4-Stroke "wasted spark" Coil Operation?

[bankerjohn]

Any 4-stroke folks out there who know how the coil is wired on a "wasted spark" system?

My E10FREDR motor has one coil, with 1 connection to the ignition module, and 2 plug wire connections. As I understand it, both cylinders fire at (around) TDC on both the compression stroke, and the exhaust stroke ... thus giving it the "wasted spark" name.

What I'd like to know is, how can such a coil produce a good spark to one plug wire, and an lousy intermittent spark to the other plug wire? The only way I can see this happening is if one of the connections internally to the secondary coil is good, and one is failing ... or there are actually TWO secondary coils in the unit, one for each plug wire.

Anybody know for sure how these units are constructed?

 

[dlngr]

Re: 4-Stroke "wasted spark" Coil Operation?

I don't know how they're constructed,but I've had the same problem with an almost new Harley coil years ago. [HDs also run what we call 'wasted spark']

 

[Chris1956]

Re: 4-Stroke "wasted spark" Coil Operation?

Why not feel the bad plug wire for arcing? Also ohm out both wires to the primary winding. One would think that they should have the same resistance. Since you have a two cylinder motor, the sparkplugs need to fire alternately 180 degrees apart. To save the cost of a dissy, they probably have a one lobe points cam and just run two plug wires from the single coil, where they are internally connected.

 

[bankerjohn]

Re: 4-Stroke "wasted spark" Coil Operation?

Why not feel the bad plug wire for arcing?

I'm not sure I understand ... "feel the bad plug wire for arcing"? I've disconnected both plug wires from the coil and the plugs, and put a meter on both of them ... both read zero ohms.

The only reading that's "off" is the resistance between the 2 plug wire terminals on the secondary side of the coil ... the service manual says it should be 2300 ohms +/- 300 ohms ... I read 2630 (just over the max).

Also ohm out both wires to the primary winding.

There is only one wire from the ignition module to the primary coil terminal!

 

[JB]

Re: 4-Stroke "wasted spark" Coil Operation?

Why not feel the bad plug wire for arcing? Also ohm out both wires to the primary winding. One would think that they should have the same resistance. Since you have a two cylinder motor, the sparkplugs need to fire alternately 180 degrees apart. To save the cost of a dissy, they probably have a one lobe points cam and just run two plug wires from the single coil, where they are internally connected.

No, Chris. This is a 4 stroke engine, the cylinders fire 360 degrees apart, with both plugs firing at the same time. . .one on compression stroke and the other on exhaust stroke. Inline twins use a 360 degree crank, opposed twins use a 180 degree crank.

I had a "wasted spark" system on my 1963 BMW 700 Super Sport Coupe with a boxer twin engine based on the bike 700cc twin. (Dang, I loved that little car!!). In that one there was a single primary and dual secondaries in the coil. It really got your attention on a cold morning if the "wasted" spark fired a previously unfired charge with the exhaust valve open !!!

 

[Chris1956]

Re: 4-Stroke "wasted spark" Coil Operation?

You are correct JB, I'm still thinking 2 cycle.

Don't single cylinder lawnmowers have this kind of ignition system?

 

[Sea18Horse]

Re: 4-Stroke "wasted spark" Coil Operation?

Yes a 4 cycle waste spark coil (secondary side) is one coil of wire with one spark plug wire connected to one end and the other plug wire connected to the other end. Your problem is not a poor connection to one coil wire but a short to ground inside that is closer to one end than the other. It happens in automotive d.i.s. ignitions all the time. If you had a low amp probe and a lab scope you could see it very clearly. Basically you just need to check the plug wires as you have done to verify that they are ok and then take an adjustable spark checker and see if both sides of the coil will jump the same size gap. If one side will jump 3/4 inch and the other side will only jump 1/4 inch then it's junk.

Cheers.................Todd

 

[bankerjohn]

Re: 4-Stroke "wasted spark" Coil Operation?

My "NLA" coil arrived in the mail today ... so I will install it tomorrow and report back as to whether that cured my problems!

It's hard for me to understand why OMC/BRP would continue to sell coils for a 30 or 40 year old motor, and discontinue one for a 13-year old. I guess they must not have made that many 4-stroke motors!

 

[bankerjohn]

Re: 4-Stroke "wasted spark" Coil Operation?

#$%^^@$ ... the new coil did NOT correct the problem!

Still getting virtually no spark on one plug wire. The weird thing is ... if I attach the pickup for the timing light about midway on the "good" plug wire, I get constant flashes like I would expect. But if I move the pickup close to the boot on the coil, I get almost no flashes. And intermittent flashes at best on the other plug wire.

I've ordered some new plug wires, but the more I think about it, I really don't think that's my problem ... especially since I'm getting ZERO ohms on both wires.

Is there a simple way to check the timing with the timing light?

Is there a simple way to check the signal to the primary coil from the ignition module (without a "high dollar" analyzer)?

I hate to think that the problem's in the ignition module ... $260+

Any suggestions would be greatly appreciated ... my wife's bugging me big time to go fishing!

 

[bankerjohn]

Re: 4-Stroke "wasted spark" Coil Operation?

Out of desperation, I ordered and installed new plugs wires ... hoping against hope that this might cure my spark problem.

Nope ... didn't help.

Is there a way to test the power pack without some type of specialized testing equipment? If so, how?

Should I first try to determine if my stator is sending the power pack the correct voltage / signal? If so, how?

 

[Sea18Horse]

Re: 4-Stroke "wasted spark" Coil Operation?

I wonder, have you checked for spark with an actual spark checker? And seen if it will jump at least a 7/16" gap and is the same on both wires? Or are you going solely on the flashing of an inductive timing light? Because using a timing light is not a reliable test for ignition system integrity. A lot of things can cause low firing voltage. Shorted/fouled spark plug, low compression, too much fuel. You can get a spark checker at just about any auto parts store for less than $10.00.

Cheers and good luck.............Todd