myself and others in the future...

Hardtop Project

Haven't had a whole lot of time to work on the 925. Yesterday and today were devoted to the hardtop. The interior of the truck isn't exactly up to my standards. As previous discussed, I was after a Red River Depot truck. The reason being is nothing looks like a newly CARC'd cab with a new hardtop, seat cushions, and the nice green floor mat. So in order to get the truck up to standard, I decided the start from the top and work my way down.
The hardtop was used as either as a podium or a park bench. Not really sure which, but definitely used for somthing as parts of the hardtop were caved in 3-4 inches. Also, the foam insulation on the hardtop is pretty bad. It is almost disintegrating and full of holes where moss is setting up residence. Plus it's to the point where it is saturated with old stale water, giving the truck a nice odor.
Yesterday, I devoted my time in getting the hardtop low spots out. I originally planned on pulling the hardtop and working on it while on the ground. However I decided to not to. I felt it would be much easier to apply upward force with a jack rather than smacking it with a rubber mallet. I figured the hardtop is already held in place so no worries on securing it to something. I just found a piece of 4x6 and a bottle jack. To gauge my progress, I used a piece of fiberglass to eyeball the level of the hardtop. One thing, you have to be careful about yanking the bolts that marry the two halves together. The metal on these hardtops aren't exactly thick. I also found the installed didn't use one washer in the mounting bolts Once everything looked good, I took the two parts apart to work on the foam insulation. This part was pretty easy as whoever put this hardtop on, only used 6 lousy bolts to hold it all together. No wonder she leaked like crazy and rust is everywhere. Man, this proved to be a challenge. I didn't have Soldier B around to help. I gently lowered the hardtop to the deck without losing my grip and muscled her to the backyard. No room in my garage as green parts have taken up residence and are scattered all over the floor. Not sure how that happened
I stripped everything down, scraped all the rust out, sanded the stubborn rust spots, and threw a coat of Rusty Metal Primer. Luckily, the rust didn't eat all the way through the sheet metal.
Today, I finished taking the foam insulation out of the hardtop. I made sure not to tear it up too much as this was going to serve as my pattern to make it's replacement. I ended up using two USGI foam sleeping mats for the roof portion of the hardtop. I anticipate it'll take another two more sleeping mats to do the back of the cab. I recently got the foam insulation off ebay for $3.99/pad. I also painted the peg board material with a fresh batch of Home Depot's Behr Paint. I took a brand new 383 Green part down to Home Depot last night and they matched it exactly! I bought two gallons as this will be what I'll use to paint the cab.
Now if lowering the hardtop off the cab wasn't hard enough, I was now tasked with raising the hardtop into position. No Soldier B again, just me. Don't ask me how I did it, but I manage to lift that thing into the cab. Once I got her into the cab I just lifted it into position. Before bolting everything down, I wanted to seal the mating surfaces really well and take care of any future rust issues. My solution? GAA!!!! I put about 1/16" of GAA on the windshield/hardtop mating point. I also did the same thing on the two hardtop mating point. I put liberal amount of GAA on both sides of the gasket. Once everything was lubed up I put in 4 long bolts to S-T-R-E-T-C-H the old gasket into place. From experience, I know these gaskets like to shrink. Rather than start bolting from one end of the hardtop to the next, I just place 4 bolts into place to pre-stretch the gasket to make thing easier. Once I had stretching bolts into place, I just started putting my Grade 8 1/4" fine thread bolts into place. I placed them all in loosely to make sure everything was lined up before tightening them down. Also paid particular close attention to the gasket to make sure she was uniform along the edges. These gaskets like to squeeze out in different places. Once everything was tightened I called it a day . Next project will be fitting the foam insulation to the back of the cab.

Projects Completed:
-Drained Transfer Case
-Removed Hardtop Roof (treated rust/primed/replaced foam insulation)
-Mounted the Exhaust Stack Rain Cap

Pics (stinkin' out of order...grrr) :
1- Newly insulated and partially assembled/painted hardtop
2- Before shot with the nasty foam insulation stripped out as well as the metal hardware
3- GAA on the mating surfaces
4- Back of cab with foam removed showing the nice stucco rust arrangement
5- Rust long the hardtop
6- After shot once jacks were used to push the low spots back into place
7- Jack
8- Jack
9- Low spots in the roof
10- Before shot of the roof low spots

That was an interesting use of GAA. Hope it works out. When I rebuilt the M54 hardtop this last fall, i went with a bead of silicone sealer on the tops of both back gaskets, nothing except a good cleaning on the front top to windshield gasket. I thought if the top of the back gaskets were taken care of, the bottom would work out on its own. i even patched a few spots that were inherant leakers due to design. Then took a 3/8 strip of adhesive weatherstrip and went around the inside of the tip out windshield frame. That really knocked down the breezes. My bolts and screws for the top were not salvageable, so were replaced with stainless. While the top was off, the mechanism for laying down the windshield was worked over as well. I believe that the top had not been off and the windshield not layed down since its 1985 rebuild. The top sports a 1984 date.

Thanks Peter, I was going to put some polyurethane roof/flashing sealant on the joint. Then I thought about the water that had infiltrated and laid stagnant between the hardtop gasket and surface. There was some good rust in there, so much so I had to use a flathead screwdriver to scrap the rusty metal out of the gasket. I figure the GAA would add another element of protection for the metal surface. Once the weather improves, I am going to run a bead of the polyurethane on the outside of the hardtop joint to really seal her up. The great thing about the sealant is it's flexible and paintable.
Here are some pics showing the state of the "old" foam insulation and what I found underneath.

Why did these truck tops get the rough treatment? You have done a great job on your top. I need to uncave mine but was thinking about the best way to go about it.

Cab Plans

Ok so here's the plan for the truck. Just kind of thinking out loud and writing things down for future. At least I won't the information if it's typed here, right?
CAB
-Replace windshield wiper motor air switch with new ones (ebay $18.50 each)
-Add VIC-1 System (Already have)
-Add four M4 mounts (door mount and dash mounted)
-Add rearview mirror ($10 via Spruce Mountain Surplus)
-Add newer green insulated floormat (thanks beerslayer)
-Recover passenger seat (back and bottom cushion)-have material
-Add Route Clearance Light Switch Panel using all military rotary switches
-Add Back Up Light Switch using rotary switch
-Replace Heater Vent hose (been kicked one too many times)
-Add Red Interior Dome Light
-Add Combat Locks (already have)
-Add Fire Extinguisher Mount (Military)-truck didn't come with any
-Add 12v socket for powering SureFire Hellfighter Weapon Light
-Add ABC-M11 just for looks

-Replace all the dataplates
-May tint the windows but that's up in the air right now.
Once all the holes are made I will repaint the entire interior with the Special Formula Home Depot Behr 383 Green CARC substitute

UNDER THE HOOD
-Replace all hoses and belts
-Add Block Heater
-Add Coolant Filter
-Add Circuit Breakers for new wiring
-Replace all under the hood insulation-starting to disintegrate

EXTERIOR
-Add Route Clearance Lights-several
-Add IR Lights up front
-Add Armor Back Up Lights
-Add Pioneer Tool Rack
-Add Two Solargizers to the roof location
-Add Bumper Steps
-Add Antenna Mounts bedside and passenger fender
-Add Camo Netting Tray
-Add MTVR ladder to tailgate assy
-Add Towbar/Safety Chain storage area to the rear of truck
-Add Storage area up front behind the bumper
-Add Gerry Can mounts to mudflaps
-Add add'l Gerry Can mount to existing area on toolbox
-Add VIC-1 Station in cargo bed area w/LS-454 Loudspeaker
-Add Lightweight Weapon Station???? undecided which truck will get it.

Thanks for the great writeup. Whats the difference between the 925 and the A1 besides the single tires?

Nice. I really need to do some more research on the M9xx trucks to I know what you are talking about! All I know is you are doing great work, and the trucks always look awesome. Well done, again.

1 Patriot-of-many said:

Thanks for the great writeup. Whats the difference between the 925 and the A1 besides the single tires?

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Thanks The only difference between the M925 and the M925A1 is just the 14.00x20 super single tires and all the associated parts. The spare tire carrier is wider to accomodate the wider tire, the cargo bed was moved rearward for the wider tire carrier, and the bumperettes on the rear are deeper due to the bed being farther back. The spare tire davit is also beefier to accomodate the extra weight. Other than that, everything else is exactly the same.

Danger Ranger said:

Nice. I really need to do some more research on the M9xx trucks to I know what you are talking about! All I know is you are doing great work, and the trucks always look awesome. Well done, again.

Click to expand...

Thank you. I've found the best way to learn about these trucks is to get one. Upto this point, this write up hasn't been too exciting. Just been working on getting the platform upto standards before the real fun begins...hahaha. To me, this is why I buy these trucks. Guys wonder why I have so many truck because you can only drive one at a time. Funny thing is I don't buy them to necessarily drive them. The recovery and the build process is what it's all about to me. More problems/issues the better.

You're a project junky!!! Go see a banker, you'll need it before you hit rock bottom! I am too though. Mine is the Jeep.

Mike, you made me so tired reading about the projects that I have to go take a nap. If you need an exterior mirror, I may be able to help out. Have an extra new one that is wired for defrost. I didn't see that on your list of to do items.

wsucougarx said:

Thanks The only difference between the M925 and the M925A1 is just the 14.00x20 super single tires and all the associated parts. The spare tire carrier is wider to accomodate the wider tire, the cargo bed was moved rearward for the wider tire carrier, and the bumperettes on the rear are deeper due to the bed being farther back. The spare tire davit is also beefier to accomodate the extra weight. Other than that, everything else is exactly the same.

Click to expand...

Thanks again! I might have one of these in my future. How do you like it driving around town? Did you have to plate it commercial? Lastly, why the heck does it need four batteries?

1 Patriot-of-many said:

Thanks again! I might have one of these in my future. How do you like it driving around town? Did you have to plate it commercial? Lastly, why the heck does it need four batteries?

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Drives outstanding. Seriously, these 5 tons drive easier than my wifes Escalade. Albeit, these trucks hardly have any creature comforts...just the way I like it. I insured this truck with State Farm Classical Vehicle insurance. So I'm limited to 2000 miles/ year. No problem with the fuel economy of these beasts. My rate is $22.67 for 6 months of coverage.
The cold blooded nature of the NHC 250 Cummins needs the four battery configuration during cold starts. However, you can probably get away with two batteries in warmer areas.

What a great read. Thank you for taking the time to do it.

Good looking truck. Really appreciate the detail in your write-ups.

Mike, haven't heard from you in awhile so I figured its been raining too much for you to turn the wheels of progress. I too enjoy the posts and look forward for more!

Al Jones
'84 M923