IML: Electronic ignition

[Joe Strickland <jwstrick426@xxxxxxxxxx>]

I have been having trouble posting to the IML lately after resubscribing 
and changing to digest mode.  I wanted to share these comments I sent to 
Geoff in case it might help someone else.

Geoff;

Have you had your existing distributor apart enough  to see the 
mechanical spring loaded advance cams?  If not, remove the points and 
the points' mounting plate and check the movement of the spring loaded 
cams.  The cams should move easily by finger pressure and quickly return 
to their resting position.  The pivot points of the cams are lubricated 
and it is possible that the lubricant has dried out.  This can happen on 
both conventional older design distributors and the newer electronic 
distributors.  It shows up as knock or ping under acceleration. Check to 
be sure the vacuum advance and vacuum lines have no vacuum leaks  I had 
a '73 model with electronic ignition which would act that way.  I 
eventually discovered the problem with the cams when I started to 
replace the pick-up reluctor mechanism and star wheel on the distributor 
shaft.  Before replacing the parts I decided to clean and re-lubricate 
the cams and it corrected the ping/knock problem.  I went ahead and 
changed the reluctor element and the star wheel on the distributor shaft 
anyway since I already had the parts on hand.

The car I mentioned above had the exact symptoms you described - pinging 
under moderate acceleration.  If you really got on it, the pinging would 
go away.  It pinged just when you did not want to put your foot into it, 
just normal driving.  It is a subtle condition and difficult to analyze 
except by just removing that upper plate and trying moving the 
counterweights/cams to see if they move freely and quickly, not slowly 
(caused by dried out or gummy lubricant).  I hope this helps.

Joe

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