M939a2 ctis

[Smckerigan]

Morning, I have been working on my M939A2 Ctis system for a couple of months since I got it back in September . I have removed all the valve stem cores fixed leaks from the wheel valve hoses and some other small leaks. I have the system working somewhat as it will start to work as the tanks reach 120psi and will pump up one of the low tires on the mid left tire. After 20 minutes or so the only mode I can acheve is the sand setting and it will stay solid but it will never get a solid light on there xcountry or the hwy mode. I have checked and replaced all the PCU orings and did the resistance test on the three solenoid so and they are all at 47. So I reall don't know where to go now now. Thanks sean

 

[MtnSnow]

My first guess would be that you have a QRV (Quick Release Valve) that is leaking or a Axle seal

 

[74M35A2]

If you are trying to reach target pressures at idle, the system can time-out if leaks in the air tank system are prevalent or you air governor threshold is set too low. Raise idle to 1500rpm with the cable or try it while driving.

 

[Smckerigan]

Thanks for the help! I did raise the governer from around 120 up to 130 psi and it was but still didn't help, I'm looking more at the QRVs. I'm just going to replace the three QRV valves because I did notice air coming out of the rear valve when it was filling the system but I thought it was just releasing air for the other axles to equilize the pressure but I didn't think they were working correctly .