Forgot to ground spark plug wires during compression test

[Snappermullet]

Just did a compression test on my 90HP V4 Johnson Ocean Runner (1998) which has OIS. Was in a bit of a rush and forgot to ground the spark plug wires. Very annoyed with myself. After the test it seems fine. Starts/runs/idles fine. What are the chances of damage having been done by this?

Its getting serviced in 2 weeks - should I get them to check anything? If so what do I ask for?

thanks

 

[jimmbo]

Welcome to iboats.
I doubt any damage was done. But I'm sure someone will say I am wrong and that you should be forever worried the Ignition system could quit at anytime between now and eternity, which in reality could happen, whether or not you left the leads ungrounded

 

[F_R]

If it still starts and runs, it is fine. Find something else to worry about.

 

[Snappermullet]

Like how do I get all my work done in time to go fishing this weekend?

Thanks for the replies and welcome.

 

[fhhuber]

Got away with it this time...

Doesn't mean you can get away with it again.

It either causes damage or it doesn't when you fail to ground the plug. Its likely to cause damage so you're supposed to ground them.

 

[Chris1956]

Gee, leave the ign key off and jumper the starter solenoid to crank the motor...no worries then.

 

[Strangeleak]

Grounding them does allow the voltage to "find it's way home safely". I doubt you damaged anything considering how briefly the engine is cranked for compression testing. Another reason to ground the plug wires during the test is to prevent a spark from jumping air near your spark plug hole and turning your engine into a flame thrower.:flame:

 

[boobie]

Agree 200% with the above. Had it happen to me and it's not fun to be in a ball of fire.

 

[F_R]

I've done it too. Flame shot out about ten feet. Sure glad I wasn't standing in the way.

 

[interalian]

Hmmm, I think I'm going to try it - OMC flamethrower. Would it belch more fire with the primer pressed in? Experiments will tell.

 

[Faztbullet]

What are the chances of damage having been done by this?

0.00%...........it is done for safety reasons only...

 

[w2much]

If you did not smell hair burning you are OK. As faztbullet says, it is for safety.

 

[F_R]

While I agree, the main reason is for safety, there is some basis for the idea that it can damage the ignition system. In normal operation, the spark voltage is self limited to whatever it takes to fire the spark plug. However, the ignition system is capable of developing way higher voltage than that. If there is no spark plug present, the unusually high voltage looks for an alternate route to ground. If there is a weak spot in the insulation of a (cracked??) coil or plug wire, the spark may arc through that weak spot, burning a hole through it as it does. On the other hand, it could be argued that the marginal part would soon fail anyway.