Whoa boy, here's another example of this highly frustrating experience....
OldnDecrepit;7646 wroteSo it seems that the starter is the culprit - yes?
Well... maybe. In my cases of Starter Motor Tango, it works fine when it gets enough juice. Or it's cool. But give it some heat or let the voltage drop a wee bit from having the radio on, and it won't kick.
Y'know... I'm starting to suspect the wiring from alternator, to battery, to engine, isn't up to the task. Neither is the engine ground, which is found running from the battery to the chassis, and then from the chassis to a bolt on the RH front engine mount
Funny thing is, I've recently parted a 940 NA in which somebody has run a second and far thicker positive battery cable directly from the battery to the starter, but routing the new cable around the RH suspension tower, across the firewall from RH to left, and then down to the starter motor. The usual route for the positive cable is under the RH side of the engine, along the front crossmember, and over the LH engine mount to the starter motor.
This same person also added a significantly bigger earth cable from chassis to engine.
Why all the logorrhea? Just that it may not be the starter motor at fault, but rather a failure by age of the inadequate OE battery and earth wiring.
How difficult is it to remove the starter on this model?
About the same as a late 240 since you ask... but!
The usual trick with 240s and the like is to just drop the tranny crossmember a couple of inches so that you can get to the upper bolt on the starter motor.... Not with these! The head mounted distributor and the firewall can be damaged if you drop the transmission without a little prep. So you have the choice of removing the dizzy and doing the trans crossmember trick, or using a socket extension with a CV-like joint on it to get to that elusive top starter motor bolt. IIRC, 16V engines had the lightweight wizz-bang starter which has self-tapped holes on the starter motor flange, so the bolts have to be removed from the bellhousing side and withdrawn in a southerly direction.
Ratchet spanners make R&R of the head-mounted dizzy a lot less painful and save much time.