I've been having trouble diagnosing a problem with my '87 240. Stumbling on acceleration, bad idle, slow start. (Further details if you search for Duggernaut) Its been suggested that its a bad AMM. I've tried to determine it is not anything else and have done lots of maintenance items to avoid getting an AMM. (Flame trap, clean throttle body, IAC, okay fule pressure regulator)etc.) The car ran well for ten minutes after cleaning TB and then died on me. It seems to me that the starter failed (No cranking)and that it is an unrelated problem. I figured I should replace the starter and then diagnose the original problem. It occurs to me now that maybe they are related. Maybe the AMM finally completely failed and will not let the car start. Is this possible? I tried to take readings of the AMM. THe only reliable reading I could get was for the test from the 2 and 4 relays. They should be between .5 and .9 (Can't remember exactly now)and mine read at .3
Is it possible that a poor acceleration/ stalling and a no start are related problems? Would a bad AMM cause all of these symptoms?
Help is very much appreciated.

My impression is that the engine will run with the AMM disconnected (though poorly). So if car runs rough with and without AMM then probably something else.

A rough idle may be caused by a vacuum leak sucking in too much air. Check for holes in the intake hose after the AMM.

If your starter isn't turning the engine over, it could be a wiring/switch problem. Try shorting across the posts at the starter, thus bypassing the ignition circuit to see if the starter will turn over.
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1980 245 Canadian B21A with SU carb and M46 trans

I came across you question today while looking for earlier soltions to my problem posted yesterday on 2500 rpm idle. I had replaced real crank seal which necessitated removal of the starter. Upon reassembly and restart, the starter would not disengage. Same problem with coil wire pulled so engine would not start; after inition position activated the started continues to run (keys in hand)until the battery line is pulled. The old engine wiring harness weakness had surfaced and I had a 2 to 3 ohm circuit between the the two 16 gauge wires that connect to the solenoid on the starter. Ended up pulling the whole intake system out airbox to head to remove and repair the harness.

Perhaps you have disturbed an already damaged or broken wire in the harness and know the starter solenoid is not geting the juice.

Just a thought.