Ignition Coil or Plug Wire?

[bankerjohn]

My 9.9 Evinrude 4-stroke (E10FREDR, upgraded to electric start) has a problem running at any engine speed other than idle.

I have ruled out fuel tank pickup screen, primer bulb, fuel pump filter screen, and plugs (I installed new ones, properly gapped).

Before I dug deeper into the FUEL side, I thought I'd better check the SPARK. And since I've only got one of those in-line testers with a neon bulb (which you can't see in the sunlight, even if you have a good spark) ... I hooked up my trusty old Craftsman timing light.

If I crank the motor, and I connect the "probe" to the top plug wire, I get a rapid constant flash ... but when I connect to the bottom plug wire, I get very sporadic flashes, with the strobe being OFF much more than ON!

So ... my assumption is that the bottom plug is not getting the proper spark. Is my assumption correct ... or is this not a proper test?

I've attempted to test the coil, but the manual says that the resistance between ground and the primary terminal should be .28 +/- .05 ohms ... and my digital meter just isn't that accurate to properly measure. The other tests to and between the plug wire terminals are OK.

I checked the resistance between both ends of the bottom plug wire, and wiggled the wire around, always getting 0 ohms resistance.

I'm stumped ... should I just order a new coil, and new plug wires, and see if that cures my problem. Or is my timing light test not valid? Or is there something else I need to check out ... like the (shudder) ignition module?

 

[tx1961whaler]

Re: Ignition Coil or Plug Wire?

I think your test seems valid.
I'd go through all of the connectors on the ignition module and thoroughly clean them up first. Unfortunately the coil is now "Dealer Direct" and the ignition module is $360. BRP seems to have orphaned these 4-strokes.....

 

[bankerjohn]

Re: Ignition Coil or Plug Wire?

The more I think about my problem, I'm thinking it couldn't be a problem with the ignition module. My reasoning is ... the motor only has 1 ignition coil, and both plug wires are attached to that one coil. If there was a problem with the ignition module, I wouldn't think that I'd get a good spark on either plug wire!

Does that make sense?

Can anyone explain how the single ignition coil "knows" which plug wire to send the spark to, and when?

 

[tx1961whaler]

Re: Ignition Coil or Plug Wire?

I don't think that it is a single ignition coil. I believe that it is 2 separate coils in one package and the ignition module has two output wires; one for each coil. If you could somehow swap the input connections from the ignition module to the coil(s), and the problem moved to the other cylinder, then the issue would be the ignition module. If the problem stayed with the same cylinder, then it would be the coil or spark plug wire.

 

[bankerjohn]

Re: Ignition Coil or Plug Wire?

Here's a diagram of how the ignition coil and the ignition module are configured:

Unless I'm missing something, there are only 3 connections to the coil ... 2 plug wires, and the wire to the primary connection from the ignition module.

New Info:

According to this quote from Wikipedia ...

"Where one coil serves two spark plugs (in two cylinders), it is through the "wasted spark" system. In this arrangement the coil generates two sparks per cycle to both the cylinders. The fuel in the cylinder that is nearing the end of its compression stroke is ignited, whereas the spark in its companion that is nearing the end of its exhaust stroke has no effect. The wasted spark system is more reliable than a single coil system with a distributor and cheaper than coil-on-plug."

And if that explanation is correct ... it appears that I need a new ignition coil!

 

[tx1961whaler]

Re: Ignition Coil or Plug Wire?

Aaah. Simpler than I thought it was. I assumed that there were 2 connections from the ignition module to the coil.