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Ignition problem

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cookflys

Joined: 13 Jan 2009
Posts: 17
Location: atlanta

Posted: Mon Mar 19, 2012 4:30 pm Post subject: Ignition problem

When doing "mag" ck on my 582 turning off one of my ignition sends the rpm off scale.

Sent from my iPad

Charles  Cook

582

Model II

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_________________
Charles Cook
Model II 582
#363

mikeperkins

Joined: 22 May 2007
Posts: 123

Posted: Wed Mar 21, 2012 10:19 am Post subject: Re: Ignition problem

I've not seen this exact problem, but I have a few thoughts based on the assumption that the system once did not perform this way.



The 582 has the Ducati ignition system, meaning it's an electronic version where the coils and the tach are operated by a module. Here are the possibilities as I see them: 



1) There is an open ground either at the ignition switch, ignition module, or the tach. (Missing grounds can make very strange things happen.)  

2) There is a short between one of the ignition cutoff wires ("mag" leads) and the tach lead. 

3) The ignition module is bad.



Here's what I'd do to troubleshoot. 



With all leads removed from the ignition switch, check that it works properly with an ohmmeter (that the keyswitch connects the right terminals in the right positions, and also not in the wrong positions.) Also check for a short between the both mag leads and the tach wire. 



If everything seems ok to this point, or you can't test the switch easily, still leave the switch disconnected and hookup jumpers that can allow you to test-run the engine without the ignition switch - so you can start the engine and do an individual "mag check" with the engine running. See if the tach behaves. 



If the tach still misbehaves, then it's likely a bad ground somewhere on the ignition module or (ugh) a bad ignition module.



I'm sure you see the basic idea - check for problems with the switch and the wiring. . . . and then run the engine isolated from as much of the aircraft wiring as possible to see if the Ducati ignition module is good or bad.  



Hope this helps. 

Mike Perkins

Kitfox Model I (1994)

532 / GSC prop

TC and FA

Electronic Engineer

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_________________
Mike Perkins
Havana, Illinois
Model I, 532, B gearbox, GSC prop

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Wed Mar 21, 2012 2:28 pm Post subject: Ignition problem

It's been a while since I've looked at the schematic for the 582 but if I

remember correctly the tachometer does NOT go through the ignition module

but operates from a separate coil in the magneto.  There have been problems

with the Westach tachometer seeing either too much or not enough voltage on

the tach coil.  My advice is what I did and get a TinyTach just be sure to

wrap BOTH wires to either cylinder so it will read with either mag coil

turned off.



Noel



--

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Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

occom

Joined: 26 Aug 2006
Posts: 404

Posted: Wed Mar 21, 2012 2:58 pm Post subject: Ignition problem

There are a fair number of people experiencing this issue if you use the

proper terms in a Google search. To save you the effort Mike Stratford has

written a number of informative articles on the Rotax engine, always the

first place to look when you have a question IMO. # 49 addresses just this

issue.

http://www.800-airwolf.com/pdffiles/ARTICLES/Part%2049%20-%204%20page.pdf

here is the paragraph quoted from the article. 

Why does my Tach go Crazy During a Mag Check?: Before we get started I have

to answer one of the most common questions about a

Ducati System. Many operators panic when their electronic Tach does not

respond as expected during a Mag check. Knowing how the circuit works one

can actually expect

to get strange Tach readings. The gray wire is connected to a common pair in

the ignition poles with the circuit being completed to thru a ground wire.

This produces the 6

pulses per revolution the Tach is reading. During a Mag check the ignition

voltage is dumped to ground thru a shorting cable (wire #8 in figure #2)

killing one side of the dual

ignition. The pulse or wave can come up the ground wire confusing the Tach

as to the actual pulses being received. Moving the ground wire around will

likely produce mixed

results. Obviously a Mag check will not produce the standard GA rpm drop

many pilots come to expect and there is little you can do to change that. It

is best to just listen for

the rpm drop and ignore the tach. END OF QUOTE



T

he upshot of the paragraph is don't worry about it. Good luck!

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