CTIS Theory questions.

[Dodge man]

Despite the offer of CM to troubleshoot my truck (blah, blah,blah) and that 'we are making additional and lower level manuals for the military' - no data has been forthcoming.

You should offer to review and proof their draft manuals! IF you agreed to sign a Non-Disclosure Agreement I'll bet they'd go for it. That's something that contractors are usually required to do anyway and it usually cost them a ton of money. Heck, with a good, persuasive argument you might even get them to hire you as a consultant for a modest amount of money!

All in all, it sounds like they've been reasonable. They're at least talking to you, with most companies you wouldn't have gotten past the telephone answering droid.

 

[Rustygears]

1. They communicated ONCE via their email and never replied since
2. If I execute an NDA, I cannot help other people troubleshoot their CTIS. That defeats the stated purpose of my reason for contacting them
3. NDAs are dangerous things. Clearly you've never sued or been the party to a suit over IP rights. Signing one for the sake of signing it is not a wise and mature decision because then one is contaminated with their IP info. That is a big liability unless you live in a cave without internet.

4. The quake yesterday in Tokyo was a MF! Now stranded trying to get home.

No Cali quake I've been through since the 70's comes within miles of that rollercoaster. aftershocks in mag 6 & & every few minutes all night and today. Makes a Deuce ride seem like a tour in a Rolls! Jane stop this crazy thing!

 

[bobferrin]

This last Nov I purchased my first M35A3 and was thrust into this CTIS issue as well. My system "honked" as it tried to build pressure and then read "Flat?" on the screen. I would occationally go through this initialization process but never fill tires. I have since had each of my hubs apart and replaced all of the seals. I have spent many hours testing and troubleshooting this system. I have also read everything that I could get my eyes on regarding this system and associated issues. I have even spent considerable time on the phone with engineers from C M Automotive trying to isolate and solve this problem. I have since purchased 2 more A3's one of which has a perfectly functioning CTIS system and the other not functioning but not acting like the first.

These are some of my findings in my case: The system starts out (does not matter whether the tires are full or flat) by releasing a small amount of pressure into the lines from the manifold and tests the air-tight integrity of the piping system from the manifold to the wheel valves. If there is any kind of a leak the system will falt to "Flat?" on the screen and shut down then try again periodically. If the system can fill (no line or hub leaks), It will build up pressure to overcome the wheel valve mechanism. I do not know the exact amount of pressure it takes - if it is one value or just above the actual pressure in the tire. I think it just needs to be above the pressure of the tire. At this point the wheel valve opens to the system and the manifold will fill or deflate the tires based on the controller's demands. If at some point the line were to come loose or have a large leak the wheel valve will shut down.
So the wheel valve will allow air to move out of the wheel at a controlled rate and if it is allowed to freeflow out of the tire the valve will snap shut. If you take the individual pipe loose at the axle "tee" and use compressed air to test the line out to the tire you can hear the valve open and air begin to fill the tire. If you allow air to gently bleed out, you can completely deflate the tire, but as soon as you allow the air to freeflow out of the line the valve closes. This is also a simple way to test the integrity of the hub seals. Leaks will show up by air leaking out of the little breather valves on the top of each axle or you will hear air leaking out aroung the hub/brake linings area. It really is a simple job to replace the seals.

The manifold is one open chamber on the fill side. There is 4 output ports (three piped to each axle tee, and one is plugged off. I have had the manifold off the truck with all plumbing and fittings removed and it is clear that the internal chamber is open to all 4 ports with no valving or partition between. So there is no differentiation between wheels or axles. What one tire gets they all get. If there is actual pressure differentials in the tires after the system has finished its process, I would assume there is some sort of clog in that particular branch not allowing the complete pressure to make it out to that wheel??

As far as the system purging during standby - I'm not entirely sure. I do know that when the system shuts down the system purges and closes the wheel valves. I think that when the system is active the lines are full. Not sure though.

So I am at the point on my first deuce where I have verified that there are no leaks in the system, I have replaced the manifold with a new unit and still the system will not fill and gives me this honking sound when it is trying. I'm tempted to tear into my working deuce and discover the differences but I am reluctant to put a wrench to something that is working. C M Automotive has offered to troubleshoot my manifold assy, so I may take advantage of that. I'm convinced that there is something amiss with the exhaust port/selinoid or associated wiring/connectors, or perhaps a missing internal part of some sort.

I did find somthing interesting as I tore apart the hubs. I think that the mechanic that worked on my particular deuce at the National Guard Motor Pool (no offense to any military mechanics) was not the highest trained individual. I did not know anything about these trucks, but I did know that these hubs had been taken apart and not reassembled correctly. So beware of that possibility.

Finally, I could use any advice from others that may have ideas concerning these issues. THX, Bob

 

[Stalwart]

Thats what I was trying to say, but Bob said it better.

 

[AceHigh]

My unit is now working properly after replacing some pieces parts, but the problem I am having is the air dryer unit. I replaced the filter in the dryer but it is still venting too often and when it vents the CTIS purges and goes back to zero. Due to the rapid purging I can actually lose pressure when it is supposed to fill.

To get my system to work one must be on the highway and not stop for anything until the tires are up. Each stoplight takes about 2 psi out of the system.

Thanks for the info! It is great to get a better understanding of the system.

 

[motomacguyver]

Bobferrin, I have a couple of questions/comments.

1st, I noticed in the TM that they want you to test the OHMs to ground at the controller and the manifold. Did you do this?

2nd, where did you find the seals for your hubs?

Thanks for the informative write up, this will help me troubleshot my system.

 

[Rustygears]

I have overhauled the air dryer system on my truck and entirely rebuilt it. It is a very simple system. The purge command comes directly from the compressor governor via a small airline from the governor (not the air line to the storage tank). When the compressor unloads, the dryer purges by venting the air stored in the large volume of the dryer housing in reverse direction to force the collected snot out of the dessicant cartridge.

If your dryer is purging often, this is indicative of the compressor cycling often. When the truck air system is charged to cutoff (130 - 140psi typical), the air compressor unloads (no longer compresses air by no longer cycling the intake or exhaust port valves (I forget which, I'm sitting in an airport again - hope no quakes on this trip). If there are no brakes used, no cooling fan clutch engagement, power steering usage and no CTIS, there should be no drop in indicated pressure over time. The air pressure should sit at the cutoff pressure for more than an hour with no use of these items.

When the system air pressure drops below the cut-in pressure (around 100 PSI), the compressor toggles the vent line, engages the compressor valves and the pump charges the lines and fills the tank again. You can hear when this happens because the dryer will make a quick 'ffft' sound when the purge line toggles and the purge valve closes. You can also hear the engine speed (idle) change slightly and also hear the compressor valve train noise change as it starts to labor to raise the system pressure.

If it is cycling more rapidly than once every many minutes with no brake, clutch fan, power steering or CTIS load, you have a leak. WIth all the plastic plumbing connections and those crappy snap on fittings, things get loose. Look for oily fittings and connections. That's a dead ringer for a leak point. A little soapy water dribbled on connections will also help, but the oily connection is usually pretty obvious.

The power steering system is also notorious for leaking, especially the hidden 'secret' regulator in the front driver side inside the frame 'C' rail adjacent to where the compressor mounts on the engine. There's other threads on this (including mine).

The purge (compressor cut-out/cut-in) should not have an affect on CTIS operation unless system air pressure drops below 90PSI, which is where CTIS is supposed to shut off to protect the brake function. Have a look at the dash pressure gauge when things are cutting in/out and CTIS is also resetting as you indicated. It is your main (and only) direct measurement of system condition and it will tell you quite a bit as I have outlined. This should allow you to perform a 1st level triage of the situation regarding gross leaks, etc.

Cheers!

 

[AceHigh]

Thanks, Rusty. I should have done a search of the TM, but that is a great start. I think the rapid purging is due to the CTIS demanding air. I will check for leaks. Hope the rest of your trip is uneventful.

 

[mktopside]

This last Nov I purchased my first M35A3 and was thrust into this CTIS issue as well. My system "honked" as it tried to build pressure and then read "Flat?" on the screen. I would occationally go through this initialization process but never fill tires. I have since had each of my hubs apart and replaced all of the seals. I have spent many hours testing and troubleshooting this system. I have also read everything that I could get my eyes on regarding this system and associated issues. I have even spent considerable time on the phone with engineers from C M Automotive trying to isolate and solve this problem. I have since purchased 2 more A3's one of which has a perfectly functioning CTIS system and the other not functioning but not acting like the first.

These are some of my findings in my case: The system starts out (does not matter whether the tires are full or flat) by releasing a small amount of pressure into the lines from the manifold and tests the air-tight integrity of the piping system from the manifold to the wheel valves. If there is any kind of a leak the system will falt to "Flat?" on the screen and shut down then try again periodically. If the system can fill (no line or hub leaks), It will build up pressure to overcome the wheel valve mechanism. I do not know the exact amount of pressure it takes - if it is one value or just above the actual pressure in the tire. I think it just needs to be above the pressure of the tire. At this point the wheel valve opens to the system and the manifold will fill or deflate the tires based on the controller's demands. If at some point the line were to come loose or have a large leak the wheel valve will shut down.
So the wheel valve will allow air to move out of the wheel at a controlled rate and if it is allowed to freeflow out of the tire the valve will snap shut. If you take the individual pipe loose at the axle "tee" and use compressed air to test the line out to the tire you can hear the valve open and air begin to fill the tire. If you allow air to gently bleed out, you can completely deflate the tire, but as soon as you allow the air to freeflow out of the line the valve closes. This is also a simple way to test the integrity of the hub seals. Leaks will show up by air leaking out of the little breather valves on the top of each axle or you will hear air leaking out aroung the hub/brake linings area. It really is a simple job to replace the seals.

The manifold is one open chamber on the fill side. There is 4 output ports (three piped to each axle tee, and one is plugged off. I have had the manifold off the truck with all plumbing and fittings removed and it is clear that the internal chamber is open to all 4 ports with no valving or partition between. So there is no differentiation between wheels or axles. What one tire gets they all get. If there is actual pressure differentials in the tires after the system has finished its process, I would assume there is some sort of clog in that particular branch not allowing the complete pressure to make it out to that wheel??

As far as the system purging during standby - I'm not entirely sure. I do know that when the system shuts down the system purges and closes the wheel valves. I think that when the system is active the lines are full. Not sure though.

So I am at the point on my first deuce where I have verified that there are no leaks in the system, I have replaced the manifold with a new unit and still the system will not fill and gives me this honking sound when it is trying. I'm tempted to tear into my working deuce and discover the differences but I am reluctant to put a wrench to something that is working. C M Automotive has offered to troubleshoot my manifold assy, so I may take advantage of that. I'm convinced that there is something amiss with the exhaust port/selinoid or associated wiring/connectors, or perhaps a missing internal part of some sort.

I did find somthing interesting as I tore apart the hubs. I think that the mechanic that worked on my particular deuce at the National Guard Motor Pool (no offense to any military mechanics) was not the highest trained individual. I did not know anything about these trucks, but I did know that these hubs had been taken apart and not reassembled correctly. So beware of that possibility.

Finally, I could use any advice from others that may have ideas concerning these issues. THX, Bob

LOL, mine "honks" from time to time. It's really annoying. A few months ago, I had decided I was going to drive the A3 to work after letting it sit for about a week. I have to be at my desk at 7:00am, and I live 50 miles away, so it's 5:30am. I come downstairs, put my boots on, and head out to warm up the truck. I start it, wait for it to air up, and went back inside. While getting my things together, the pizza I ate the night before reared it's ugly head....... and it was time to go take care of business. "Thank god" I thought while sitting on the toilet, "It would suck to have to take a crap this bad while driving the deuce......deuce....hahaha......"

Well, I guess I hadn't turned the CTIS off properly when I shut the truck down the last time, because while I was enjoying my morning poop, I hear "HUMMMMMMmmmmmmmmHOOOOONNNNKKKkkkkkkkkHHHHHUUUUURRRRrrrrrrrrr"

I knew what it was, and I also knew that if I was hearing it inside my downstairs bathroom (interior room in the center of the house) all my neighbors were hearing it as well.

"HUMMMMMMmmmmmmmmHOOOOONNNNKKKkkkkkkkkHHHHHUUUUURRRRrrrrrrrrr" it does it again. "Crap" I thought "I need to finish up NOW!" But Nooo, that wasn't going to happen; I had pulled the plug in the dike and all the evil behind it was flowing with vigor.

"HUMMMMMMmmmmmmmmHOOOOONNNNKKKkkkkkkkkHHHHHUUUUURRRRrrrrrrrrr"
"HUMMMMMMmmmmmmmmHOOOOONNNNKKKkkkkkkkkHHHHHUUUUURRRRrrrrrrrrr"
"HUMMMMMMmmmmmmmmHOOOOONNNNKKKkkkkkkkkHHHHHUUUUURRRRrrrrrrrrr"

My phone rings with a text message, it's my wife upstairs. "Are you planning on taking your elephant to work today? Or did you take up the Tuba without telling me?" "SHUT UP" I replied.

"HUMMMMMMmmmmmmmmHOOOOONNNNKKKkkkkkkkkHHHHHUUUUURRRRrrrrrrrrr"

Eventually I finished my business and sprinted out the door to shut the truck up. I was fully expecting someone to be out there beating on the door with a hammer, but I guess it was too cold for anyone to venture out.

Needless to say, I always make sure the CTIS is off before I get out of the truck, and after I start it in the morning.

 

[mktopside]

My unit is now working properly after replacing some pieces parts, but the problem I am having is the air dryer unit. I replaced the filter in the dryer but it is still venting too often and when it vents the CTIS purges and goes back to zero. Due to the rapid purging I can actually lose pressure when it is supposed to fill.

To get my system to work one must be on the highway and not stop for anything until the tires are up. Each stoplight takes about 2 psi out of the system.

Thanks for the info! It is great to get a better understanding of the system.

Sure you don't have an air leak somewhere?

Mine was doing the same thing, as I believe it is supposed to when it senses a drop in air pressure. After I patched up some small, but significant air leaks, my dryer stopped venting every 15 seconds.

 

[glcaines]

LOL, mine "honks" from time to time. QUOTE]

 

[AceHigh]

Mike, I read your post aloud to my wife- she loved my reading about your honks. Too funny!

 

[jaymcb]

While this is more operation than theory, does anyone with an A3 and CTIS find that the tires only inflate to a certain point when the truck sits at idle? Unless mine is set above the 'use CTIS at 1300RPM' engine speed, my tires do not inflate over 28PSI. (I have 1 tire with a slow leak).

Once the truck is driven, the pressure comes up to 43-44PSI

 

[Rustygears]

The volume of air required to inflate 6 super single tires simultaneously is MASSIVE! The little air compressor on a Cat 3116 doesn't have a lot of capacity at idle. 1300 RPM is almost 3 times more output than at idle. It takes a large volume of air to raise the pressure and the CTIS will actually inhibit when the air pressure of the truck supply drops below 50 PSI. This can happen if CTIS is activated at engine idle and the tires are all low.

Remember that all 6 tires (assuming each tire is above the 20psi CTIS threshold) inflate at the same time. There is no inflation by wheel or axle. They will all be connected together and equalize to a common pressure controlled by the CTIS. The only exception is the case where there is a broken line or a tire that is blown out. When the wheel valve detects deflation rate exceeding a threshold, the wheel valve will pop shut to isolate the tire (for protection). This is also the way CTIS shuts off. It always vents the manifold and lines to cause the wheel valves to close. CTIS deflation occurs at a slow rate to avoid shutting the wheel valves.

 

[motomacguyver]

As the original poster, it’s been awhile for me, but thanks for all the replies. I now have a much greater understanding of the system. In my particular case, I believe that two of my wheel valves are not functioning correctly, as air escapes from the little orange plug on the wheel valve until I block it with my finger. Then the valve seems to shut. I did find some rebuild kits on *-bay but haven't messed with it lately. I did send two valves to CM auto, and they kind of dropped the ball on them. They sent them back after several contacts with them, and the valves act the exact same way as they did before I sent them in. In CM auto's defense, people like me have to be a lot more of a PITA then any profit.

On a more of a "root cause of the problems" aspect; I suspect that the surface finish of the areas that the quad seals touch/ride/rub might be the issue. At work, as a machinist, any areas that have a rubber seal surface have a surface finish callout of 10-20 RMS. That is a finely GROUND, not machined on a lathe, smoooooooth finish, not a "mirror" but certainly not enough to even perceptively feel with your fingernail being dragged (drug?) perpendicular to the surface finish. So, next time I have my hubs apart I will check these areas. Also if you’re in your hubs make sure the cork gasket is in the keyway slot. Cut a wedge of cork material - I bought a thick valve cover gasket for a GM V8 - and cut some wedges out of it. Then coat in RTV and lightly tap the wedge in to the keyway slot and then the lock washer goes on. Search axel seals and you will find a great post on this for the A2’s but it applies to the A3’s as well.

 

[camoyj7]

Great thread! I've been wanting to get my ctis working for awhile now. Anyone post their part numbers for seals and other parts in the ctis or start a ctis parts thread yet?

 

[glcaines]

The wheel valves are actually very simple to take apart and clean. I've now done two of them and didn't have a kit. The gaskets were still good and didn't leak when re-assembled. I cleaned everything with mineral spirits and then washed everything with hot soapy water, followed by drying with compressed air to make sure I got all of the water out.