My specific symptoms were a seeming loss of guts. This started
around 400 hours.Compression checks both types said the mechanical parts
were OK. Occasional shakes, sort of intermittent, slower climb and cruise,
rough running during approach to landing. Sometimes the "mag" checks were
worse than others but not really bad. A remark by a mechanic that had worked
on Rotaxes set me on the right track. He said that they had a lot of trouble
with the very hard stranded wire that Rotax used, breaking strands and
getting intermittent. The result is marginal electrical power to the
ignition module giving weak or missing sparks
You sound like your electrical knowledge ends at flipping the
wall switch up to get lights. So forgive me if I'm too basic. First get a
cheap DIGITAL Volt/ohmmeter. They are much harder to break. Get at least 2
short test leads with small alligator clips on the ends. Radio Shack is a
good source. Test each one by clipping to the red and black leads in the
lowest ohm setting. should read zero or less than 1 ohm. Not too gently pull
on the wires to the clips. If any are intermittent, solder them or throw
them away. The meter comes with test probes that have dull points which are
OK for some tests but when you run out hands, use a clip lead for connecting
the probe to what you want to test and use your hands for jiggling the
connector or wire while watching the meter. If the readings jump around you
have located the part with broken strands or a bad connection.
I had a very intermittent partial failure in the red wire that comes
out of the alternator where it enters the 1 pin connector that delivers
power to the ignition module. I disconnected the lead, jumpered the black
probe to the engine. Test this by getting zero ohms when you touch the red
probe to another part of the engine. Shove the red probe between the
connector and the plastic cover on it. Now hole the connector and wiggle the
red wire. The meter should read 4 ohms(this is the resistance of the coil in
the alternator or magneto generator in Rotax speak) (I think, maybe 40 ohms)
steadily as you gently move the wire. If the readings jump around, and a
gentle pull causes them to jump way up or show open, you've found the
problem.
Another trick is to get a straight pin hook it to the meter with a jumper
wire and slide it under the plastic cover to make contact with the point
being tested. You can push the pin thru the insulation on a wire to check
for voltage or continuity ( this may make a high resistance contact, OK for
voltage checks but not reliable for resistance checks as it adds false
resistanc to the reading.
Now for the fun part, fixing it. Buy AMP brand crimper and parts
if possible. Also get a wire stripper with graduated notches for each wire
size. You will probably have to go to an electronics store other than RS.
get the blue connectors (color = wire size) Ask the salesman (sexist) to
teach you how to crimp, using your parts. For wire, I had a high grade test
lead. They have fairly tough insulation and 2 or 3 times the number of
strands of wire than the Tefzel stuff from spruce. These finer strands will
flex much more before breaking. Pomona is a good brand to use. Yes the cost
3 to 5 bucks but do it right. Test your crimping skill by pulling firmly
about 30 pounds to test and get it right before you leave the store.
Cut off the bad connector, use an inline splice to connect the
red wire to the test lead, cut it about 3 inches long and install a new
plug. ( I got some bullet shaped single male blue connectors from an auto
store. This is easier and more reliable than prying the cutoff plug apart
and recrimping it) Now use small tie wraps to tie all the wires together so
that jiggling is minimized. Last but not least do the other one because mine
failed 2 months later.
Leo Corbalis
----- Original Message -----
From: "Dave Anderson" <dja767@charter.net>
Subject: Europa-List: Carb balancing
>
> The comments are helpful on trouble shooting this situation, thanks.
Unfortunately, they are mainly helpful in determining that I have done what
is needed so far with no success. The first thing I did was balance the
carbs as I have done in the past using a twin engine manifold pressure gauge
connected to each side the engine. That has in the past been very effective
in getting the engine balanced and smooth. I founf a very slight imbalance,
but that is now gone. The problem is that although the imbalance is gone,
the engine is running exactly the same as it was before. If it were carb
balance, I would not think it would have a narrow range of rough running.
This thing is "missing", not just vibrating. I have worked with engines for
many more years than I would like to admit and this engine is misfiring on
both ignitions in a way it would due to mixture. I am now checking the fuel
pressure readings and will do a flight to see what those values are doing
with respect to what!
> they should be doing. I need also to check the function of the float
valve to insure there is no leak there. The bottom line is that the engine
was running smoothly and now is missing in a fairly narrow range of power
setting.
>
> Dave
> A227
> Mini U2
> 232 hours TT
>
>
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