The Volvo/Chrysler ignition (late '81 thru '88 240s) is usually very reliable. My faughter had a failure once that was simple corrosion at the coil Primary terminals.

The Bentley manual has procedures for testing the Hall Effect sensor in the distributor (basic timing pulse) and the Ignition CU itself.

Here are my excerpted versions of those 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
(step #4) 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

--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.