only one dead coil

[elklake]

1979 140hp merc. #3 no spark.i took coil pack off and cleaned behind.No good.So i took #2 coil wire off switchbox put it on #3 coil no spark.Rechecked #2 had spark. Is this a good way of testing? I just thought it was a little weird that only one post on box would go bad. And it has a brand new trigger.

 

[Laddies]

Re: only one dead coil

As good as any

 

[Texasmark]

Re: only one dead coil

Not familiar with your rig. IF you have an epoxy sealed unit with multiple outputs your sealed unit could contain separate solid state switching devices for each cylinder.<br /><br />With that said, it sounds like one is defective. Not uncommon in the electronics industry to have malfunctions. Most are infantile so they do things like "burn in" components and systems to weed out premature failures. On outboard motors, I doubt this is the case.....too expensive.<br /><br />On a coil and points setup, one switch (points) fires every cylinder so if the points fail the whole engine is dead.<br /><br />Mark

 

[WillyBWright]

Re: only one dead coil

I looked up a 1979 140 and it showed a distributor with a single coil. Give us a serial number. But it sounds like you have ADI ignition which has a separate coil for each cylinder. Since the dead coil lit up when the lead was changed, your problem is probably on one of the two switchboxes. It could be the one with the dead lead, or it could be the other since they're paired together.

 

[elklake]

Re: only one dead coil

Hey thanks.I will look for s.n. i will have to look in book to findout where it is. It is ADI ignition. And just for grins when the book tells you to hold plug and wire 1/4 inch. away from block to test for spark i sure hope they mean with rubber gloves. I can't beleive i fell for that.Later.

 

[AMD Rules]

Re: only one dead coil

There's a nice video here that shows you how to check for spark. Its not a Merc, but the concept is the same.