Dave(at)AirCraftersLLC.co
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 Posted: Wed Jun 04, 2008 8:55 pm Post subject: SlilckStart Troubleshooting |
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If your SlickStart doesn't seem to be starting so slick, read on.
Our RV-10 developed a starting problem in that in suddenly becare VERY difficult to start. For 130 hours it had been starting quite nicely, but the last time I tired, I just had to give up.
N921AC has two slick mags, one with retard points on the left, and a SlickStart solid state starting module, essentially a newer version of the Shower of Sparks system.
I went through all the normal troubleshooting and figured the problem must be the SlickStart module. I wasn't getting any spark at the plug with the SlickStart powered up and the retard points in firing position. I called Unison just to make sure I was checking the right things, and they confirmed it had to be the SlickStart. So I changed it.
No help. I checked as many things as I could think of: timing, p-leads, harness, fuse, grounds.. I knew the points were opening because my timing box was indicating OK. I knew the mag was basically sound because when we had managed to get it started (I won't go into how...), it ran fine with a normal mag drop.
I finally gave up and sent the mag and both SlickStarts (old one and new one) to LyCon, where I got my engine. They put it on their magneto bench, and came up with the following explanation. This is somewhat untested, but it makes sense and all the evidence >>points<< to it. Sorry, I couldn't resist.
Ken at LyCon explained to me that the capacitor had failed, and in so doing had caused the frame of the points (both sets, I guess), to get warm enough to accelerate the wear of the cam follower. So, both points were technically opening, but just barely enough to trip the timing light. Maybe .001 or .002 inches instead of .012 or more. That does make sense, because one of the first things I did was to check the mag timing, and I found it had advanced about 10 degrees, to about 15 BTC on the main points and about 10 past TC on the retard points. I just reset the timing and went on troubleshooting. As the cam follower wears, it retards the spark.
Part of the SlickStart troubleshooting says to look for ~300 volts from the output. If the points were barely opening, I think that 300 volts would be able to jump the gap and essentially ground through the retard points instead of exciting the primary coil.
I installed my old mag after LyCon replaced boths sets of points and the capacitor, and it worked fine.
So the upshot is, if the SlickStart troubleshooting points to a bad module, it's probably worth physically checking the point gap with a feeler gauge, instead of just with the timing box before you replace the module.
In retrospect I wish Unison would have suggested that.
Dave Saylor
AirCrafters LLC
140 Aviation Way
Watsonville, CA
831-722-9141
831-750-0284 CL
www.AirCraftersLLC.com
135 hours
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