M1083 CTIS issue

[gauntcharlie]

Current situation: My motor pool has a M1083AP2 that loses all air in the front tires when the CTIS ECU is plugged in. The truck is a lateral transfer from Fort Bragg. My maintainers have changed out the air dryer, purge valves, CTIS filters in the tires, air hoses and tires themselves. The ECU is brand new and Pneumatic switches have been replaced. They have used the TM troubleshooting tree and procedures with no luck. Any ideas as to what else to look for? I always feel that it is something over looked and simple just looking for any suggestions.

 

[coachgeo]

CTIS Filters???? What year truck is it?

 

[Plasa]

Do you hear the PCU valves working? Maybe somone change wheel valves and put 70psi instead of 85psi wheel valves on the front axle?
Happen to me at beginning of my LMTV journey...

Christian

 

[Ronmar]

Both front wheels have one component in common, the front quick release/dump valve which is located between trans and fuel tank. The dump valve is a remote pressure regulator. Whatever the input pressure, the dump valve matches on the outlet(wheel side) by feeding air from inlet to outlet or dumping outlet side air thru it’s vent port till it matches the input side pressure.

To deflate tires you send air down the line thru the dump valve to open the wheel valves. Then you lower the dump inlet pressure to below that of the tire pressure, but still above the 7 or so PSI required to keep the wheel valve open. Since the inlet side is lower than the tire pressure, the air from the tires exits thru the dump valve Vent.

Whenever the system is done testing, it vents, which causes the dump valves to vent briefly(small honk) If the sliding core in the dump valve is not shifting cleanly, it could behave like it thinks it still has a small amount of input air, to which it matches the output side, deflating the tires down to that point...

 

[Suprman]

I wonder if someone swapped out the banjo bolts for regular bolts. Pull one out and see.

 

[Ronmar]

I wonder if someone swapped out the banjo bolts for regular bolts. Pull one out and see.

Yea, forgot about that weird one. that would cause a real slow deflate, a bad dump valve would deflate fast...