Can't build air

ok I have a 97' KW t2000 with the 3406e. I have a problem building up my air it seems that every cold weekend I park and first go it takes forever to build up last weekend had to let it run for over an hour to get it up once I get it built up I can go all week never having a problem even after shutting off the truck for a few hrs. Warm weekends no problem at all building pressure.
I do hear a leak coming off the backside (3/8 whole threaded) of the Unloader ( I think that's what it is a round tube with a cap and under the cap a threaded rod with a 10mm nut) anyways this morning after a 10 hr break at the house so it was off I can't get the air to build above 60 PSI I plugged the hole for a couple and still would not build air unplugged still no change after an hour and a half no air I gave up shut it down.

Only two leaks I can find in the system is one the one on the unloader and the second it the primary low pressure valve till It get built up both quite once built up. neither seem to slow it down if truck unless its been off for several hours and is clod get above thirty and even though they act the same I build pressure right.

thanks up front for any suggestions
Tsavory

 

thanks just had a buddy stop by that was an o/o for years he said that the governor is stuck.
first time for everything all other air problems where an air-dryer that went bad and lost all air in the middle of the street fast and break chambers and air line leaks first time with something on the compressor.
thanks for your input.
Tsavory

 

I do at least three times a week.

 

Update it was the governor went got a new one replaced and back on the road lost my original load but hey got me on something with in minutes of letting them know I was back up and able to go love it hardly ever any waiting for a load.