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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14440
Experience:  Certified on Onan and Generac generators
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I have a 20 hp onan engine and have lost my spark, coil seems

Customer Question

I have a 20 hp onan engine and have lost my spark, coil seems ok with a test from ohm meter. What could the problem be ?
Submitted: 6 years ago.
Category: Small Engine
Expert:  Hank F. replied 6 years ago.


What are the readings you get on the coil?

The primary winding should read 2.9 - 3.6 ohms, and the secondary winding should read 14,500 - 19,800 ohms.


If this is good, the problem is most likely in the electronic ignition module. Fortunately, it is very easy to test with a voltmeter.



Disconnect the spark plug wires. Disconnect the red and black ignition module wires from the terminals of the coil. Run a 12V jumper to the red wire. Set your meter to VDC and connect the negative lead to a good ground. Connect the positive lead to the black wire coming from the ignition module. Slowly turn the engine over by hand. The meter should read 12V for 1/2 revolution and drop to about 1V for the other half revolution. Turn the motor through at least 3 full revolutions.


What happens?


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