How to test for spark?

[boatdude100]

3L volvo Penta...
What exactly... is the screwdriver method or similar please?

I recall something like putting a screwdriver in plug boot and placing close to block maybe? Then turning over engine in idle or something like that??
Thanks so much

 

[jimmbo]

That is what it is, of course any paint on the Block can interfere with the Spark, so it is hit and miss. The are Adjustable Gap Spark Testers


Or with a bit of ingenuity, and a piece of Dry Wood, a couple of Nails, and some wire and clips, you can make your own. Only thing is to space the Nails the proper distance apart. 5/16" for points ignitions, and 7/16" for electronic

 

[ChrisinPHX]

Screwdriver and bare metal. All you need. You can always pull a wire and just use a random spark plug too if you have one laying around in a drawer or something.

 

[Scott Danforth]

Screwdriver and bare metal. All you need. You can always pull a wire and just use a random spark plug too if you have one laying around in a drawer or something.

No you want to make sure the spark can jump the correct gap. So use the tester shown above

 

[jimmbo]

Screwdriver and bare metal. All you need. You can always pull a wire and just use a random spark plug too if you have one laying around in a drawer or something.

Sure. As for using a Plug. A Spark jumping a 0.030" gap at Atmospheric Pressure means Nothing. Voltage Requirements go up many-fold when the Cylinder Pressure rises(Denser Air makes a better Insulator). That is the reason for Large Gap for testing

 

[boatdude100]

Excellent responses than you!

 

[tpenfield]

I use an alligator clip wire from the plug to the engine block as the ground. It can be a bit hard to see the spark in direct sunlight. So a shaded area is best.