Yet another CTIS issue

[Five.slow]

Long time lurker, first time poster.
In my shop we got a 1078a1 with the following CTIS issue: 5 flashing lights. After starting I get flashing highway light. As soon as the air builds up and purges from air drier the 5 flashing lights start. I hear the CTIS manifold try to supply air, at the same time I hear air escape at the rear of the vehicle that’s when CTIS shuts off with the 5 lights. Iv jumped pins at the CTIS wire harness to open the manifold to supply air. When I do that air dumps out of the rear quick release valve.

why is this happening?It’s got a new manifold and new quick release valve.

 

[Suprman]

You have a leak somewhere. Broken fitting maybe a hole in a hose.

 

[Five.slow]

You have a leak somewhere. Broken fitting maybe a hole in a hose.

iv worked on these for 20yrs but usually we just ignore CTIS lol. Will a leaky rear CTIS hub seal cause the air to just dump out of the rear quick release valve? We are doing seals just because we got them. We have no other leaks at all. Iv been all over this truck.

 

[Suprman]

It could. Do you have hub oil in your banjo bolts. You can take each line to hub off the qr valves and individually pressurize with a compressor look for leaks. Ive seen alot of the elbow fittings at the hub input crack. Old air lines get small holes.

 

[Five.slow]

It could. Do you have hub oil in your banjo bolts. You can take each line to hub off the qr valves and individually pressurize with a compressor look for leaks. Ive seen alot of the elbow fittings at the hub input crack. Old air lines get small holes.

no oil coming into the wheel valves. Just opened all of those and cleaned them up. Waiting on the other guy to put hub seals in and we will see what happens.

 

[Five.slow]

New manifold, new quick release valve, new CTIS seals, good wheel valves and no leaks. Still blowing air out the rear quick release valve.

 

[Ronmar]

The only way air can dump out of the dump valve vent is if it comes from the tires. If it dumps as soon as the manifold applies air to the system, then I would say the dump valve is installed backwards. IE: truck side line from the manifold connected to the output port and the lines to the wheels connected to the input port.

the QR/dump valve is a remote pressure reg. Whatever pressure you put on the input port it mimics on the output port. Put 100 in, you get 100 out, drop the 100 to 20, the output side will dump 80 psi out the vent port till output again = input at 20 psi…

 

[Five.slow]

The only way air can dump out of the dump valve vent is if it comes from the tires. If it dumps as soon as the manifold applies air to the system, then I would say the dump valve is installed backwards. IE: truck side line from the manifold connected to the output port and the lines to the wheels connected to the input port.

the QR/dump valve is a remote pressure reg. Whatever pressure you put on the input port it mimics on the output port. Put 100 in, you get 100 out, drop the 100 to 20, the output side will dump 80 psi out the vent port till output again = input at 20 psi…

you cant swap lines on the valve. The supply is a completely different fitting type. This is annoying now lol

 

[Ronmar]

you cant swap lines on the valve. The supply is a completely different fitting type. This is annoying now lol

Well it doesnt change how the valve works. In normal ops, the vent port can only expel air returning from the outlet port which should be connected to the tires.

Another possibility is you have a severely kinked or crimped line to the input port of the valve. This allows enough flow thru the dump valve to open the wheel valves, and then tire air being at a greater pressure flows back to the dump and exits thru the exhaust horn.

Are you sure its coming out the vent/dump horn on the valve and not from something like a split line on the input?. If so, its either plumbed wrong or defective, or its like i described above...

 

[Five.slow]

Well it doesnt change how the valve works. In normal ops, the vent port can only expel air returning from the outlet port which should be connected to the tires.

Another possibility is you have a severely kinked or crimped line to the input port of the valve. This allows enough flow thru the dump valve to open the wheel valves, and then tire air being at a greater pressure flows back to the dump and exits thru the exhaust horn.

Are you sure its coming out the vent/dump horn on the valve and not from something like a split line on the input?. If so, its either plumbed wrong or defective, or its like i described above...

100% coming from the bottom of the valve. I donno the history of this truck. I feel like there is a line somewhere not connected in the correct stop. Issue is I don’t have a good schematic.

 

[Ronmar]

100% coming from the bottom of the valve. I donno the history of this truck. I feel like there is a line somewhere not connected in the correct stop. Issue is I don’t have a good schematic.

Well the CTIS plumbing is pretty simple. The single output from the pressure control unit manifold goes to a T inside the frame, by the rear of the trans, passenger side. One port goes to the front axle dump valve input port, located a foot forward to the right of the transmission. Crawl in under the fuel tank and look up, cant miss it...

The other port on the T goes to the rear axle dump valve(or valves on a 6x) located over/behind the axle.

 

[Five.slow]

Found the issue. A line was “replaced” once. They spliced into the supply line and when they did they used a small inside diameter hydraulic union fitting. I put an air line union on it with proper inside diameter and it fixed the issue.

thanks for the help guys now I understand how this system works!!

 

[coachgeo]

Found the issue. A line was “replaced” once. They spliced into the supply line and when they did they used a small inside diameter hydraulic union fitting. I put an air line union on it with proper inside diameter and it fixed the issue.

thanks for the help guys now I understand how this system works!!

ahhhhhhh..... so like Ronmars description of a pinched line.. that repair that would in many instances be fine/but not here...... ended up changing the pressure and causing valve to dump.

 

[Ronmar]

When the outlet is greater than the inlet, and it shifts to dump, it also feeds back a little air from outlet to inlet port. If the controller held the PCU in the pressure test state longer(Control valve closed), the pressure on the dump inlet would have steadilly increased untill it eventually equalled the outlet pressure and stopped dumping.

This takes about 20 seconds. The CTIS controller faults and aborts the stable pressure test long before this though.

I think you can see it(and hear it) in one of my manual CTIS videos on utube. As the inlet pressure rises, the dump steadly reduces the venting untill the pressures are equal...

 

[Five.slow]

ahhhhhhh..... so like Ronmars description of a pinched line.. that repair that would in many instances be fine/but not here...... ended up changing the pressure and causing valve to dump.

Exactly. Enough pressure to make rear wanna dump but the controller is calling to air up so it shut down.

 

[Five.slow]

When the outlet is greater than the inlet, and it shifts to dump, it also feeds back a little air from outlet to inlet port. If the controller held the PCU in the pressure test state longer(Control valve closed), the pressure on the dump inlet would have steadilly increased untill it eventually equalled the outlet pressure and stopped dumping.

This takes about 20 seconds. The CTIS controller faults and aborts the stable pressure test long before this though.

I think you can see it(and hear it) in one of my manual CTIS videos on utube. As the inlet pressure rises, the dump steadly reduces the venting untill the pressures are equal...

Gotcha. Thanks for the info.

 

[Ronmar]

Yea CTIS isn’t very smart. It is expecting things to happen a certain way in a certain timeframe, and if it doesn’t see it, it faults. It probably first starts with a sensor test to see if the pressure sensor on the PCU is reading atmospheric pressure. Then when the air system fills, It performs a pressure test when it sees the wet tank switch close ~117PSI. It closes control(control solenoid) and gives a brief shot of wet tank air to the manifold(supply solenoid). This shot should pressurize the lines from PCU thru the dump valves above tire pressure, which the dumps pass along to the wheels. As soon as the wheel valves go over ~5PSI on the truck side of the valve, they open and connect the tires to the system.

since the input side should be a little higher than the dumps, they shouldn't dump, and the PCU manifold should pretty quickly stabilize at tire pressure. If the controller doesnt see stable pressure after a very short while, it aborts the test, opens control which causes a brief dump and quickly closes the wheel valves when they go below 5PSI on the truck side. Then it starts flashing. That is why it typically faults if you have one tire lower than the other, the pressure cannot stabilize in the time allowed by the controller. Which is what yours was doing, couldn't get a stable pressure in the time allowed…