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Message-ID: <4B095C5A.3050708@gmail.com>
Date: Sun, 22 Nov 2009 10:44:26 -0500
From: Steve Brooks <cozy4pilot@gmail.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Ground isn't ground
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The mystery of my intermittent spark is solved.  Thank you to all of 
those who made suggestions, as it helped get to the bottom of the issue.
This morning I decided to repeat the test I made yesterday hooking the 
starter to a separate spare battery that I had.

This time I removed both the large cables going to the starter and 
engine block ground.  That way, I didn't have to mess with a jumper 
cable.  I hooked up the battery, turned the master on and engaged the 
starter.  To my utter amazement the spark was intermittent again.  I 
thought thgat certainly I hadn't made a mistake yesterday an imagined 
that the spark was good on a separate starting battery.  After some 
swearing, I thought about yesterdays test, and the only thing different 
was the ground cable.  So, I removed the ground cable from the 
battery,and hooked up a jumper cable from the negative terminal of the 
battery, and hooked it up to the reduction drive plate, as I had done 
yesterday.   Cranked the starter and had good spark.  Did it twice, just 
to make sure.

What the **** !

So, I decided to connect the jumper cable to the ground cable end, 
instead of clamping it the the reduction drive plate.  Cranked the 
starter, and had intermittent spark again.  Somewhat amazed, but onto 
something here.

I measured the cable (0 gauge multi-strand silicone) with the Fluke 
meter, and it showed pretty much zero ohms.  I measured from the spot on 
the front engine housing where I had the ground bolted on to the 
reduction plate, and measured about 3 tenths of an ohm.

Since my original installation, I always had the ground cabled bolted to 
the front housing, with a bolt into one of the tapped holes where the 
air conditioner mount was.  It is a pretty large bolt, and I never 
suspected that, considering all of the bolts that hold the engine 
together, and the many bolts that hold the reduction drive plate, that 
there would be any issue.  Boy was I wrong.

I reconnected the cables to the main battery, instead of the spare 
battery, and instead of bolting the negative cable back on, I used the 
jumper cable to connect to the reduction plate again.  Perfect spark 
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

My current ground cable isn't long enough to reach from the battery to 
the mounting plate.  I found the cable that I had left, and I have 
plenty of spare cable, but I don't have any more of the lugs for the 
ends, so I will have to order some.  I am going to attach to ground 
inder one of the mounting bolts for the starter. 

Regards and thanks for the help,

Steve Brooks