Spark question

[EJ3]

1977 55hp Johnson, but I don't think that matters.

I pulled the spark plug out, reconnect the it to the plug wire, hold it close to the block and turn the engine over a few times. I get a spark, nice and blue! Both spark plugs do this just fine. I have visually inspected the plug wires and they seem fine.

My question is...

Since I have spark with the above test, does that indicate I would have a spark at idle RPMs, WOT RPMs, and everywhere in between?

 

[F_R]

Re: Spark question

Actually, it only means that it isn't completely dead. Other than that, it is not a spark test at all. You are only making it jump a .030-040" gap. It needs to jump a 7/16" gap in open air in order to properly evaluate the condition of the ignition system.

 

[HighTrim]

Re: Spark question

Not necessarily no. You could lose spark for a number of reasons, 1 being a coil heating up and failing. Inline spark tester is the best test.

Sorry FR, same time.

 

[ezeke]

Re: Spark question

Many engines require 300 RPM for the ignition system to work and produce good spark.

The reason for testing with the spark plugs removed is to eliminate the possibility that the ignition system is basically fine and that the starter is not turning fast enough under load.

For example, if you had good spark on all holes with no load, you might reasonably assume that the power pack was OK.

 

[HighTrim]

Re: Spark question

THis is what FR was referring to