Re: Flywheel Sensor Replacement UPDATE
Interesting! Lots of useful points there. Do you think, if the resistance was correct, that it could have been just the air gap that was stopping your old flywheel sensor from functioning? Often (though probably not in your case) it's just the connector which has a hard life hanging around under the coolant tank, above the gearbox.
Thanks for posting this info... I'm fairly certain it applies to the Mk1 as well...
The Haynes manual does quite a good job of enunciating the various sensors... I think the two sensors (crank angle and speed sensor) are both for the ignition system? One sets the timing (crank angle, near crankshaft pulley) while the other sets the advance (engine RPM counted from flywheel teeth).
While it would theoretically be possible to get the engine RPM from the crank angle sensor, I suspect it may not be accurate enough. And as for the flywheel sensor, unless the flywheel had an intentional missing tooth, there would be no crank-angle sensing possible!
Another possibility is that the two sensors are necessary because the fuel injection and ignition are two separate ECUs (unlike, say, Bosch Motronic which combines them). In the Uno Turbo, the ignition is Magneti-Marelli while the injection is Bosch. But, I don't think the injection system actually has any engine speed input at all? I wonder how it 'knows' how often to spray fuel in? (The quantity of fuel depends mainly on the airflow meter and the coolant temperature sensor - but I don't know what controls the injection timing.)
Cheers,
-Alex