|
Hi
Tracy,
I hope you're refreshed and in a
really good mood after your vacation.
Thanks very much for
the report. I'm responding in detail here in case others can learn from my
misfortune....
I have good
news, and I have bad news.
First the good news.
Howard (Cozy builder from Clearwater who is something of an
electronics wiz and has visited you recently) flew down here today and worked
with me for 9 hours on the plane.
I have been suspicious of my coil disable circuit. I discussed
this plan with you by phone many moons ago when I was installing it. Perhaps you
didn't follow what I was planning to do. I connected the center pin on my
standard Left, right, both ignition switch to the EC2 ground, then connected the
coil disable pins on the EC2 to the left and right mag terminals on the ignition
switch. This way "off" would disable both coils, Left would disable leading,
etc. The setup has been like this from day 1. Today, while waiting for Howard, I
put a volt meter between the center pin of the ignition switch and ground, and
cranked the engine. Would you believe 1.5 volts? Second time I tried it the
reading was just a few millivolts. Next time it was 1.5 volts again, then I
couldn't duplicate it. 1.5 volts down the coil disable ground wire would be a
bad thing - right?
When Howard arrived
the first thing he produced, without any prompting, was a schematic for the
standard ignition switch produced by Bob Nuckolls which carries, in very small
print, a warning not to connect the center ground pin to any other ground in the
aircraft. Oops. I have the same schematic in my folder of circuit diagrams, with
the same warning. I guess I missed it. We tested
with his computer logging equipment and couldn't repeat the problem. In
any case, I have separate switching for the coils and have removed this wiring
since the function is redundant anyway.
We went on
to identify significant "ground bounce" in the coil circuit which led
to remaking the coil harness and replacing the existing crimped single ground
with a soldered and crimped ground wire from each coil. Howard also pointed out
that the CAS cable and some sensor wires, including the intake temp wires, go
very close to the coil leads, are bundled with the heavy starter wire, and
should be moved. The engine ground was a bit weak and the ground strap was
cleaned and reconnected. The coil grounding was much improved after all
this.
All in all we
identified a number of ground leaks, loops and bounces, any and all of
which could have been causing problems. Additionally, Howard left me with a very
simple, cheap and extremely useful testing setup made with two voltmeters and a
D cell battery which allows me to test a circuit under load and identify
any weak connections, bad crimps, cold solder joints etc. With this little gizmo
I am newly empowered, and have a lot more testing to do.
And now the
bad news...
I'll have plenty of
time for testing. After 8 hours work in a very hot hangar it came time to
connect Howard's circa 2001 EC2 to my harness and see what we had. As I was
working in the back of the plane to hook up the EC2 to the harness Howard walked
around, stopped me, and insisted that I hook up the ground first. So, I
hooked the ground wires to the EC2 ground pin, but it was a little dark in
the back, sweat was dripping in my eyes and I missed one. Guess which one. Yep -
the main ground lead for the EC2. You probably don't need to read the
rest.
We powered the
system up and cranked the engine with the data logging equipment hooked up to
the primary injector 12v lead. The was no data. This was when I noticed that the
EM2 now had a blank screen. To cut a really long story to just a long one I'll
cut out the Indian war dance, and the fist through the hangar wall bit and cut
to the chase - I managed to fry $1800 + worth of electronics in 5 seconds by
failing to spot one important little wire in a bundle. This, perhaps, will
explain why I can't sleep and am typing this at 4am. :(
So, the EM2 board
(please shout if you need the screen too) will be on its way back in the
morning. I'm not even addressing it - it knows its own way. Also,
eventually Howard's EC2 is going to need a little extra work when it
comes back in for its upgrade.
Finally, just to end
on a good note - a suggestion I made to Howard seems to make sense for novices
like me who are installing equipment that doesn't react well to volts in the
wrong places. A simple 37 pin male female adapter with a few diodes and leds
that glow red when there's a voltage on an inappropriate pin. Green LEDs could
be used to indicate cold start, program store and even mixture and program
voltage by dimming. With a little thought and $5 in materials I think even I
could probably hack one of these together. You could probably do it in 20
minutes. You could ship one of these little "EC2 Savers" with every EC2 for use
and return by the builder. A similar 15 pin EM2 saver could also be built.
This might save you a LOT of warranty work.
Regards,
John (not accepting
calls today)
|