M1083 CTIS issue

Hello all,

I'm a new member here in hopes on helping myself and our mechanic figure out our LMTV issues.

It's to be our new firefighting rig (Florida Forest Service) and currently has a 900 gallon tank with a hatz diesel high volume pump to feed our three manifolds plus booster reel.

That aside, the CTIS system has been literally killing me every day. Upon start up, the highway light will blink once like it's about to do self check, then nothing. When you depress a button it will light up but no release or fill, there are no trouble lights to be had; Yet it will not air the tires up or release air.

I'm getting air to the main line and have air to the ?manifold? behind the passenger kick panel. Jumping the controller plug in I can make the system dump air, and when jumping the control pin the relay clicks, but it will not fill anything. Does this sound like a bad ?manifold? (Whatever the correct term is behind that kick panel)

We've been searching TMs like there's gold or the winning Powerball numbers in there and can't seem to figure it out so I figured I'd reach out to y'all in hopes of figuring this all out.

Thanks in advance.

Check for valve stems in tires

Coffey1 said:

Check for valve stems in tires

Click to expand...

Should it have or not have valve stems? All six have stems in them.

Valve stems, yes. Valve cores, no.

Jbulach said:

Valve stems, yes. Valve cores, no.

Click to expand...

Yes, it has cores on all six from looking at it just now. Should I try pulling and re-engage the CTIS? We get all our equipment from Lake City (when we're lucky) so maybe they just didn't understand it? I pulled one the other day just to see if it would lose air and it didn't. Valve cores would keep the CTIS from inflating?

So, I have one tire that doesn't lose air when I pull the valve core, the other five lose air. Currently have one tire on the ground and the CTIS ain't having it.

So, I have one tire that doesn't lose air when I pull the valve core, the other five lose air. Currently have one tire on the ground and the CTIS ain't having it.

When you start the truck, hwy should flash until there is around 100psi in the tanks. At which time a pressure switch closes and the system should do an initial pressure test and decide if it should fill, dump or do nothing. If the hwy light only flashes onces when you start the truck and no lights show on the display after that it sounds like a controller issue. The one tire that dosnt loose air when you remove the valve core could be something plugged up or someone could have put a schrader valve in the valve stem.

Yep, I think you’re pulling the wrong valve cores. The five that loose air when you pull the valve core out of the wheel valve should be good. The one that is not losing air, unless the tire has no air to loose, may have a valve core installed in the valve stem of the wheel, that the CTIS hose is attached to. As suprman said you have other problems

Mine has valve stems and valve cores(schrader valve) installed in them and the CTIS system inflates and deflates the tires just fine...

you have 3 solenoid valves on the pressure control unit(PCU) manifold behind the passenger kick plate.

The control solenoid is normally open and vents the PCU main gallery and all the CTIS plumbing to the atmosphere. Activating it closes the valve and allows the system to hold air.

The supply solenoid is normally closed and when activated it opens and allows supply air from the wet tank protection valve to enter the PCU manifold and pressurize the system.

The deflate valve is normally closed and when open vents the PCU gallery thru a 9PSI relief valve.

The PCU gallery is connected to the main line that runs down to the wheels. It T’s on the passenger side of the transmission and goes fore and aft to dump valves and on to the wheels.

The wheel valves are a large diaphragm on the supply side that controls a small port to the tire in the middle. Air from the system 7-8PSI will push the diaphragm and open the wheel port. As long as at least 7-8PSI is maintained on the supply side air can be put into and released from the tire thru this valve. The valve stems on mine are on the tire side of this wheel valve and are “T’d ” into the system so you can also add or remove air at the wheel.

You need 2 PCU solenoid valves to operate properly. Control plus a brief shot of Supply pressurizes the system and opens the wheel valves. This allows the system to read tire pressure as long as the control solenoid is maintained. When control is opened system pressure is vented, the dump valves vent briefly and the wheel valves close.

Control + Supply and the wheels inflate as long as supply is greater than wheel pressure.

Control + a shot of Supply to pressurize the system and open the wheel valves, then while still holding control, activate Deflate and the plumbing is vented thru that relief valve that acts as a regulator to hold the system at about 9PSI. This decrease shifts the dump valves to dump while still keeping the wheel valves open and the tires deflate thru the dump valves.

Like Suprman said Nothing happens until wet tank pressure is reached. There is a switch on the back side of the tank that closes at around 115 PSI and opens again at about 85 PSI. This tells CTIS that it has air pressure to work with and also forces the system to top off the wet tank occasionally to maintain brake pressure. The protection valve(looks like a regulator below the pressure switch) also halts airflow to CTIS when the tank pressure drops to around 85 PSI to save air for the braking system.

You can jumper the CTIS solenoids and check manifold function and check for leaks. Sounds like you already know how to do that, you just need to use the right combinations. Be careful manually inflating, an over-inflated 48” split rim is death on a stick...

For overall function I would start with checking the wet tank pressure. You can unscrew the drain valve and screw in a gauge. I am able to check tank pressures without removing the valve using an air gun with a rubber tip and a gauge connected where an air hose would normally go. Push the tip against the drain hole and open the drain valve and squeeze the air gun valve and you can read tank pressure. Check that wet tank pressure is reaching 120 PSI(if your brakes are, it probably is) if not you need to adjust the governor up on the air compressor to get 120 into the system. Once you can cycle the tank between 85 and 120, you can hook an ohm meter to the 2 pins on the pressure switch and check that the switch is closing(short) at 115ish and re-opening below 90PSI...

That switch must cycle properly for CTIS to operate...

If you don't hear any solenoid clicking means that the system is not ready. Most probably as Ronmar wrote the wet air tank sensor...

Lifehiker said:

Hello all,

I'm a new member here in hopes on helping myself and our mechanic figure out our LMTV issues.

It's to be our new firefighting rig (Florida Forest Service) and currently has a 900 gallon tank with a hatz diesel high volume pump to feed our three manifolds plus booster reel.

That aside, the CTIS system has been literally killing me every day. Upon start up, the highway light will blink once like it's about to do self check, then nothing. When you depress a button it will light up but no release or fill, there are no trouble lights to be had; Yet it will not air the tires up or release air.

I'm getting air to the main line and have air to the ?manifold? behind the passenger kick panel. Jumping the controller plug in I can make the system dump air, and when jumping the control pin the relay clicks, but it will not fill anything. Does this sound like a bad ?manifold? (Whatever the correct term is behind that kick panel)

We've been searching TMs like there's gold or the winning Powerball numbers in there and can't seem to figure it out so I figured I'd reach out to y'all in hopes of figuring this all out.

Thanks in advance.

Click to expand...

Where are you out of? FFS here as well. Have been working the kinks out of our MTV for a while. Not done yet lol. If your truck is an LMTV (single rear axle) like you say, it is way overloaded with a 900 gallon tank. LMTV is rated for 5,000 pounds. Water is 8.3 lbs/gallon. 8.3x900=7470lbs, not counting the weight of your tank, pump, hoses, etc. If you have an MTV (2 rear axles, 10,000lb rating) like mine, you are good to go. I have a 1025 gallon tank. The tank weighs 300lbs. 1025x8.3+300=8,807.5lbs. I also got a Hatz diesel from Lake City, but couldn't get it to run. Got a Honda.

M1083 said:

Where are you out of? FFS here as well. Have been working the kinks out of our MTV for a while. Not done yet lol. If your truck is an LMTV (single rear axle) like you say, it is way overloaded with a 900 gallon tank. LMTV is rated for 5,000 pounds. Water is 8.3 lbs/gallon. 8.3x900=7470lbs, not counting the weight of your tank, pump, hoses, etc. If you have an MTV (2 rear axles, 10,000lb rating) like mine, you are good to go. I have a 1025 gallon tank. The tank weighs 300lbs. 1025x8.3+300=8,807.5lbs. I also got a Hatz diesel from Lake City, but couldn't get it to run. Got a Honda.

Click to expand...

6 tires = 5ton...