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Discussion Starter #1
1999 ZR 500efi

Running on one cylinder only.

Testing revels only shorter of two ignition wires producing spark. Grounding plug to engine head and pulling cord produces big fat spark on short wire and no spark on longer wire.

Measured resistance on both and shorter wire produces more ohms of resistance but I have a hard time interpreting the results. (Don’t know if it was a lot or a little.)

Took coil out of my sled and plugged into my Dad’s 97’ ZR580efi. Grounded plugs and pulled cord. Same result. Only shorter of two wires produces spark.

Questions:
1. Would it be safe to assume the coil is bad? Is it possible to test a coil any other way?
2. Do the plugs fire in a batch-fire? i.e. both plugs fire at the same time, each time?
3. I looked up the part numbers etc and it appears this is about $133 part. I’ve found quite a few on ebay including one from a 99 ZR 700. the part number is different but most of what I see out there looks the same. Even the ones labeled as “new style 800/900” say they fit older models. A coil is a coil basically, isn’t it? I’d figureanyhting 99’ and up should work as long as it’s from a ZR/ZL/Pantera- type twin, right?

Once again I plead for help…….

Joe
 

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Discussion Starter #2
It was suggested on arcticchat that typically if a coil goes bad the whole thing goes bad not just one side. Thoughts on that? Maybe just a wire or cap?
 

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It is unusual for a waste spark type of coil to fail the way you have described. Is it possible, yes, but not the norm.
When a coil fails typically one of the inner windings burns open or shorts to ground and neither wire gives off a spark. It could be a cap (replaceable) or it could be a wire (part of coil anyway) or it could be a coil (helpful eh?)

Anyway, if the coil did not work on yours, and it did not work on your dads, why not try his coil on your sled and see if it works?

You could also resistance test your coil, I do not have the exact specs in front of me, but I would guess (and this just a guess) that primary resistance (between the two low voltage coil wires) should be less than 2 or 3 ohms (many coils like this are 1 ohm or less). Secondary resistance (between the two spark plug wires) should be 5-15,000 (5-15K) ohms without the plug caps installed.

I can look the specs up tonight when I get home,
 

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Discussion Starter #4
Thanks, my dealer said the same thing when i called him about it being unusual for only one side to fail. I was going to try his coil in my sled but wasn't sure of the differences. I didn't want to burn his coil up or something! I'll try first- switching the plug caps. Hopefully it's just a cap. If that doesn't work I'll try the resistance test.

For this you say resistance is measured from one plug cap to the other? We measured from the red (and then black) wire to each cap and got 13-14k on the bad wire and 18k on the good wire. I'll have to try that the right way tonight.

Thanks versitleman!
 

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Your coil works like the following: (ya I know, in the pic, it has valves, lets pretend its a 4 stroke)
The white winding is the primary (your 2 wire connector)
the black is the secondary (both plug wires)
[attachment=33682:coil.png]

-The CDI allows current to flow into the primary winding and this creates a magnetic field in the winding.
-When the CDI turns the primary winding off the magnetic field produced collapses and is induced into the secondary winding.
-This energy, rapidly absorbed into the winding, creates the current that will go from one pole of the winding, through both spark plugs and back to the other coil pole.

This type of coil is sometimes called an isolated step-up transformer. All it means is that the primary and secondary windings are isolated from each other and are not electrically connected.

If you are getting continuity between the primary and secondary sides of the coil, you may have a coil that is internally shorted or carbon tracked.

good luck,
 

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Discussion Starter #6
I tried the new end and sure enough......it didn't work. It must be what you are talking about or the wire could be broke inside. There were no visable cracks in the wire but since they are not replaceable, I need a new coil either way. I bought one on ebay last night frome someone close in NY state but it will still be a couple days for it to get here and it's supposed to be 40 by the end of the week. Would it be possible to temporarily use a coil from a 97' ZR 580efi on my 99 ZR 500 efi until the one I bough arrives?
My brother's 97 ZR has a blown piston and his sled is just sitting there.

The part numbers are different but the coil looks almost the same visually. Would it work? Would it risk damaging the ECU? Risking a $600 computer isn't worth 2 or 3 more days of riding obviously.
 
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