Fast Idles solenoid valve question

[Cary and Don]

Our fast idle solenoid valve on the engine bulkhead started leaking out the exhaust port.  Seemed like an easy fix.  This did start suddenly.  Put on a new valve and once the air pressure gets close to operating pressure,  it blows air too until all the air pressure is gone.  It did seem fine until the air pressure built up.  The wiring was not on the connections, so the fast idle switch could not have been on. We do have a jake brake buffer switch. Could the push rod valve on the governor be causing this or is it something else?  Doesn't seem possible that two valves, one new, could have the same problem.

Don and Cary
1973 05 Eagle
1966 GMC 4107
Neoplan AN340 

[bevans6]

Try disconnecting the air line from the Skinner valve to the fast idle and throttle lock cylinders, same line should go to both, so you can see what is happening without putting the engine in fast idle all the time.  That valve is usually supplied from the accessory air system, so behind the  pressure protection valve so no air should be getting to it until system pressure is past 60 PSI.  The valve is normally closed, no air delivered to the fast idle cylinder, when there is no current to the solenoid, open when current is on, ie. when the fast idle switch is on.  Try building air pressure and see what the valve does with the electrical line disconnected, it should not pass any air.  It should only pass air when there is current at the electrical connection.  On my bus, there are separate ground leads that connect to the electrical plug, make sure the ground are good or  the solenoid inside the valve may not operate fully.    There are three air ports on the valve, and each can be either in, out or exhaust depending on the application for the valve, so double check that your lines are on the right ports.  I don't think that anything on the governor could be causing air to leak at the valve. 

Just my thoughts...

Brian