Ignition coil/spark plug wire question

Matt Rain

Matt Rain

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On the 403 to Niagara Falls earlier this week, I suddenly felt a mild loss of power. Turns out, one cylinder stopped firing. My 3 other cylinders seem to be firing/heating up correctly (confirmed with infrared thermometer), so I assumed that the one wire had gone bad.

I took the wire off - my bike has hardwired coils, but I was still able to pry out the cable cleanly. I can see a metal connector and pin deep into the coil. I put in a brand new wire, but it's still not firing. Now, the new wire's core is carbon instead of metal like the other ones - would that matter?

Can a coil be half-bad, or should I simply try to jam in a metal-core wire?
 
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Did you perform a spark plug test?
ie get a spark plug, hook it up to the ignition coil wire and ground via engine. Did you see a spark?

Have you tried swapping spark plugs?
Ie. take from cyl 2 and swap with cyl 3.

Have you tried swapping coils?
Ie. swap coil 1&4 and 2&3(if this is the case of having 2 coils)

If its a carb system
check to see your carbs. Maybe it needs resync or clogged main jet

When youre low of fuel, put 1/5 of seafoam. This will clean your fuel system from junk/carbs a little.
 
I've had a coil go bad on me(I think), but it affected both cyl. Maybe bad wire...try a metal one. If the wires are hardwired to the coil, how did you swap a carbon one in correctly?
 
Riceburner said:
If the wires are hardwired to the coil, how did you swap a carbon one in correctly?
Click to expand...

Like I said, the original wire came out with a bit of prying and it came out cleanly.

I basically jammed the new one in since it looked like the pin at the bottom of the coil would make contact and hold the wire in. It does hold the wire in place.

You guys seem to be confirming that a bad coil would affect two cylinders (2 & 3 in my case).

I shall try a metal wire next.

I've already ordered a pair of replacement coils, but I'd love to have a temporary fix while I wait for the new parts.
 
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Jimsun said:
Did you perform a spark plug test?
ie get a spark plug, hook it up to the ignition coil wire and ground via engine. Did you see a spark? I did. No spark on cylinder 2.

Have you tried swapping spark plugs? I did. Even bought a new set of Champions just to test. No go.
Ie. take from cyl 2 and swap with cyl 3,

Have you tried swapping coils? Haven't tried that, didn't know you could. I assume that I need to swap the molex connectors as well?
Ie. swap coil 1&4 and 2&3(if this is the case of having 2 coils)

If its a carb system
check to see your carbs. Maybe it needs resync or clogged main jet

When youre low of fuel, put 1/5 of seafoam. This will clean your fuel system from junk/carbs a little. Thanks, I shall try that if the replacement coils don't fix the problem.
Click to expand...

My answers in red. Thanks for this btw.
 
Matt Rain said:
My answers in red. Thanks for this btw.
Click to expand...
Hey disregard the carb synch and the seafoam as your problem is electrical.

Did you check your points? Cam chain readjusted?

it seems like its a bad coil. But a bad coil should affect both (rarely 1). In your case its just one. Check for corrosion. In the whole assembly. If no luck, try swapping coils (assuming its the same part number)

What do you mean metal wire it through? Coils do give a good hock you know. Its 12v with a nice ampere
 
Jimsun said:
Hey disregard the carb synch and the seafoam as your problem is electrical.

Did you check your points? Cam chain readjusted?

it seems like its a bad coil. But a bad coil should affect both (rarely 1). In your case its just one. Check for corrosion. In the whole assembly. If no luck, try swapping coils (assuming its the same part number)

What do you mean metal wire it through? Coils do give a good hock you know. Its 12v with a nice ampere
Click to expand...

Didn't check the cam chain. At this point I'm assuming that it's a simple faulty wire. But I'll check it tonight.

And I guess I'm suspicious of that Accel carbon-core wire. It doesn't look or feel like something that conducts electricity (!) I tried jamming it in directly onto the pin/connector on the coil, then I stripped a good inch of the wire down to the core and I wrapped the core around the side of the insulation so that it would hopefully make better contact with the coil pin/connector, all with no luck. Also tried using the same old NGK boot instead of the one that came with the wire.

The coils have a little corrosion on the ground posts but nothing out of the ordinary - I easily took care of that with some electrical contact cleaner and a wire brush. Both coils test right at 3 ohms too.

I may be wrongly prejudiced against carbon wires, but I feel the urge to try a metal one.
 
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I haven't gone over the replies in detail yet, but did you check the wires that run frmo the main wiring harness into the coils?
 
In matts post, youcan either fish the main feeding the coil or sinply swap coils. If its still the same faulty wiring then that give you an ifea of where to go

the reason i said cam chain and points system (if you have this) is because my buddy had an issue of one cylinder dying after coming over. He called me after he got stuck at the lights and we just did the points and cam chain. Make sure that there is spark in the points system.
 
Pretty sure that my bike has an electronic ignition system, but I'll check for that as well, thx.
 
Back up for a second here. I suspect what the problem is - having gone through ignition headaches with my roadrace FZR400 this past summer.

You say it quit running on one cylinder. That is a major clue right there. The ignition system on that bike (and virtually all inline-four bike engines that pre-date the modern individual-coil-on-plug era) uses a wasted-spark system in which each coil simultaneously fires two cylinders.

If there is a fault with the low voltage side of the ignition coil itself or with ANY of the low-voltage control signals upstream of the ignition coil, it will knock out TWO cylinders - and they will be either 1 and 4, or 2 and 3, because those are the ones fired by each coil. So you can rule out the crank position sensor and the ECU and all of the low voltage wiring. If it's running on three, then all of that is working.

Most likely problems: the spark plug itself, or the plug caps. There is a remote possibility that the ignition coil has an internal fault but I doubt it.

There is a specification in your manual for the resistance through the coil, on both the primary (low voltage) and secondary (high voltage) sides. Check it. Make sure you have continuity all the way through both plug caps that are fired by that coil.

Don't forget that you can check for spark quite easily using a spare spark plug - just unplug the cap in question and plug it into your spare spark plug with that plug resting against a good solid chassis ground (the cylinder head or the frame). Mandatory safety warning, do NOT touch it or even come close. Crank the engine over and watch for spark.

In my particular case, the pin inside one of the plug caps that projects into the plug wire had disintegrated.

New set of copper core plug wires, made sure they are seated as firmly as possible on that pin inside the coil, new plug caps, my bike hasn't run this smoothly in years.
 
Fixed! Seems like my first few attempts at jamming the cable in the coil weren't good enough. I crimped a metal ring over the cable and bang, we got a spark. :cool:

Will still replace the whole thing when I get the new hardwired coils, cause my hack is just that, but it's good to know that it was just the wire.

Thanks all!
 
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