420 Icu
 

What exactly does the Ignition Control Unit Do? And would this cause missing at first,then not firing at all?

The ignition control unit controls ALL phases of SPARK control.

Processes the signal from crank sensor from an A/C wave into a square wave for the fuel pump & tachometer to operate.

Uses the signal from crank sensor to "turn the coil on/off".

Constantly adjusts the ignition timing for most power w/o detonation.

Failure of that part is VERY rare.. a "bone yard" replacement is the best way to find out if it is causing the problem.. Crank sensor failure is MUCH more likely.

200k service for 420SEL
 

Question for MB DOC: What does the 200k service include?

Rpm Sensor
 

Look up this on the search you will find repairs and problems associated with that item.I had to remove mine from a 420 sel for intermittent start and stalling.
The 420 I have been working on for 10 months now is in the last stage of repair and I have a great deal of info on problems and ending results, look up just-n-time post's Good luck and I will be glad to help if I can.JNT:wacko:

i completely agree with m.b. doc most likely cause of no spark is the pick up at the flywheel with single wire to ignition module on inner left fender.