Tachometer doesn't work! :-(

[Eyvind Spangen]

I have done some measurements on my '90 200TQ. All ignition components
and all sensors measured ok, plugs were OK. It starts relatively easy
when it's warm, but in cold weather (below zero C), it's hard, almost
impossible, and in addition, the tachometer doesn't work. It started
easy down to -35 (never tried lower) before, so something is wrong.
Timing is OK, timing belt had _not_ jumped. In addition, the
tachometer doesn't work.

Someone here said distributor hall sensor, how do I test this better
than the method in the Bentley? Does this provide the tachometer
signal?

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Regards,
ES