You either have two trigger points not making (or breaking) contact, or a bad ECU. You also could have a flaky wiring harness, or a bad ground connection -- typically ALL of the injectors ground at the same point on the firewall (all eight brown wires from the injectors and some other ones, too). Check that spot, a little corrosion there will play merry hell with the injection system!

Most likely the trigger points. I assume you've check the firing order and haven't swapped any wires around (don't laugh, I'm dyslexic and do that stuff all the time, even check twice and still have it wrong!).

Verify that they open and close as installed in the dizzy by pulling it and checking resistance between the contacts in the plug as they open and close -- I don't know which ones are which, as the SL dizzy uses a different connector than the 72 does. I'd remove and flush with brake parts cleaner first.

I would also drag a dollar bill between the ignition points to make sure they are clean -- they crap up badly for some reason, and since there is essentially no current flow (they only switch the transistor box), a little dirt will cause all sorts of trouble.

It will run pretty smoothly as a four cylinder if the right "banks" are out, but it has MUCH more power on 8 cylinders.....

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!