Shutoff valve at top of fuel filter stuck
 

Hi,

I just tried to turn my fuel shutoff valve (plastic knob located on top of fuel filter) in the case that I loose vacuum and the engine was to keep running.

It has an arrow (clockwise) for stop, but it is stuck tight. I even tried a pair of multigrips but given that the knob is plastic, something is going to break.

Has anyone ever had one of these get stuck or do they colapse maybe?

Thanks