On my 601 I have to push the lever all the way down and hold for a second or two.
If you replaced the O ring and the linkages were pulled out of position within the injection pump, the lever wouldn't function. Hopefully that isn't the case. When you did the O ring, did you pull the stop lever shaft out of the IP?
A halon or CO2 extinguisher would work, but just be damn sure you don't have an ABC dry powder extinguisher. That would destroy the engine instantly.
