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Basic Ignition Question

A

Anonymous-0

Well-known Member
Have an 18hp Onan twin,no spark.New points,condensor and new coil,still no spark.Engine grounded good,points set to .017,no fire.Have 12 volts to the + side of the coil,but no output.New wire from coil to points.What am I overlooking?Thanks.
 
Trkr,

You probably know this, but here goes anyway.

1. When the points are OPEN - you should have 12 volts on one side of the points and 0 volts on the other side of the points

2. When the points are CLOSED - you should have zero volts on BOTH sides of the points.

If that is not the case in point #1 above, you have an open coil or a bad wire from the coil to the distributor (points).

If that is not the case in point #2 above, you have points that aren't closing or the points are not getting a ground connection through the distributor plate that they are mounted on. There is usually a small, braided wire inside the distributor that goes from the distributor plate to the distributor housing itself.

Good luck with your diagnosis.

Tom in TN
 
If possible try switching plug wire longest to other side may be a bad plug or wire.

Both fire at the same time one only "Ghost fires "

I know Briggs will run on one cyl .. Don't know why an Onan wouldn't
 
Check to see if the points are moving correctly. The pin that rides on the cam wears out and gets to short. Get the model number because there are about five different setups.
 
Make sure you have the points open when checking battery voltage on both small terminals on your coil. Hal
 
Be sure all the interlocks are in their run position (I am not sure what it is on), but seat switches, deck switches, clutch switches, and gear switches all prevent ignition! Jim
 
Just beacause its new doesn't mean the coil is good.....
But I've found even new points sometimes dont ground properly....I usually install them,then open and close them with a screwdriver....If no spark is present I just gently scrape the contact areas together and check again....Yeah I'm a backyard/junkyard mechanic from way back....
 
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