I have an '88 740GLE Wagon, non-turbo, with an electrical/ignition problem.
It orginal wouldn't ture over, just a heavy click. After doing the following I got it to crank:

1. Charged battery, only a year & half old
2. Replaced Positive (+) Battery Cable
3. Replaced Positive (+) Wire Feed Connectors at battery (sodered)
4. Cleaned and Reseated negative (-) battery cables and grounds to block and frame
5. Swapped out misc. relays with used, no response, replaced originals
6. Replaced Starter/Solenoid
7. Cleaned and INcreased tension on the Neutral Safety Switch circuit contacts

Got it to Crank with transmission in neutral, but no spark to plugs.

1. Tune-up, including Cap, Rotor, Plugs, Wires
2. Replaced Coil (tested bad in primary reading)
3. Replaced Power Stage unit

Other advise I got was to check the tach when cranking to see if it moves. If it didn't could be the distributor hall effect sensor. I get a little twitching when cranking the engine. What next? I am about ready to tow it to my Volvo mechanic, but I've come so far and it is getting better.