Coil Testing - ZR-1 Net Registry Forums

Billy Mild · 01-05-2015

Is there anyway to test a coilpack without removing the plenum?

8cam · 01-05-2015

You can ohm the wires across the cylinders which might tell you there's an issue. Some say it should test below 20k, but I believe the WSM says anything under 30k is fine. FWIW mine all tested below that, and I had one very bad coil and the others were weak.

http://www.zr1.net/forum/showpost.ph...0&postcount=20

Actually testing the coil itself requires some specialized equipment. However the easiest test is to either put a timing light on the wires, or just start pulling wires with the engine idling. If you pull one and the idle doesn't change much then you have a problem. Ground it and test the spark, and you'll know right away.

Billy Mild · 01-05-2015

What were your symptoms for weak coils?

8cam · 01-06-2015

First symptom was rough running. Idle was off, and if I used anything other than part throttle the ecu killed the fuel and it sounded like an old beetle. Kinda obvious.

I ohmed out the wires and got the numbers shown, and nothing was immediately obvious other than they weren't quite right. When I started pulling wires, #4 showed no change in idle which told me there was a problem there. I grounded it, and compared to the other wires #4 had virtually no spark. The other cylinders showed variable spark, so nothing was consistent. The plugs were relatively new so they didn't look bad, but #4 was definitely a little wet.

I knew the problem was either the wires or the coils at that point, so the plenum had to come off. In the end, it wasn't a difficult job and I had it off in less than two hours, taking a lot of extra time. Once I had it off, I tested each wire individually and they were fine. That left coils. One of my coils had a cracked housing, and they were all clearly original, so I had a pretty much 95% certainty they were the culprit. But since plugs and wires are cheap, I went ahead and replaced everything. Problem solved.

Billy Mild · 01-06-2015

I would like to either drive another ZR-1 that is known to be in perfect running condition to compare it to my car. Or have someone who is more familiar with the ZR1 to drive my car and see if it feels okay.

I am battling a sometimes high idle(could be IAC, TPS, or plates sticking), but I notice when the car is cold that it doesn't seem to run smoothly throughout the RPM range. I almost feel like it bucks a bit when in the lower RPM range when the engine is cold.

01-05-2015	#1
Billy Mild Join Date: Aug 2014 Location: Kansas City, MO Posts: 838	Coil Testing Is there anyway to test a coilpack without removing the plenum? __________________ Looking for a ZR-1 1985 Yamaha RZ350-NOT STOCK 1971 Yamaha AT1-Middle of a restoration

01-05-2015	#2
8cam Join Date: Jul 2013 Location: Atlanta Posts: 451	Re: Coil Testing You can ohm the wires across the cylinders which might tell you there's an issue. Some say it should test below 20k, but I believe the WSM says anything under 30k is fine. FWIW mine all tested below that, and I had one very bad coil and the others were weak. http://www.zr1.net/forum/showpost.ph...0&postcount=20 Actually testing the coil itself requires some specialized equipment. However the easiest test is to either put a timing light on the wires, or just start pulling wires with the engine idling. If you pull one and the idle doesn't change much then you have a problem. Ground it and test the spark, and you'll know right away. __________________ Mark '90 ZR-1 #1322 Daily Driver, 64k and counting Black/Gray [IMG]http://i208.photobucket.com/albums/bb49/mlitherland/IMG_0326_zps3d50d8cb.jpg[/IMG]

01-05-2015	#3
Billy Mild Join Date: Aug 2014 Location: Kansas City, MO Posts: 838	Re: Coil Testing What were your symptoms for weak coils? __________________ Looking for a ZR-1 1985 Yamaha RZ350-NOT STOCK 1971 Yamaha AT1-Middle of a restoration

01-06-2015	#5
Billy Mild Join Date: Aug 2014 Location: Kansas City, MO Posts: 838	Re: Coil Testing I would like to either drive another ZR-1 that is known to be in perfect running condition to compare it to my car. Or have someone who is more familiar with the ZR1 to drive my car and see if it feels okay. I am battling a sometimes high idle(could be IAC, TPS, or plates sticking), but I notice when the car is cold that it doesn't seem to run smoothly throughout the RPM range. I almost feel like it bucks a bit when in the lower RPM range when the engine is cold. __________________ Looking for a ZR-1 1985 Yamaha RZ350-NOT STOCK 1971 Yamaha AT1-Middle of a restoration

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01-06-2015	#4
8cam Join Date: Jul 2013 Location: Atlanta Posts: 451	Re: Coil Testing First symptom was rough running. Idle was off, and if I used anything other than part throttle the ecu killed the fuel and it sounded like an old beetle. Kinda obvious. I ohmed out the wires and got the numbers shown, and nothing was immediately obvious other than they weren't quite right. When I started pulling wires, #4 showed no change in idle which told me there was a problem there. I grounded it, and compared to the other wires #4 had virtually no spark. The other cylinders showed variable spark, so nothing was consistent. The plugs were relatively new so they didn't look bad, but #4 was definitely a little wet. I knew the problem was either the wires or the coils at that point, so the plenum had to come off. In the end, it wasn't a difficult job and I had it off in less than two hours, taking a lot of extra time. Once I had it off, I tested each wire individually and they were fine. That left coils. One of my coils had a cracked housing, and they were all clearly original, so I had a pretty much 95% certainty they were the culprit. But since plugs and wires are cheap, I went ahead and replaced everything. Problem solved. __________________ Mark '90 ZR-1 #1322 Daily Driver, 64k and counting Black/Gray [IMG]http://i208.photobucket.com/albums/bb49/mlitherland/IMG_0326_zps3d50d8cb.jpg[/IMG]