rough on one mag on 912ULS

Thomas Asked:

...  I measured my coils and found the lowest to be 15, 150 ohms, and the worst was 16, 490 ohms.  Just curious if you would see that as satisfactory? 

I am not sure what you measured???

The primary (Low Voltage) side of the ignition coil is less than 1.0 ohm.

That is not resolvable on any consumer-grade ohmmeter. It will just show as a short or some low value.

The secondary (High Voltage) side of the ignition coil is around 6,500Ω more or less.

The plug connectors are around 5,000Ω more or less.

Measuring from one plug connector to its matching connector on the other side of the engine should measure 15,000- 20-000Ω more or less as this involves the ignition coil and 2 spark plug connectors in series.

- - -

Be sure you are using your meter properly.

Touch the leads together to get an idea of how Zero gets displayed.

Many digital meters have an OHM (Ω) selection an also a DIODE selection.  They are not the same.

You will want the OHM selection for this measurement.

Pay attention to what range the meter is on.  The decimal point moves with the range multiplier.

- - - 

Attention Rotax-ADMIN:

The Rotax 912is Heavy Maintenance Manual has a Typo.

In section 76-70-00, Sensors and actuators,  Page 23.

The Secondary Side Measurement is shown as 8.2Ω +/- 0.8KΩ ...  It should read 8.2KΩ +/- 0.8KΩ

Hi again, Bill

Uh oh.  I'm in trouble again.

I saw "... from one plug connector to its matching connector on the other side of the engine .." but I thought we had pinned it down to 1&3 top for an example?  Is it actually 1&2 top, going across the engine?

Yes, 1T-2T. 3T-4T ...

The 912's are Boxer Engines the 1 and 2 cylinders go Up and Down together while the 3 and 4 do the opposite Down and Up.

When the #1 cylinder goes UP in a compression stroke, the opposing #2 cylinder goes UP in the Exhaust stroke.

The spark fires in Both cylinders at the same time. The one in the exhaust stroke is harmlessly wasted.

Thanks again, Bill!  Yes, I knew about the firing-on-exhaust fun.  Fun :-)  But checking resistance is new to me, so I want to be sure to get it right.  Across the engine it is!

Bill Hertzel wrote:

Thomas Asked:

...  I measured my coils and found the lowest to be 15, 150 ohms, and the worst was 16, 490 ohms.  Just curious if you would see that as satisfactory? 

 

I am not sure what you measured???

The primary (Low Voltage) side of the ignition coil is less than 1.0 ohm.

That is not resolvable on any consumer-grade ohmmeter. It will just show as a short or some low value.

The secondary (High Voltage) side of the ignition coil is around 6,500Ω more or less.

The plug connectors are around 5,000Ω more or less.

Measuring from one plug connector to its matching connector on the other side of the engine should measure 15,000- 20-000Ω more or less as this involves the ignition coil and 2 spark plug connectors in series.

- - -

Be sure you are using your meter properly.

Touch the leads together to get an idea of how Zero gets displayed.

Many digital meters have an OHM (Ω) selection an also a DIODE selection.  They are not the same.

You will want the OHM selection for this measurement.

Pay attention to what range the meter is on.  The decimal point moves with the range multiplier.

- - - 

Attention Rotax-ADMIN:

The Rotax 912is Heavy Maintenance Manual has a Typo.

In section 76-70-00, Sensors and actuators,  Page 23.

The Secondary Side Measurement is shown as 8.2Ω +/- 0.8KΩ ...  It should read 8.2KΩ +/- 0.8KΩ

 

 

 

 

Bill, I used the matching plug connector method as suggested by Garrett Wysocki and as you described in your last paragraph (measuring from one plug connector to the matching plug connector).  Just trying to nail down my B ignition misfiring.  Looks like my high voltage side readings are in the ball park and my problem may be on the primary side of the ignition.  At this point, I am not having fun.  Thanks for the reply........Tom