Engine and compressor run for 15 seconds then dies

I have a 1965 towable oil flooded rotary screw compressor. Kargard industries. I know they are out of business now. The problem I am having is: The engin will start and run the compressor only with the discharge open. If i close the discharge valve to have the compressor idel down it stays at full speed still and stalls out. Happens after about 10 to 15 seconds. Also the engine won't run if taken off of half chock. I know that could be the carberator. I saw that there is a spring on the back of the regulator valve and also that conects to the throttle linkage. I can manually move the throttle but engine will not rev up or down. Compressor blows good air when it runs for a little bit. Also engine will run rough and die after a short time of compressor running hard. Maybe about 5 minutes. Any ideas?