1985 240DL driveability

Thanks for the replies to my query earlier. This concerns a 1985 240 DL USA
Federal spec B230F. I've done some more research on this system and it
appears that the ignition and injection systems are completely detached; the
only connection is an ignition primary signal from the ignition control
module to the ECM. Since my car backfires loudly and loses power it appears
that it gets so far out of time that it's igniting unburned fuel in the
exhaust. Sometimes when it dies it acts like it's running backwards before
it kills completely.
I checked the ignition control module--it's one with a vacuum diaphragm on
it, and the diaphragm is torn. (much better design than I imagined...it
appears that the diaphragm operates a variable inductor--this wouldn't wear
out like a variable resistor) I put some cyanoacrylate (crazy) glue on the
diaphragm, and it seems to run a little better, although with less power!?
But I'm sure this won't last, and I'm wondering if anyone has had experience
replacing this part. I'm guessing all used ones are in similar shape. I'm
also wondering what experiences people have had with the distributors. Do
the hall sensors fail intermittently? What kind of luck can you expect if
you replace the distributor with the old kind with vacuum advance on the
distributor? I really don't want to do that, since it's a major step
backwards technologically, but if it's going to cost hundreds to fix this
car it belongs in the scrap yard.
Another question: Once on my old car I had to replace the o-rings for the
overdrive pistons(sluggish, late shift) and the only way you could get these
parts from Volvo was to buy new, larger rings with new pistons with larger
grooves. (Thanks, Volvo, the originals lasted 200,000 miles, don't really
need more expensive replacements that'll last 300k)
Thanks again.

 

The hall sensors do occasionally fail, though when they do the engine
usually just dies. If the ignition control module is the problem you should
be able to get a good used one for under $50. Ideally you'd find someone
else with an '85 240 and try swapping some parts to diagnose the problem.

 

by user dropped his wrench, scratched his head and
mumbled,

The Chrysler lean burn circuitry does little more than push the advance
to 52 degrees BTDC and then retard it in 19 degree steps until pinging
ceases to occur as measured by the knock sensor. If the hose to the
vacuum transducer is removed and plugged the control unit generates a
fairly conventional spark advance curve, when observed on a chassis dyno.
Regardless of how heavy your foot is this will have negligible effect on
your fuel mileage. It will however seriously reduce your NOx emissions (a
good thing).

If testing the dwell shows a reading of 60 degrees or so increasing with
rpm to somewhere in the seventies the control unit is operating
correctly. If the dwell is accurate and the timing does not retard 5
degrees and then advance smoothly to 36-39 degrees BTDC then I would
suspect a bad component on the control unit PCB. Since the entire unit is
encased in clear silicone rubber, replacement is the only practical
option. If you find a used unit with the same part number be sure to
check that the contact pins for the small black, yellow and green wires
from the distributor have the same sleeves as your old one and that the
used one and yours employ the same harness plug.

Bob