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Author Topic: 4905 WILL NOT AIR UP  (Read 750 times)
5B Steve
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« on: December 08, 2012, 04:48:01 PM »


 Good evening,

   I am sending  this question out to anyone who knows anything about a GM 4905. Larry P bought one in the last

  several weeks, started it up today and it will not air up and he has no throttle. The bus has been setting for

 about 6 months and has what looks like a new compressor. The previous owner said it was new.  Larry mentioned

 it felt warm/hot to touch.   Any thoughts on this problem?

Steve
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Sam 4106
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« Reply #1 on: December 08, 2012, 05:13:31 PM »

If the bus is in a part of the country with freezing temperatures the air governor may have ice in it. Give the governor a few taps with a small hammer, that may allow it to build air. Or you can warm up the air governor with a propane torch, but be careful not to overheat it or melt any air lines.

Good luck, Sam
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
Ed Hackenbruch
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« Reply #2 on: December 08, 2012, 05:14:36 PM »

Check to see if the ping tank is plugged up. Smiley
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
chessie4905
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« Reply #3 on: December 08, 2012, 05:24:35 PM »

Since it has an air throttle, it won't respond till you have some pressure. It DID make air since he bought it??? Did the previous owner mention why it was replaced? (just in case it was changed to fix a problem and it didn't fix it, so your friend bought it? If it was working since he bought it, it probably a problem with moisture that changed to ice. Does the coach have a block heater with electricity available?
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GMC h8h 649#028
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5B Steve
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« Reply #4 on: December 08, 2012, 06:41:44 PM »

If the bus is in a part of the country with freezing temperatures the air governor may have ice in it. Give the governor a few taps with a small hammer, that may allow it to build air. Or you can warm up the air governor with a propane torch, but be careful not to overheat it or melt any air lines.

Good luck, Sam

  Hello Sam,   At this time Larry is in the London , KY area. Rain in the area no iceing. 

  Thanks for the reply.

  Steve 5B....
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5B Steve
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« Reply #5 on: December 08, 2012, 06:43:02 PM »

Check to see if the ping tank is plugged up. Smiley

  Ed, I'll pass that along, thanks.

  Steve 5B.....
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5B Steve
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« Reply #6 on: December 08, 2012, 06:52:57 PM »

Since it has an air throttle, it won't respond till you have some pressure. It DID make air since he bought it??? Did the previous owner mention why it was replaced? (just in case it was changed to fix a problem and it didn't fix it, so your friend bought it? If it was working since he bought it, it probably a problem with moisture that changed to ice. Does the coach have a block heater with electricity available?

 Chessie 4905.

  He was told it was replaced, however it has been sitting for about 6 months, weather that has anything to do with it I don't

  know.   When I get more info I'll pass it along! Thanks for the reply.

  Steve 5B......
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luvrbus
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« Reply #7 on: December 08, 2012, 07:01:07 PM »

Disconnect the 1/4 inch line going from the governor to the air drier if he has a drier that should start it pumping
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« Reply #8 on: December 08, 2012, 09:25:23 PM »

Well, you could freak out...

Or, for starters, advance the throttle by hand down the back in the engine room.

For my money, this old coach is leaking air someplace.

Run the engine hard and see what the air pressure does, and report back.

Bought a new to him coach and left it sitting for 6 months?

That's asking for trouble, and now he's got it.

happy coaching!
buswarrior
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Frozen North, Greater Toronto Area
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