Working on the M1078 LMTV

[snowtrac nome]

I just read something about this in one of the 5 ton ctis threads had something to do with tires not inflated equaly forget what it was the guy who posted it was a rep from the company that builds the system

 

[Andyrv6av8r]

Everything was working fine when it was parked a couple of days after my knee injury. Keith_J came over and repositioned both the 1078 and my deuce as I had moved them the day of the accident so he put everything back in place for me. The truck has since been sitting for about 6 weeks. The dump valve and the 5 flashing lights were going on at the same time. I tried shutting the truck down and airing up the tires with my shop compressor but the valve remained open letting air out.

Maybe your deflate solenoid in the PCU got stuck in the open position. But it doesn't explain while only the QRV for the front axle stayed open after shutting the truck off. Are you sure that the rear tires didn't deflate as well? They will look more inflated because of less weight on the rear of the truck.

 

[mkcoen]

Maybe your deflate solenoid in the PCU got stuck in the open position. But it doesn't explain while only the QRV for the front axle stayed open after shutting the truck off. Are you sure that the rear tires didn't deflate as well? They will look more inflated because of less weight on the rear of the truck.

Yeh I went out this morning and the rears were flat as well. Guess the fronts just deflated immediately and it took a bit for the rears to go down.

 

[mkcoen]

So after physical therapy this morning thought I'd try starting the truck again to see if it was a stuck and not bad valve. Hit Emergency on the CTIS and every thing started filling up. Switched to Highway once the air tanks were full and it looked like it was going to self correct. Up until the tires were inflated and the system did a check and then "boom" valve sticks open and dumps the air again. Five flashing lights on the controller again too.

 

[mkcoen]

Well the TMs don't seem to be much help in this matter. Here's what's going on while I try and troubleshoot things:

1) With air tanks empty I can start the truck and then set the CTIS to Run Flat
2) Air tanks air up, tires eventually start airing up
3) Manifold makes appropriate clicking noises
4) Once CTIS gets to the point that it does self test (at this time tires are almost fully aired) it starts dumping air and flashing all five lights - unable to select anything on controller now
5) Attempted to do entire cycle but shut truck off when tires were about 35PSI and system started dumping air immediately

I have found no leaks anywhere in the system and the valves appear to be working properly during the air up sequence.


***************

Went back and let the truck sit running in Run Flat mode. Air tires up completely and automatically switched to Highway. Cycled through a couple of times dropping the air pressure then finally defaulted back to 5 flashing lights and started venting.

 

[Coffey1]

That's the same thing mine is doing except it won't deflate them to flat.
Mine likes to dump air until all tires are 32psi then everything stops 5 flashers and not able to select any thing.
Same when you restart the tires get to about 50 then starts dumping until they are back to 32

 

[Suprman]

If you are leaking down with the truck off I have come up with an easy way to test the wheel valves. Spray windex around the hoses and connections look for bubbles. Sometimes it's just an o ring or tighten up a hose. Take off the banjo bolt (by hand no impact) get a small plastic bag and rubber band. Put plastic bag scrunched down over banjo down to hose and rubber band tight on there. Leave for an hour or so. If air is leaking thru valve bag will expand. Wheel valves go bad they really only have a 3-4 year lifespan. The rubber inside will out-gas and this will corrode the valve metal. You can get some dirt in the valve and it won't seal right. The control body sends around 12 psi to hold the wheel valves open and dump. If you have the controller unplugged and you are still dumping air chances are something is going on with a wheel valve not seating properly.

 

[Suprman]

If more than one tire is pretty much flat the system has a hard time dealing with that. You will have to air up somewhat manually then see if the system will let you press highway and run flat and air up. All 5 lights is a hardware fault it shouldn't be sending air.

 

[Coffey1]

I guess my wheel valves are ok tires stay at 60psi as long as I don't connect euc and start truck.

 

[Coffey1]

I'm leaning towards pcu being bad.
I put a good known working euc in and it won't even light up.
And my euc is also suspect.

 

[mkcoen]

Its not a leaking issue, the dump valves are staying open and thats what is causing the tires to go flat. The question is what is causing the valves to stay open?

 

[wheelspinner]

If you are leaking down with the truck off I have come up with an easy way to test the wheel valves. Spray windex around the hoses and connections look for bubbles. Sometimes it's just an o ring or tighten up a hose. Take off the banjo bolt (by hand no impact) get a small plastic bag and rubber band. Put plastic bag scrunched down over banjo down to hose and rubber band tight on there. Leave for an hour or so. If air is leaking thru valve bag will expand. Wheel valves go bad they really only have a 3-4 year lifespan. The rubber inside will out-gas and this will corrode the valve metal. You can get some dirt in the valve and it won't seal right. The control body sends around 12 psi to hold the wheel valves open and dump. If you have the controller unplugged and you are still dumping air chances are something is going on with a wheel valve not seating properly.

Will are the valves rebuild able?

 

[Coffey1]

Again I believe it to be the pcu.
I will put a known working one in this weekend hopefully and see if it stops my dump valves from dumping.

 

[Stellaevil]

Yeh I went out this morning and the rears were flat as well. Guess the fronts just deflated immediately and it took a bit for the rears to go down.

When the CTIS checks the tire pressures: The upper control line (pCU to QRV tops, must stay above the tire pressures or they will dump. Things that can cause this.....1. Imbalanced or flat tires when the pressure switch opens(run the engine at FT to close it quicker. 2. Leaking upper line, keeps dropping below the tire pressure. 3. Pressure switch closes too soon, supply lower than the tires. If PCU is deflating tires all the tires will deflate and air will be coming out the PCU vent.

 

[mkcoen]

My fix was to air the tires up, disconnect the CTIS controller, start the truck to verify nothing then dumped the re-filled tires. It would be nice to have a working CTIS but I'm not in a place financially to start dumping more money into the truck. If I take it to Big Bend in Oct then I might worry about being able to adjust the air in the tires but while it's sitting in the driveway or doing local shows there's no need to get it beyond being able to start, drive, and stop.

 

[TexAndy]

On my deuce, I just installed a regulator set to 50 psi and QD fitting on the under dash air port. That way I can just stick the air hose on to the tire and walk away.

That's what I'll probably do on my 923a2. The CTIS just doesn't seem all that convenient for what it would probably take to get it working again.

 

[Another Ahab]

On my deuce, I just installed a regulator set to 50 psi and QD fitting on the under dash air port. That way I can just stick the air hose on to the tire and walk away.

That's what I'll probably do on my 923a2. The CTIS just doesn't seem all that convenient for what it would probably take to get it working again.

The CTIS must be a real nice feature when it's working, but it sure does seem to present a lot of problems based on all the various comments on all the various threads.

 

[coachgeo]

The CTIS must be a real nice feature when it's working, but it sure does seem to present a lot of problems based on all the various comments on all the various threads.

More and more why I like the simplified system that has been built by a member here. All Neumatic........ no computer to FUBAR and easy to understand how it works thus easy to troubleshoot and repair if needed.

http://www.steelsoldiers.com/showthread.php?161829-Manual-CTIS-control-how-to which refers to this one.... http://www.steelsoldiers.com/showthread.php?152581-Manual-CTIS-Conversion-for-M-1078

 

[coachgeo]

On my deuce, I just installed a regulator set to 50 psi and QD fitting on the under dash air port. That way I can just stick the air hose on to the tire and walk away....

little confused...... you say quick disconnect installed under dash with regulator...... then you ssay you put air hose on tire? Did you mean to say you put air hose on the QD under the dash?

 

[TexAndy]

little confused...... you say quick disconnect installed under dash with regulator...... then you ssay you put air hose on tire? Did you mean to say you put air hose on the QD under the dash?

I put the air hose on top of the tire. It inflates by magic.