Secondary air tank filling, primary not filling, valve problem?

That dryer (ADIP?) has pressure protection valves. IIRC, primary should raise to 92 or 93 PSI before sending air to secondary.

I would R&R the assembly at it's age.

 

I'll second what Big Road Skateboard says in post #11 to rebuild or replace the dryer. Re-Connect the supply and governor line but leave the green one disconnected. Run the truck and see if there is air coming out. If not problem is in dryer. If so re-connect and go to the other end of green line at the tank, disconnect and run truck to see if air is coming out. If air is coming out there then I would remove the fitting, you could connect the air line to the removed fitting and see if air comes out with truck running. It does not look like there is a check valve going into the tank, not one like this.

 

Small black? Governor signal.

Scratch that, i see your pic. That'll be unloader signal from the governor to air compressor

 

Aren't the Cascadia the ones with the split wet/primary with the check valve on the internal wall of the tank? Or am I remembering something different? Those you have a fitting on the end of the tank to remove to access the check valve with a long extension & socket.

 

May not be your exact dryer but yes they have a check valve at the discharge port.