I have been having more and more frequent hot start problems on my 1990 740 GL (16 valve, B234F engine, 220K+ miles). Car will now not start today, after morning use, even after a much-prolonged cool-off (I'll check again in the morning). I've checked out the usual suspects following the FAQ advice, and I am now down to the RPM sensor. The engine end has the outer black insulation rotted off, but the wires underneath seem intact. Still, it does seem it needs to be replaced - but is it the cause of my current no-start status?

Testing the sensor/cable: I undid the cable at the firewall, but left it attached to the bell housing. Checking the three contacts on the RPM sensor cable coming from the engine, between one side and the center blade I get about 160 Ohms resistance; between the center blade and the other blade, I got no resistance or continuity.

Hmmm. Bad sensor/cable? Trip to the dealer to pick up a replacement? I've read the FAQ about cautions on doing this gently?

Advice would be appreciated. Many thanks.
Brian