# New Coil Advance mechanism



## G.MAN (Jul 8, 2012)

[BHow do the new ignition coils advance? And how to troubleshoot them.


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## paulr44 (Oct 14, 2008)

Okay. I have to break this to you. There's no such thing (using Kohler's term) as Spark Advance. That is, on conventional flywheel based ignition systems. Spark Advance sounds a lot sexier than what it really is, SPARK RETARD .You COULD call it, Spark Advance Control which would be more accurate. When dealing with a coil you can't move, a flywheel that's keyed to the crank, you can only build it too far advanced for idle, and then retard it electronically for that idle/low rpm range. You can't advance a system electronically that is mechanically fixed.

When talking about troubleshooting, what do you mean? If you're talking about testing it for advancing (ok, in reality retarding when it should, and not retarding when it shouldn't), then you need an old-school timing light. NO OTHER tool can test that for the money. A complex EFI system allows you to plug in like ODB cars have, and may be able to tell you, but that's $$$.

You've been here and undoubtedly working on engines awhile, so you know that the solid state ignitions USUALLY either work, or they don't. As for the variable timing factor, again, you'd need a timing light. Chalk mark a line on the flywheel screen, shine the light on the screen at idle to locate the chalk mark, and while doing that rev the engine up and the mark should move counter (reverse) to the eng. running direction.

If you're still unsure, I'll explain it differently.

The flywheel magnet approaches and peaks over an ign. coil.
At at that moment, the magnetic field is strongest in a normal system the points would open, or the trigger would fire, either of which would collapse the coil primary circuit and thus force the coil secondary field to function and produce a spark.

In a CDI or Spark-retard system, the capcitor(s) in the coil charge(s) up with the primary voltage, and hold it until the on-board system pre-determined point in time says to fire off the secondary system(s).

Now, to "advance" the system, you have the flywheel timed ahead of what a normal fixed-timing system would be, so you don't want the spark to occur at that too-far-advanced point at low RPM or idle. SO, the on-board system sensing the RPM holds it's trigger time a bit, thus providing spark at a later time, IE closer to TDC. From there, it shortens up the time to fire from magnet peak time as RPM increases.

Advanced ignition timing is required for proper high-RPM operation.
Retarded, or in other words a starting point, is required for low-speed operation.

Cars used to have both mechanical and vacuum advances, which truly advanced timing as they either moved the breaker plate or rotated the point cam lobes relative to the shaft it sat on top of (the distributor drive shaft driven by the cam).

OPE engines, having flywheel based ignition therefore have FIXED timing. That timing index, instead of being say 8 degrees BTDC (good for idle), or 36 degrees (good for high-speed), have to have a COMPROMISE in timing for acceptable performance across the RPM range.

So, if you'd like more theory, I'll give you my 900 number!

Paul


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