Rolair 4090hk

4 years 4 weeks ago #1882 by Twoodman66
Rolair 4090hk was created by Twoodman66
Was given the 4090hk17 as a tip..
Compressor fires right up but will not stay running. Did complete tune up and new unloaded valve
Not sure where to turn next. Was going to pull the belt to see if it would run without a load on it. Pump builds pressure regulator seems to work.

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4 years 3 weeks ago #1885 by MTR-Admin
Replied by MTR-Admin on topic Rolair 4090hk
Thanks for the post!

Since you replaced the Pilot/Unloader Valve already we'll rule that out, as well as the pump as you mentioned it's been rebuilt.

Have you replaced the Throttle/Idle Control Assy that connects the Unloader Valve to the engine's governor/throttle arm? It may be that the engine speed is too low...are your RPM's near 3,400 when the unit is pressurizing? I believe that is the correct RPM while the unit is "loaded" and running.

If your Throttle/Idle Control is in good shape and your engine RPM where it's supposed to be, I'd wager the Drive Belt is too tight or too loose. If you press down on the center point of the Belt there should be 1/2" deflection.

But yes, I would take belt off and run it with no load; afterwards, reinstall the Belt and remove the copper Discharge Tube from the Pump to the Tank to see if it runs without it.


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