Hi Bunklash. You
Found it!
Turns out SOMEBODY

didn't get the exhaust valve positioned properly after they had the head off. Fixed that, now it works like a champ

.
I have the same situation. A Dewalt compressor given to me. However, I'm not sure what you mean by the exhaust valve positioned properly. Do I have to take the motor apart? I have no problem do it, as long as I know what to look for. I looked at the Dewalt compressor diagram, but can't find the exhaust valve. If you could help, it would be appreciated. Thanks