Spark test

[kurylenko]

Hi there!
I have a small sail boat with an outboard motor - a Yamaha F15AMHS year 2004.
I wanted to be able to check the functioning of the Spark Plug Coil in case the engine
stops working, so I purchased a Spark Gap Tester. It is not the one Yamaha recommends
but it is very similar. Anyway, it is a very simple gadget, with two points enclosed in a
small acrilic tube with graduation, each point connected to a piece of wire, the distance
of the poins being capable of adjustement to the desired measure.
I connected it in the manner recommended by Yamaha but nothing happened. No sparks.
Then I re-connected the the spark plug wires and the engine started normally. I checked
the gadget - everything is OK. I made several tests with same result.
Could anybody explain to me this mystery?

[DennisG01]

Did you connect to a good ground? Was it "bright" where you were looking at the tester?

[kurylenko]

Yes, it was good ground. Also it was placed in a dark place. Yamaha says the gap on the tester chould be 9 mm but it does not produce sparks even with 1 mm.

[panasonic]

Can you take picture of how you have it set up?

[DennisG01]

I'd like to see the picture, too, if you can. But this isn't rocket science - if you've done everything correctly, and are sure the plug wire was seated firmly, then you might just have a bad tester. Can you get the plug to spark (inserted in the plug wire boot) if you hold the threads against the engine block (or a good ground)?

[kurylenko]

Yes Dennis, I will try that. I also will try the tester in my car.

[rodbolt17]

doeas your car use waste spark ign?
maybe there is a reason Yamaha calls for a specific tester.
I use a stevens s-48.
but you must understand how a waste spark coil works and what happens when you open one leg.

[kurylenko]

Sorry for my ignorance but ... what is "waste spark ign"?

[99yam40]

spark has to go thru 2 plugs at the same time
one cylinder is on an exhaust stroke and the other is on the power stroke

[panasonic]

Sorry for my ignorance but ... what is "waste spark ign"?

Your engine has one coil and two plug wires coming out of that coil, is that correct?

When you tried to check the spark using your spark tester, did you have both spark plug wires disconnected from the plugs? Meaning one with the spark tester hooked up to it and the other hanging free?(not grounded)

It seems from your first post on this thread that is what you did.

If you don't have BOTH plug wires grounded from a waste spark, single coil, double spark plug wire set up, you will not get spark on either lead.

I am not 100% sure about this on your engine, but I highly suspect that this case.

I had several motorcycles and snowmobiles with waste spark coils on them and they were like this...I found that out the hard way.

[kurylenko]

Yes Panasonic. My engine is "waste spark ignition" type. When I try to check the spark coil, I connect the two wires of the tester to the two wires of the hi voltage coil. This way it SHOULD WORK!

[panasonic]

Is it a tester for one plug? Does it have a single wire coming from each end?

If it is a single plug tester, meaning it will test only one plug at a time, then connecting it between the two plugs wires will not work.You are shorting out the coil doing that.

Please post a picture of how you are connecting the tester so we can understand what you are doing.

[kurylenko]

[panasonic]

Set up spark tester like this. Both coil outputs MUST go to ground.

[kurylenko]

Yes, I tried this way, same problem.