Bigboy down again,M923 won't build air past 59psi

[Getagun]

So flipping the plunger fixed your ability to air up past 59psi ??

 

[Getagun]

So flipping the plunger fixed your ability to air up past 59psi ??

i just replaced the check valve on the vent tank cause it was leaking all the air back thru the compressor into the intake manifold.
$20 dollar part and fixed my problem.

 

[tbar123]

Getagun; Replacing the valve in front of the transfer case (post 56) resolved the airing up problem. Then flipping the piston fixed the air leaking into the stack after I flipped the dash switch.

 

[Getagun]

Well I checked both transfer case valve and solenoid and no leaks there
I pressurized the system all the way up to 150 and the system all works properly.
Ctis works
governor works

current issue won't build pressure past 59 or so
I've bypassed the dryer and replaced governor

heres where it's weird.
I can charge the air system and drive
system builds pressure just fine as long as I'm rolling and everything works . At 0mph no pressure build up at all no matter what rpm
shutting both valves on wet tank doesn't make a difference at 0 mph
nothing leaking at all. Did the soapy water trick everywhere. No leaking into intake tube

possible uploaded valve or compressor. The whole has to be moving thing has got me confused.

 

[Getagun]

Getagun; Replacing the valve in front of the transfer case (post 56) resolved the airing up problem. Then flipping the piston fixed the air leaking into the stack after I flipped the dash switch.

Also what does that valve do. I played with it and seems to do the same thing the dash valve does.

The silver button on top of the transfer case hi low seems to produce a little air low pressure leak of some sort when pressed not sure what exactly it does either. You'ld think if it was air related there would be move pressure

 

[tbar123]

The valve in front of the transfer case locks the front axle in when the transfer case it switched to low gear. Without the dash switch being engaged. I would suggest against driving your truck (unless your on private property) until you get this issue resolved. You could have a catastrophic system failure which could end very badly.
sounds like your truck is an A2? When you aired the truck up did you walk around and under trying to hear air leaking? PM sent.

 

[Thomas_G]

I had this same type of issue on a M939. I took the air dryer apart, cleaned and resealed and it worked good after that.

 

[The HUlk]

possible uploaded valve or compressor. The whole has to be moving thing has got me confused.

When it is not building pressure, remove the large air line(output) at the compressor unloader valve. Is any air pressure being produced? If no then remove the small control air line at the compressor unloader valve. Is any air pressure being produced now? If not then the unloader valve is probly stuck or worse.