Engine keeps running

by Donn Fishburn in General Tech Discussion 6 years ago

Do the mag switches in the "ON" position complete a circuit allowing the engine to run, OR do the mag switches in the "OFF" position ground the ignition causing the engine to stop (ALA old dirt bikes)? I ask because today when I tried to shut down one of the mags stayed active and the engine kept running. Fortunately another pilot was nearby and was able to shut the fuel valve; killing the engine.

I need to know where to start troubleshooting - bad switch, bad ground, faulty mag unit, etc.

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Re: Engine keeps running

by Bill Hertzel » 6 years ago

Bill Hertzel

13 1.95k 7.97k

They are "Dirt Bike" Technology.
One side of each switch goes to ground.
Ground = Engine OFF.
Open Circuit = Engine RUN.

It is most likely a bad connection and not a bad part.
Pull the wire Off of the High side of the switch.
Measure the voltage on the disconnected wire.

If you do NOT see a significant voltage, there is no continuity to the ignition module.

While you have the wire OFF, use the Ohms function to check that the switch toggles.

??????????????
Why do you need a second Pilot to turn OFF your Fuel Valve?

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.

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Re: Engine keeps running

by Donn Fishburn » 6 years ago

Donn Fishburn

4 4 4

Being that is is a magneto I assume there would only be voltage on the hot side of the switch with the engine running. Am I correct?

The fuel valve on my trike is not reachable from the Pilot 1 seat and I did not trust myself to get the brake securely locked before getting out.

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Re: Engine keeps running

by Bill Hertzel » 6 years ago

Bill Hertzel

13 1.95k 7.97k

Being that is is a magneto I assume there would only be voltage on the hot side of the switch with the engine running. Am I correct?

A reasonable assumption.
You might also measure ground on the wire if the points closed on a stopped engine.

What engine are we talking about?

[quote]The fuel valve on my trike is not reachable from the Pilot 1 seat and I did not trust myself to get the brake securely locked before getting out.[/quote]
A design feature that should be remedied!
An Engine Out Landing checklist should include a "Close Fuel Shut-Off Valve", instruction.

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.

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Re: Engine keeps running

by Donn Fishburn » 6 years ago

Donn Fishburn

4 4 4

Tested the resistance of both switches. Good switch was 0.1 ohm. The other switch varied with each time it was closed - from 1.2 ohms to 2.1 ohms. That wouldn't prevent a closed circuit and the engine did shut down when both switches were closed. BUT, because the switch didn't close previously and the resistance was high and variable I'm going to replace that switch.

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Re: Engine keeps running

by David HEAL » 6 years ago

David HEAL

23 189 423

I had a similar situation with one of the ignition switches (OTTO brand) on my RV-12. It was intermittent with the failure default mode being ON -- by wiggling the switch side-to-side one could cause the intermittent operation. Fortunately, it was an easy part to replace.

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