Air pressure trouble

[hogi6123]

I took my bus out for a ride.  It was working fine.  I shut it off, 20 mi from home, now it starts, pressure is holding but doesn't build.  No air leak sounds from underneath.  8v92t manual.  Any suggestions?

[buswarrior]

Agitate with vigour, both brake systems, parking and service.

Something hopefully stuck half way between seated and unseated

Happy coaching!
Buswarrior

[chessie4905]

Try tapping air compressor governor.

[hogi6123]

I tried draining all air tanks and restarting the engine.  And tapped on the governor best I could.  I walked to the nearest hardware store and bought a small 110vac compressor.  Now pumping up...

I will have to service my governor and compressor before my next trip.

[hogi6123]

The compressor I got will take several hours    If my wife had stayed home she could have brought me a bigger one.

[hogi6123]

The little compressor couldn't handle the whole bus, so after a loong time trying, to actually get out of there, I moved the compressor to the emergency brake fill and pumped that to 120 psi.  The parking brake released (one full application of service brakes needed) and then I drove the bus home without using the brakes, so I wouldn't get stuck somewhere in the middle of the road.   Sigh... my first disabled bus experience. 

[chessie4905]

Just curious. Was it this one?
https://www.harborfreight.com/1-gallon-135-psi-ultra-quiet-hand-carry-jobsite-air-compressor-64592.html

[dtcerrato]

.7 SCFM @ 90 psi is way too small for just about anything in a real fancy looking unit. Our vintage electric aux. on board air compressor is 6.4 SCFM @ 90 psi. Enough to air a totally empty bus up in 10 minutes..

[luvrbus]

`Takes a good size compressor to pump as much air the the 10 to 14 CFM engine compressor does ,in most cases you can disconnect the 1/4 inch control line from the governor and the compressor will pump up

[hogi6123]

It was this one, 0.5 scfm at 90 psi.  And LOUD!

https://www.acehardware.com/departments/tools/air-compressors-and-tools/air-compressors/1000941

At 65 psi, valves between tanks open, and some small leaks start that eventually stop around 100 psi (wipers).  So the compressor got to 65 psi but couldn't make any headway past that.

[chessie4905]

wasnt recommending that one. Way too small for a coach. That thing is good for car and truck tires if you need a small one. Fortunately, he got by this time with the one he bought enough to move it.

[hogi6123]

I finally was able to dedicate some time to this issue.  Looking at the manual, I saw 4 main possibilities:

1. Intake is completely plugged
2. Outlet is completely plugged
3. Unloader is stuck in unload position
4. Some kind of catastrophic internal failure

I checked 1,2,4, and then took the compressor out. The unloader plungers in the compressor were stuck in the 'unload' position.  So a little cleaning, new gaskets, and a very tough time getting it bolted back onto the engine and it'll be good to go again.