CTIS, how can wheel valve decide?

[Farnorth]

I'm puzzled how my M923a2 wheel valve assemblies can allow deflation to run in sand mode, yet protect the tire from deflation when a supply line to the axle is removed or damaged?
i have an axle seal that is leaking air, so I removed the line going to that particular wheel, at the axle. I capped the line, and just put a rubber dust plug in the hole where it was. Yet I can inflate the tire with an air hose, and no air comes out the axle where the line came was removed.
Does the wheel valve need to have some pressure on the supply side to allow air out?

 

[camoyj7]

If you have a tire going flat remove hose going to valve stem and put a Schrader valve in. Refill tire if it goes flat it's most likely the o ring between the two piece wheel. Also check the small o ring in the hose that goes on the valve stem.

 

[Suprman]

Its all mechanical. The wheel valve has a flapper and spring. The valve can be held open with around 18psi to allow the system to dump pressure. Down to 18psi at least. Fill pressure opens the valve and forces air in until tire pressure and incoming air pressure equalize. A bad hub seal or large air leak can fool the valve by only around the 18psi reaching the valve since a significant amount of intended fill air is escaping somewhere.

 

[Plugugly]

How long does the CTIS put air to a tire before it gives up? I've got a sloooow leak on one tire, I chased the wheel valve and o rings in the CTIS to where that doesn't leak. It will still leak down to about 40psi in a week then just stay there. If I air that one tire up, the CTIS has no issues. Sometimes, if I don't air it up, the CTIS seems to give up and give me the five flashing. Sometimes not. My truck is putting out good air, 120-130 on both gauges.

I'm almost positive it's the wheel o-ring giving me the issue, but I've not really worried about getting it fixed since it's a minor inconvenience.

 

[Suprman]

With a full tire, and when you know the truck will be sitting for some time, take off the feed line from the hub to the wheel valve. Leave the line from the valve to valve stem on. Get a good plastic bag scrunch it down over the wheel valve and rubber band it tight over the valve stem line. If the valve is leaking the bag will inflate over time. You can check the lines and rim with windex looking for air bubbles.
Will

 

[Plugugly]

I did the soapy water and found a wheel valve leak, and a stem o-ring leak and fixed those already. That's why I think it's the rim o-ring. I might try the valve in a bag thing if it gets worse, thanks for the tip. I guess to my original question I should just time it with a stop watch, I can hear the air flowing after the system hits 120psi, it must have some set parameter to flow air before it shuts down.

 

[Farnorth]

It looks like I have a leaky hub seal. Does anyone have a part number for this seal?