Hooking LMTV to shop air for CTIS troubleshooting

[Lostchain]

Hey all. Has anyone had experience hooking their LMTV to shop air so that they can troubleshoot air issues without the engine running?

I tried hooking up to the front service gladhand, but the system didn’t take much air. I looked at the pneumatic schematic in the TM and I think maybe that’s because I didn’t release the parking brake. Can anyone confirm this?

Also, my shop air is 175 psi. Would this pose a problem for the system or should I regulate it down to 120?

thanks!

 

[NDT]

Need to feed the emergency gladhand with 120 psi. Or remove the wet tank drain valve and attach a quick coupler.

 

[MrMikey4026]

Yes, I used an automotive cylinder leak down tester plumbed in at the pressure control module. Connect to the line going to the line supplying the tires.
It worked great, use soap suds to check for leaks.
You can run the pressure up and down to test the operation of the wheel valves and quick release valves. You can also connect to the wet tank at the drain valve, do not exceed 125 psi.

 

[Ronmar]

Yep, front emergency(red) glad-hand charges the truck air system. use a regulator set to 120 PSI. It also releases the park brake, so chock the wheels…

Applying air to the front blue service glad-hand applies the service brakes.

The problem with troubleshooting CTIS is it works in cycles, so you only get pressurized windows in which to look for leaks/issues.

It is far easier to evaluate the system by either pressurizing the system by connecting to the PCU output port(feeds the rest of the system) with a regulator set to an acceptable tire pressure as mentioned above. This method does not test the PCU though but it is great for finding leaks…

Or jumpering 24V (H) to the control solenoid(R) in the CTIS controller connector to seal the system, and momentarily jumping 24V(H) to the supply solenoid pin (B) to give it a shot of air. Do not leave the supply solenoid powered, as you can over-inflate the tires(big bada boom).

The shot of air will open the wheel valves and the system will set at tire pressure while you quietly look, listen and feel for leaks. I found all kinds of leaks once the cat wasn’t purring in my ear…

Once pressurized, As long as the control solenoid is powered(H to R) to keep the system sealed, the system should set at pressure, unless you have a really bad leak pulling the control jumper or turning off the main switch will vent the system.



These are the basis of my manual control system. Here is how it works with switches connecting 24V(H) to control, inflate and deflate(R,B &C)

 

[chucky]

Yep, front emergency(red) glad-hand charges the truck air system. use a regulator set to 120 PSI. It also releases the park brake, so chock the wheels…

Applying air to the front blue service glad-hand applies the service brakes.

The problem with troubleshooting CTIS is it works in cycles, so you only get pressurized windows in which to look for leaks/issues.

It is far easier to evaluate the system by either pressurizing the system by connecting to the PCU output port(feeds the rest of the system) with a regulator set to an acceptable tire pressure as mentioned above. This method does not test the PCU though but it is great for finding leaks…

Or jumpering 24V (H) to the control solenoid(R) in the CTIS controller connector to seal the system, and momentarily jumping 24V(H) to the supply solenoid pin (B) to give it a shot of air. Do not leave the supply solenoid powered, as you can over-inflate the tires(big bada boom).

The shot of air will open the wheel valves and the system will set at tire pressure while you quietly look, listen and feel for leaks. I found all kinds of leaks once the cat wasn’t purring in my ear…

Once pressurized, As long as the control solenoid is powered(H to R) to keep the system sealed, the system should set at pressure, unless you have a really bad leak pulling the control jumper or turning off the main switch will vent the system.

View attachment 868089

These are the basis of my manual control system. Here is how it works with switches connecting 24V(H) to control, inflate and deflate(R,B &C)

Do you make/sale these manual ctis boxes? If so let me know . Thanks

 

[Guruman]

I've been meaning to ask about using shop air myself. I've had my shop air connected to the front "emergency" glad had to release the brake to aid in removing and installing the drive shafts recently.

When the shop air is connected, I get a bit of air leaking out somewhere near the left headlight. but,... without the shopper hooked up, and the truck is pressurized, I hear no leaking from there. ???

I was considering removing the front glad-hands altogether, but I thought it washed that it only leaked noticeably when connected to shop air. Maybe someone can explain why that is?

 

[Lostchain]

Yep, front emergency(red) glad-hand charges the truck air system. use a regulator set to 120 PSI. It also releases the park brake, so chock the wheels…

Applying air to the front blue service glad-hand applies the service brakes.

The problem with troubleshooting CTIS is it works in cycles, so you only get pressurized windows in which to look for leaks/issues.

Thanks for all the helpful info, that manual controller looks pretty sweet! Good job on that.
that being said, I do have the Dana Diagnostic Tool which has an option for test and hold (among other things) that will allow for in-depth troubleshooting. This is why I want to run the truck off the shop air. I am currently fighting a “4 lights blinking” code 44 ( tire imbalance) and none of the tires or hoses or fittings that I can find are leaking.

 

[Mullaney]

I've been meaning to ask about using shop air myself. I've had my shop air connected to the front "emergency" glad had to release the brake to aid in removing and installing the drive shafts recently.

When the shop air is connected, I get a bit of air leaking out somewhere near the left headlight. but,... without the shopper hooked up, and the truck is pressurized, I hear no leaking from there. ???

I was considering removing the front glad-hands altogether, but I thought it washed that it only leaked noticeably when connected to shop air. Maybe someone can explain why that is?

.
I would suggest that you keep the front glad hands. If the truck ever breaks down, even regular commercial wreckers can hook up to those connectors. Having them also releases your brakes (the spring brakes) so the wrecker driver doesn't have to crawl under your truck to "cage the brakes".

With 120# of shop air and a spray bottle of soapy water, you can find the air leaks. Driver's Side charges the air system. Passenger Side applies the brakes when being towed.

 

[Ronmar]

.
I would suggest that you keep the front glad hands. If the truck ever breaks down, even regular commercial wreckers can hook up to those connectors. Having them also releases your brakes (the spring brakes) so the wrecker driver doesn't have to crawl under your truck to "cage the brakes".

With 120# of shop air and a spray bottle of soapy water, you can find the air leaks. Driver's Side charges the air system. Passenger Side applies the brakes when being towed.

Think you got that backwards. The emer gladhand that pressurizes the system and releases the park brake is on the passenger side

service glad-hand that applies the service brakes is on the drivers side…

 

[Ronmar]

I've been meaning to ask about using shop air myself. I've had my shop air connected to the front "emergency" glad had to release the brake to aid in removing and installing the drive shafts recently.

When the shop air is connected, I get a bit of air leaking out somewhere near the left headlight. but,... without the shopper hooked up, and the truck is pressurized, I hear no leaking from there. ???

I was considering removing the front glad-hands altogether, but I thought it washed that it only leaked noticeably when connected to shop air. Maybe someone can explain why that is?

The front red/emer glad-hand feeds two places.
1. Thru a check valve to charge the wet tank.
2. The upper 2way behind the drivers grill/behind drivers step. Sounds like tgat second line or the fitting at the 2way is leaking…. It only sees pressure when you feed air into the emergency glad-hand.

 

[Guruman]

.
I would suggest that you keep the front glad hands. If the truck ever breaks down, even regular commercial wreckers can hook up to those connectors. Having them also releases your brakes (the spring brakes) so the wrecker driver doesn't have to crawl under your truck to "cage the brakes".

With 120# of shop air and a spray bottle of soapy water, you can find the air leaks. Driver's Side charges the air system. Passenger Side applies the brakes when being towed.

Admittedly I did not try too hard, but at first pass it was not easy to get to wherever it was leaking. Plus I was working on something else at the time. Maybe I'll give it another pass before yanking everything out.

 

[gslader]

To pile onto this thread. I'm planning on adding "T" at the wet air tank where the elbow currently is before the pressure protection valve. My question to this group is whether anyone knows what size "T" I would need (my truck is not stored at my house). Is it just a 1/4" female NPT Tee?

 

[Ronmar]

To pile onto this thread. I'm planning on adding "T" at the wet air tank where the elbow currently is before the pressure protection valve. My question to this group is whether anyone knows what size "T" I would need (my truck is not stored at my house). Is it just a 1/4" female NPT Tee?

I put a street T right above that point where the CTIS pressure switch is located. That was a little easier and is 1/4” NPT…

 

[ramdough]

I put a street T right above that point where the CTIS pressure switch is located. That was a little easier and is 1/4” NPT…

Any issue with shop air not going through your truck air dryer?

My compressor does ok, but when using a lot of air (painting), I eventually get some water droplets. I will eventually upgrade the drying part once I plumb it into my shop.

So far, my truck dryer works great….. never any water or oil in my wet tank.

Would it make any sense to tee into the inlet fitting there?


Sent from my iPhone using Tapatalk

 

[Ronmar]

Hooked to the ctis port on the wet tank the air will get a chance to shed moisture in that tank. The times I have applied air to the truck I have not noticed any moisture buildup in the wet tank, but other than when filling tires I havnt run all that much shop air thru it..

 

[GeneralDisorder]

I would regulate the shop pressure down to 90 psi to avoid over-inflating the tires.

 

[Lostchain]

I would regulate the shop pressure down to 90 psi to avoid over-inflating the tires.

Yeah I am going to go to Harbor Garbage tomorrow and buy a regulator.. I got a little impatient last night and hooked it up to the shop air as-is and while no hoses blew off, there were some creaks and groans, so I hope I didn't do any damage...

 

[Lostchain]

Or jumpering 24V (H) to the control solenoid(R) in the CTIS controller connector to seal the system, and momentarily jumping 24V(H) to the supply solenoid pin (B) to give it a shot of air. Do not leave the supply solenoid powered, as you can over-inflate the tires(big bada boom).

If you energize the control solenoid but DO NOT give it a shot of air, what is supposed to happen? On my truck, as soon as you energize the control solenoid, the pressure as reported by the PCU transducer slowly rises until the tires begin to deflate out the QRVs... Is that normal? I suspect it isn't....

 

[Ronmar]

If you energize the control solenoid but DO NOT give it a shot of air, what is supposed to happen? On my truck, as soon as you energize the control solenoid, the pressure as reported by the PCU transducer slowly rises until the tires begin to deflate out the QRVs... Is that normal? I suspect it isn't....

I believe It is normal, at least the two I have played with now do it also Even after new valve cores. The supply does(should) not leak when control is de-energized. The solenoid valves in the PCU are pilot actuated and they may be plumbed to deliberately interact this way. (Would alert you to a shorted control circuit. It will dump once the pressure builds to 6-7 PSI to open the wheel valves, but the dump valves feed a little pressure back toward the PCU so that pressure will continue to build until the truck side = the tire side at which time the dump valves stop. As the pressure equalizes, The deflate will get slower and slower until it stops. It takes 25-30 seconds on mine… it will do the same thing when you halt a deliberate dump, until you give it a shot of air to equalize the truck side with the tires. I did a video of the latest version of my manual system that shows a little of that. I incorporated a latching circuit to the control so it doesn’t get energized until you push the supply, and then stays energized until you shutoff it’s power…

 

[Lostchain]

I believe It is normal, at least the two I have played with now do it also Even after new valve cores. The supply does(should) not leak when control is de-energized. The solenoid valves in the PCU are pilot actuated and they may be plumbed to deliberately interact this way. (Would alert you to a shorted control circuit. It will dump once the pressure builds to 6-7 PSI to open the wheel valves, but the dump valves feed a little pressure back toward the PCU so that pressure will continue to build until the truck side = the tire side at which time the dump valves stop. As the pressure equalizes, The deflate will get slower and slower until it stops. It takes 25-30 seconds on mine… it will do the same thing when you halt a deliberate dump, until you give it a shot of air to equalize the truck side with the tires. I did a video of the latest version of my manual system that shows a little of that. I incorporated a latching circuit to the control so it doesn’t get energized until you push the supply, and then stays energized until you shutoff it’s power…

On your video, if you send the shot of air and then let go, you are able to observe your tire pressure and the pressure in the control lines stays stable.
On my truck, the pressure in the control lines does not stay stable. It is always dropping. I do have some slight leaks around my wheel valves during inflate but they do not leak at rest. The interesting thing is that it happens worse at higher air pressures. usually below 40, the control lines hold pressure, but at 55 and above, the lines will not hold pressure, and the effect of this is a 4 blinking light tire imbalance code set.

Would a leak at the wheel valves cause the pressure in the lines between the PCU and the QRVs do be unstable?