That trailer is not worth your time. The kink in the right side rail in the picture would stop me from buying it. Also in another picture near...
I've seen a carbon plug in the line from the compressor to the tank keep one from building air. If the compressor is kicking out at 80 lbs, check...
I contacted Ryder about a truck they had listed within the last 2 months. I asked for a copy of the service records of the truck and was denied....
Check the exhaust ports of the foot valve and relay valves near the axles.