
Did you not try to clean the old sensor first?
I would expect that as the engine had been stood for a while your flywheel would have got rust on it. I get this a lot with clios that have been stood for a while. They will start and run no problem for a few weeks, Then as the magnetic crank case sensor picks up the flakey rust from the flywheel the sensor gets clogged. 99 times out of 100 when i remove the sensor its covered in crud just like an A.B.S. A gentle emery paper clean up nearly always does the job for me.
I know its a bit late now for you Trev and i hope im not teaching you to suck eggs? Just thought it a point worth noting for everybody this..