Terex TS14B blower

Hey everyone! Just got a TS14b from an auction. Had some old Euclid S18s with 6110bs in them but never a little 471. The back engine won't shut off with the blower. You flip the lever and I can hear it close and motor slows down but chugs black smoke. It runs at a very low idle. Had to loosen fuel lines to get it off. Any ideas? Could it be a gasket in the box? Or do I need to go into it?

Terex TS14B blower