Many M816 Questions

[BillTWD]

New to forum so if I placed this in the wrong spot please let me know. I'm most likely going to sound like an idiot because I know almost nothing about the truck I bought but I love it and want/need to learn. Short introduction - I bought a 1972 M816 wrecker sight unseen and had it delivered. It was advertised as a 1976 and the listing said that everything worked. None of that was true. It turned out to be a 1972 and has a lot of problems not to mention my total lack of knowledge of this type of vehicle. Perhaps the biggest "issue" is that the transmission won't go into 4th or 5th gear (has reverse and 1, 2, 3), I know a guy who says he can fix that so I'll skip that for now. The second biggest issue is that I can't get the RPMs up. The engine starts nicely and idles great. It sounds good and seems to run good but it won't rev up past 1000-1200 RPMS. After flushing the tanks, blowing out the lines, changing the fuel filter, I finally just disconnected the fuel line and stuck it in a jug of nice clean, fresh fuel. It still won't rev. When driving it (up to 3rd gear) I can only get it up to 1200 RPMs or so (needle bounces a lot so I don't know exactly) and it surges. Is my injector pump shot? One more quick question (for this initial post). How do I engage 6-wheel drive? I read somewhere that 6-wheel drive is automatically engaged when the transfer case is in low but in high it has to be engaged manually? How do I do that? Thanks Bill

 

[USAFSS-ColdWarrior]

Welcome aboard

Find a bunk, stow your gear, and prepare to get underway

Congratulations on snagging a wrecker! And, although she showed up in lesser condition than advertised, it will be a great toy for you to sink lots of time and money into Hence, around here we like to call MV (military vehicle) collecting an "ADDICTION".

Since you have readily admitted a profound lack of knowledge of these trucks, I might as well be the first to suggest that you go to the TM Forum on this website and start reading (and if you wish, PRINTING) the applicable TM's (Technical Manuals) for the M816 and the whole family of M8xx series 5-Ton Trucks. (Many features and equipment are common in the family.)

The TM's are the very same documents provided to the 120 lb. 18-year-old kids that Uncle Sam entrusted these vehicles to when they were in the service of this nation, and they are crammed full of great information.

As I mentioned above about finding a bunk..... While you're kicked back during rest periods you will have time to do lots and lots of reading and learning all about your truck.

I STRONGLY ADVISE that your read... REALLY READ... the OPERATIONS TM BEFORE you do anything else. This is for your own SAFETY and for the SAFETY of others as well.

Others will likely be chiming in soon with answers to your specific questions. The Member here are chock full of experience, tips, tricks, and techniques that they have picked up along the way.

Again.... WELCOME ABOARD ! ! !

John
SS Chaplain
San Angelo, Texas, USA

PS: The links below will tell you about the MV's that Dianna and I have, and lead to into the Chaplain's Corner as well.

 

[eric67camino]

Welcome to the site.

I'm sure others will chime in with better answer's soon, but I think there is a governor to keep the rpms down some when running the wrecker part. I believe there is a lever of some sort in the wrecker controls that must be disengaged to go back to normal.

And the transfer case should always be in 6wd. There is a sprag clutch in the case that engages the front axle when the rear's slip.

 

[country]

Seems you have issue with your injection pump Governor- see on back end of the PT pump



5T-1096 | MVS Fuel Injection Pump For Cummins NHC250 PT Style with Air Governor
Fuel Injection Pump For Cummins NHC-250 PT Style for M816 and M936A1 Wreckers
NSN #: 2910-01-218-5158
Part #: 3045424 3045424-9254
Price: $1,700.00

 

[BillTWD]

Welcome to the site.

I'm sure others will chime in with better answer's soon, but I think there is a governor to keep the rpms down some when running the wrecker part. I believe there is a lever of some sort in the wrecker controls that must be disengaged to go back to normal.

And the transfer case should always be in 6wd. There is a sprag clutch in the case that engages the front axle when the rear's slip.

We had several inches of snow last weekend. I took the truck out for a short drive. I rounded a corner and the back end of the truck went into a power-slide. The rear wheels were spinning but the front wheels were not. As for the possibility of a governor to disengage - it looks as if I'll be spending some time in the TM section... so much fun (sarcastically).

 

[BillTWD]

Welcome aboard

Find a bunk, stow your gear, and prepare to get underway

Congratulations on snagging a wrecker! And, although she showed up in lesser condition than advertised, it will be a great toy for you to sink lots of time and money into Hence, around here we like to call MV (military vehicle) collecting an "ADDICTION".

Since you have readily admitted a profound lack of knowledge of these trucks, I might as well be the first to suggest that you go to the TM Forum on this website and start reading (and if you wish, PRINTING) the applicable TM's (Technical Manuals) for the M816 and the whole family of M8xx series 5-Ton Trucks. (Many features and equipment are common in the family.)

The TM's are the very same documents provided to the 120 lb. 18-year-old kids that Uncle Sam entrusted these vehicles to when they were in the service of this nation, and they are crammed full of great information.

As I mentioned above about finding a bunk..... While you're kicked back during rest periods you will have time to do lots and lots of reading and learning all about your truck.

I STRONGLY ADVISE that your read... REALLY READ... the OPERATIONS TM BEFORE you do anything else. This is for your own SAFETY and for the SAFETY of others as well.

Others will likely be chiming in soon with answers to your specific questions. The Member here are chock full of experience, tips, tricks, and techniques that they have picked up along the way.

Again.... WELCOME ABOARD ! ! !

John
SS Chaplain
San Angelo, Texas, USA

PS: The links below will tell you about the MV's that Dianna and I have, and lead to into the Chaplain's Corner as well.

That's great advice that I fully intend to follow. Unfortunately, I am unable to find any TMs for the M816 in the TM section. Perhaps I'm not looking in the right place.

 

[eric67camino]

We had several inches of snow last weekend. I took the truck out for a short drive. I rounded a corner and the back end of the truck went into a power-slide. The rear wheels were spinning but the front wheels were not. As for the possibility of a governor to disengage - it looks as if I'll be spending some time in the TM section... so much fun (sarcastically).

I believe that the sprag is actually comprised of 2 one way clutches and is air operated. When you shift in to a forward gear it slides to the one clutch, when you shift to reverse, it shift's to the other. Should hear a clunk when doing so. If the sprag has failed, it won't engage the front axle.

I've also heard of installing an air-shift style switch to cut off the sprag shifter air supply, thus preventing the damage that can be caused by a roll back. Could be what was meant by engaging the 6wd.

 

[eric67camino]

That's great advice that I fully intend to follow. Unfortunately, I am unable to find any TMs for the M816 in the TM section. Perhaps I'm not looking in the right place.

The 816 falls under the 809 series of trucks.

TM's for M809 Series 5-Tons

I have uploaded the instructions for installation of cab reinforcement kit 5705616. The cab plate mounted on the rear wall designed for M44 series vehicles (M35A2, M35A3), abd M809 series vehicles.

www.steelsoldiers.com

 

[country]

Manuals on CD

M809 Series Truck 5 Ton 6X6 Repair and Maintenance Manuals

Service / Repair / Operator / Manuals on CD for M809 Series 5-Ton Truck

www.easternsurplus.net

 

[zebedee]

Welcome to the club (wrecker owners). You'll have plenty of time as we head on into winter, to read the TM's and the many great threads on wreckers, which I always enjoy when someone refreshes a topic to something that has been forgotten.
If you come across posts from Ron (RIP)[**M819] - take heed of his wise words, he had decades of in/out of service experience and the rest of us sat like new school kids on our first day in class when he took the stage.....

 

[BillTWD]

Welcome to the site.

I'm sure others will chime in with better answer's soon, but I think there is a governor to keep the rpms down some when running the wrecker part. I believe there is a lever of some sort in the wrecker controls that must be disengaged to go back to normal.

And the transfer case should always be in 6wd. There is a sprag clutch in the case that engages the front axle when the rear's slip.

There are controls near the rear of the wrecker bed for the crane drive controls. I got under the truck and found that there is a valve with an air line under the controls. I followed the air line all the way forward to the injector pump. Since the control levers are "stiff" I disconnected the arm on the valve (with the engine running) and tried revving up the engine with that arm in various positions. Nothing changed. I was still maxing out somewhere between 1000 & 1200ish RPMs... Even after browsing through many of the TMs I'm not sure what I'm looking at or if I'm even barking up the right tree. I'm considering taking the injector pump apart (even though I have almost no idea what I'm doing) and seeing if it's dirty and/or clogged up or something. What could possibly go wrong... right

 

[fasttruck]

The applicable TMs for a M 816 are: TM9-2320-260- 10, operators manual, -20 organizational maintenance manual, -20P organizational parts book, -20LO - lubrication order. There are almost 100 grease points on a M816; neglect them at your own peril. 4 on the handbrake alone. As post 2 suggests, read the reading. Several posts make reference to the throttle control on the crane which preempts the ones in the cab. M 816s have a unique fuel pump which holds the crane to a steady RPM when the crane is working. There is a control for this along with the crane clutch and crane/winch side of the power divider on the deck forward of the rear winch. You need to be familiar with these items which are described in the operrators' manual to safely operate the crane.

 

[Floridianson]

When you shift in to a forward gear it slides to the one clutch, when you shift to reverse, it shift's to the other.

Do believe when you come out of reverse to neutral it switches and when you go from neutral to reverse is switches. Some use to say you had to put in in first gear first to get it to switch but that is not correct.

 

[Floridianson]

As for the Aux. governor on top of the PT. It should be easy enough to look and the air ram on the PT and the linkage it pushes on to see if it is stuck on. The air ram pushes the PT Aux. linkage forward and if I remember there should be a small gap between the ram and leaver when disengaged.

 

[BillTWD]

As for the Aux. governor on top of the PT. It should be easy enough to look and the air ram on the PT and the linkage it pushes on to see if it is stuck on. The air ram pushes the PT Aux. linkage forward and if I remember there should be a small gap between the ram and leaver when disengaged.

Yes, I found that linkage and "messed" with it a little bit. The ram does push the linkage arm. There is a gap between the ram and the lever. The gap was 1/2 inch or so wide.

 

[Floridianson]

Just thinking was that check with the truck aired up? Wonder if the valve is leaking air to the ram? I never had any problems with mine but.

 

[BillTWD]

Ironically, there's an upside to purchasing an old gem that needs more work than anticipated. It's kind of a blessing in disguise because it forces us to learn more about the vehicle than we might have if everything already worked perfectly. I haven't mastered the fuel system by any means but I have made progress. The governor was "gummed up (for lack of a better term) . I got is loosened up and now the engine roars.

Now it's time to move on to other issues. The next topic is going to challenge my intellect. ELECTRICAL. If this were a 1972 Chevy Blazer (which I do have) with a 12 volt system I'd be good-to-go. These military 24 volt systems however just blow my mind. Basically, I just need to make all the lights, blinkers, switches and heater fan work. I might be able to stumble my way through it on my own but any tips, tricks, advice would be much appreciated. I've only attempted to work on a 24 volt system once before (a 1952 Dodge Army truck) and it could have just as well been quantum physics because I was totally and completely lost from the get-go.

 

[Guyfang]

There is no difference between 24 and 12 volts, other then the 24 volts is 12 volts higher. Just think of it as a STRONG 12 volts.

First step is to, and I know you are getting tired of hearing this, but read the operators TM. The standard army light switch has confounded soldiers for about 1000 years, I know, it happened to me. KNOWING how to turn on what you want, is half the fight.

Turn on all the lights and see what will, and what will not work, Then the heater fan, if it has one. And so on. Make a list. Helps if you can draft some wayward hobo, to watch the lights, as you go through switching them on and off. I am sure you have a multimeter and can use it. The wires are all SUPPOSED to be marked with metal tags on the ends. I would take a digital copy of the wire diagram, (its in the TM) to a print shop and tell them you want a larger sized copy of the wire diagrams and schematics. Get them coated with plastic, and I would get two copy's. At least. I love paper TM, so would just do all the TM's, but that might be costly. When I was a contractor, I had a lap top. That's all it had on it. TM's.

When working with the TM, and the worst and somewhat confusing will be the -24P's, is that ALL models are in the book. So sometimes its confusing as to just what part you might need. Here again, read the TM. It tells you how to KNOW the difference, not guess. That's what a UOC is. Usable On Code. READ.

I am not a truck guy. I did generators. But had to help the truck guys sometimes with electrical problems. This truck is not bad at all, for electrical work. Just got to get smart and take your time.

If you start taking things apart, the connectors between the wire harness and components are rubber "thingies". Use care and not brute force to get them apart. When you put them back together, a dab of silicone grease protects them, and makes it easy to replace and remove them again.

Ground is all importent on these trucks. Before you start, pull the battery's out. Clean them. Service them, if they are lead acid. Charge them, with a GOOD charger. Load test and or test the CCA on them. They are where it all starts, so make sure they are in GOOD condition. Then look at the battery connections. Clean/replace them if needed. Then hook up the battery's, IAW, (In Accordance With) the TM. Got to tell you, fooling with the battery's, can lead to exciting experiences, if done incorrectly. Take your time, do it right.

If you can fix a Landy, you can fix this truck.

 

[Ajax MD]

24 is just a number.

What will mess with your head is the lack of color-coding and the need to located and clean all the tiny metal tags so that you can identify the wires and circuits. The wiring diagrams are not outstanding but they are adequate if you can get a clear copy of them.

 

[BillTWD]

The light switch seemed to be missing when the truck first arrived. The hole on the dash for the switch was empty and the plug/connector was just hanging there. After rummaging through the mess left inside the cab I came across this light switch (picture). I assume it's aftermarket. It's push button and there's a little round blue light on each button. When I plug this switch into the truck (with the battery switch on) the lights on the truck come on (one headlight, a brake light, the panel lights...). This happens without pushing any of the buttons on the switch. In fact, pushing the buttons (any of them) has no affect at all (they do nothing). If I ground the switch, the blue lights on the buttons all come on and start blinking but still don't actually control anything.