I should have said "MPG" ignition. That's the more common one for the Chrysler developed system used on some '82s and the '83 — '88 240s. I'm surprised that your '85 still has the Chrysler distributor cap. I thought that most were converted to Bosch by then.
The MPG Ignition Control Unit (ICU) should be on the right side, near the washer reservoir. Here are 2 basic tests. There are also some additional voltage tests, if needed.
MPG Ignition tests
A - Hall/ICU Quick Check
1) Pull coil wire, attach/adapt to spare (grounded) sparkplug
2) Remove distributor cap
3) Rotate engine till the Hall Switch is centered in a Vane "window".
4) Turn Key ON
5) Pass a feeler gauge blade (or similar) through the Hall Switch (simulating the Vane)
•) If the Hall Switch and ICU are OK, you should get a spark and fuel pumps should run for a second.
•) Repeat step 5 as needed to verify spark and pumps.
•) If no spark, test ICU function below (eliminating Hall Switch)
B - ICU switching function
1) Key OFF. (Coil wire and spare plug still set up as in Step 1 above)
2) Remove the 3-pin plug from distributor body
3) Insert a jumper from pin B (Yellow wire) to pin C (Black wire)
(When jumper is REMOVED (with Key ON), the plug should spark, and the fuel pumps should run briefly.)
4) Turn Ignition ON. Check for spark and pumps as jumper is removed.
•) If Spark & Pumps now, suspect Hall Switch or wiring problem
•) If no Spark, suspect ICU or wiring problem
Bear with me if this isn't perfect. I don't have an example on hand, haven't seen one for some time, and had to pull this from two sources.
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Bruce Young, '93 940-NA (current), '80 GLE V8 (Sold), '85 244 ti, '83 245t '76 244 (lasted only 255,000Km), 73 142 (98Km) '71 144 (track modified--crusher bound) New 144 from '67 to '78, Used '62 122 from '63 to '67
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