[mrbeetham]

I was recently loosing spark to one of my cylinders once my bike got up to running temperature. Figuring it was a coil problem I ordered a replacment coil. I have fitted this new coil but it doesnt deliver spark to either of the 2 cylinders it is supposed to. My first guess was that i had been sold a lemon, so, i refitted my old coil to find that it also does not deliver any spark to either cylinder. The fact that neither this "new" coil, nor my old one (which always worked ok when cold) give any spark leads me to think that its not a coil problem but something earlier in the line.

I tested the voltage across the 2 wires that attach to each coil (not the HT leads but the other "skinny" ones) and get a reading of 9volts for both my 'good' and 'bad' coils when i crank the engine. This seems about right to me.

Is there anything else that could cause a problem like this aside from dodgy coils?? I dont want to accuse the guy i brought the new coil from, of selling me a lemon if it is actually something at my end.

Any suggestinos would be greatly appreciated.

Cheers.

 

[utp216]

You checked the (if my memory is correct) the Orange w/ White tracer wire going to both of the coils? That wire on each coil should have +12V going to it as soon as you turn on the key and have the "ON" switch turn on. These bikes switch the ground on/off with the ECU to fire the coil packs.

I would go about checking the ECU connection and maybe even swapping the ECU with one that you know works.

Another place to check is the trigger on the end of the crank. It is behind the small cover on the right hand side of the motor. If somethine is messed up in there or with the wiring it will send the wrong information to the ECU and might never fire correctly.

 

[mrbeetham]

Sorry i forgot to say that its a 1989. Did they already have ECU's back then?

Ive been doing some research and the best i could come up with is that it may be a problem with the CDI. Im going to go and just test everything i can get my hands on, to see if i can find anything unusual.

 

[utp216]

Sorry i forgot to say that its a 1989. Did they already have ECU's back then?

Ive been doing some research and the best i could come up with is that it may be a problem with the CDI. Im going to go and just test everything i can get my hands on, to see if i can find anything unusual.

Pretty sure they still had a solid state ECU in '89. Is your bike the oil cooled GSX-R? You might want to post in that section. Lots of guys that know a lot about those model bikes!

 

[fireforeffect49]

Like utp said, it ain't the coil. You should have about 12v across the coil w/ the ignition on. You've got another problem that you'll have to run.

Interesting thing about these coils is that they're dual-fire, meaning when since one coil runs 2 cylinders, both cylinders get a spark when it fires; 1 gets it on the top of the compression stroke, the other cylinder gets a wasted spark. So if you lose 1 cylinder and teh other continues to fire, the coil is doing what it's supposed to do. Trouble shooting at that point would lead me to the plug wires. But when you dry hung the new coil and it didn't work, and then the original one didn't, utp is right in saying to check the crank trigger (sending unit) and ECU. Something electrical is going on that's limiting the amount of power you're getting to the coil, when it's triggered it's not throwing enough juice to get a nice fat spark in teh cylinder.

 

[Bobbychet]

Also
when you post this problem in the right forum.
include what cylinders aren't firing.
that'll help us narrow down possible faulty
wiring.
Bobbychet

 

[mrbeetham]

Pretty sure they still had a solid state ECU in '89. Is your bike the oil cooled GSX-R? You might want to post in that section. Lots of guys that know a lot about those model bikes!

It may have been registered under the wrong year or something like that at some stage, but its deffinately water cooled.

Interesting thing about these coils is that they're dual-fire........ So if you lose 1 cylinder and teh other continues to fire, the coil is doing what it's supposed to do.

That is interesting, wish id known that before i ran off and bought a new coil. The silver lining is that Im probably still stuck with the initial problem, rather that being hit with a second problem so soon.

Also include what cylinders aren't firing.

Its just cylinders 1 and 4, so both cylinders that get their spark from the left hand ignition coil.

Ill continue going through and checking all my connections, as well as the sending unit. Fingers crossed its one of these. Am i right in thinking that its impossible for me to check the ECU myself?? Other than by deduction of course.

Cheers for the help guys.

 

[Bobbychet]

I think that's what one coil uses(fires)
correct me guys if I'm wrong.
It's 1 & 4 from one coil
and 2 & 3 from the other
you could swap coils and
see if 2 & 3 don't fire
then you'd know if it was a bad coil.
Bobbychet

 

[RoamingBison]

I think that's what one coil uses(fires)
correct me guys if I'm wrong.
It's 1 & 4 from one coil
and 2 & 3 from the other
you could swap coils and
see if 2 & 3 don't fire
then you'd know if it was a bad coil.
Bobbychet

Correct you are, Bobbychet. That would be the easiest bit of troubleshooting to carry out.

 

[mrbeetham]

I cleaned and checked all my contacts (all look good), checked out my sending unit, which also looks fine. Not really sure what can go wrong with a sending unit, but it was nice and clean and all the solder joints were strong.

I quite liked Bobbychets idea. When i was ordering my replacement coil the guy asked if i wanted a left or right coil. This gave me the impression they were different in some way. They are identical on the outside though, and do exactly the same job so i see no reason why it shouldnt work.

So, I swapped my working coil and my "unsure if its working" coil. Now i get no spark on any cylinder. Everything i thouch is breaking down.......... Now Im too depressed to swap them back and re test them. :banghead

 

[mrbeetham]

Once if finished sulking i swapped my coils back to how they were when i was getting spark to 2 cylinders. Still no spark to any cylinder.

Both coils are getting ~12.5 volts when the key is in the on position, but neither coil is giving any spark to a spark plug. This got me thinking. Whenever i mount a coil it stops working, could it be that i am mounting them incorrectly? The coils mount, from metalic bits that seem to come from inside the coil, onto a bracket, which then bolts onto the frame. Is this intended to ground the coils? Or should they be insulated from the frame??

I am 99% sure that i remounted them exactly how they were, but am really hoping its something this simple.

 

[utp216]

The only different between the two coils is the length of the plug wires attached to each. The coils themselves are the same part. So you have 12V at each coil when the key is ON? Wierd.. I think you have a problem with your computer. The computer completes the circuit on these bikes by turning "on" the ground side of the coil. If you have 12V at each coil at least you know that side of the connection is working.

I would trace the two wire connection from the crank trigger back to where it connects with the harness and also check those two wires were it connects to the computer. I think you use an ohm meter to check continuity. I would mount your testing gear and crank the starter over to see if the trigger is outputting the correct rating while it is turning on the end of the crank and passing the contacts on the sensor.

I think it's your computer to be honest with ya.

 

[RoamingBison]

Or a chronic problem with these machines: weak or faulty grounding points.

 

[fireforeffect49]

Or a chronic problem with these machines: weak or faulty grounding points.

Oh yes. Nomination for understatement of the year. :hammer

If you're getting a reading of 12v at the positive side of the coil w/ the ignition on, then that's good. Next step is to see if the crank trigger is "triggering" the negative side, need to run a resistance check from the negative coil lead to the crank trigger lead and see if it's grounded out somewhere. If both coils are now not firing off, then I'd say you've narrowed it down considerably. Could be a bad or corroded connection at a junction plug, could be the wire itself coming off the crank sensor. But I'd say your problem is now narrowed to that area.

Or the ECU. When in doubt, always blame it on the ECU. They're small, hard to understand, and you can't tinker w/ them. Plug-n-play idiocy and I hate them. I like my HD much better in that respect since my crank sensor is wired (read 1 wire from point to point) to the coil. Taht's it, there ain't no more.

But the wiring on the W/Cs is notoriously bad for grounding issues. It's got a common ground which is a complete pain in the ass. If the common ground fails, multiple systems fail and trouble shooting at that point is like scrubbing your balls w/ a cheese grater.

 

[RoamingBison]

If the common ground fails, multiple systems fail and trouble shooting at that point is like scrubbing your balls w/ a cheese grater.

Oh yeah, baby, I feel that! :scared

 

[utp216]

Get a Dyna 2000 and a set of Dyna mini coils. Problem solved! :thumbup

 

[mrbeetham]

I have some embarassing news....... The reason I was getting no spark at either coil was because, after i checked the trigger wires for continuity i forgot to reconnect them......... :hammer

I conneted them back up and retested the "bad" coil on the "good" side and it gives spark, but the "good" coil on the "bad" side doesnt. So its definately not a coil problem.

Heres a quick run down of all the measurements ive taken so far:

1. Both coils get 12.3 volts to their positive side when the key is turned on. They also both have 12.3 volts to their negative sides, is this correct?

2. Trigger puts out 0.6 volts on each side when cranked.

3. Checked for continuity between trigger and coils, both sides the same.

4. Checked resistance between negative terminal of coils and ground, both sides the same.

Both sides seem to be identical, yet one doesnt work. Its not the HT leads or plugs either, ive tried swapping them around.

Im with utp216, must be the stinking computer. Sadly im a student, and i only have about $10 spending money a week. At that rate it will take me 14 years to save up for a Dyna 2000. :sad

 

[RoamingBison]

It would be helpful if we knew the year and model bike. Some of us could keep an eye open for a used ECU. I picked up a used one for a 1995 1100 a few weeks ago on eBay for $30.

 

[fireforeffect49]

Reading on the negative side w/ the ignition on should be zero. Only time current goes thru the negative side from the trigger to the coil is to fire the coil. So unless your crank trigger is sitting directly over a sensor and not moving, you won't get a reading from the negative side. I'm not sure that's your problem, sounds like you may have put th eleads on teh wrong side of the coil?

 

[mrbeetham]

Hi guys, I have a bit of an update on my situation.

I found a method for testing my ignition, which involves attaching a 12 volt lamp between the negative side of my coil and the ground wire. When the engine is cranked this light should flash on and off as the CDI grounds and ungrounds the coil, so as to induce spark.

I tried this out and got a flashing light on my "good" side, but the light just remained on when attached to the coil on my "bad" side. This means either the CDI is not working properly, or that it is not getting the correct signal from the pickup coils.

Before i splashed out on a replacement CDI I checked the resistance on my pickup coil windings (this is something i didnt know how to do earlier). I have about 290 ohms on one of the windings and 2050 ohms on the other. I believe spec is round 300ohms so it looks like my problem is my pickup coils after all.

Does anyone know of any other tests I can use on my pickups, or of any potential remedies for the situation aside from new pickups???

Id also like to thank you all for the help you have given me so far, I know my way round an ignition system backwards now, but would probably still be back at square one if it werent for you guys.

Cheers