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Old 07-20-2011, 12:56 PM   #26
TheRepairMan
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Join Date: Nov 2005
Location: Bluff City, Tennessee
Posts: 4,094
Quote:
Originally Posted by TJ 351 View Post
...Those coils seem to have strange troubles.
...
Note the IMPORTANT UPDATE half way down this post. Something to consider first when troubleshooting your ignition coils.

I wouldn't call it "strange". This is fairly common in lots of vehicles with COP "Coil On Plug" ignition systems these days. Circuits in these coils seem to rarely indicate any problem, but the insulation properties of the coil bodies leave a lot to be desired over time.

So here's an autopsy of the mysterious misfire.

The high voltage secondary current always takes the least path of resistance, and once the insulation goes through its life cycle of heating and cooling so many times it eventually becomes the weak link providing some extra path for some or all the energy to escape. We are talking HIGH voltage here!

Remember the basics, an ignition coil is an electrical transformer consisting of two different sets of windings. It converts small voltage being input, into a large magnetic field in the second winding. When the primary coil is triggered or grounded, and the magnetic field collapses, a large electric charge is generated from the secondary winding to fire across the gap of a spark plug. That same spark is met by variable resistance in jumping that gap depending upon conditions, or "load" within the combustion chamber.

The problem generally starts out as a very small secondary voltage leak to ground through a heat crack in the body of the ignition coil that's not suppose to be there. Often the very first symptoms are an intermittent misfire that may go away at higher RPM's or when the throttle is reduced. This occurs when a coil is first beginning to break down, but refuses to identify itself, leaving a multiple choice answer to be solved.

Which cylinder is affected? With the coils tucked away so neatly on our bikes that can be a fairly difficult, and time consuming question to answer. Since the coil in question may still be firing most of the time, comparing the temperature of each exhaust pipe, while being a very valid and easy test, may or may not be 100% conclusive, and since our bikes are not OBDII compliant, they don't have the capability of telling us which cylinder is not getting the job done. In Mikee8382's case, he was pretty fortunate to have noticed the small whitish burnt through spot on his bike's coil #3. That's obviously the best case scenario.


The service manual, on pages 8-91, 8-92 tell you exactly how to test the coil's circuits, and how to check for spark, but they completely ignore the most obvious test to me based on the majority of failure causes. Stressing the coil's insulation under load. And, about the only way to prove the spark is taking an undesired path to ground is to recreate similar electrical load conditions in the shop. The bike WILL NOT be running during this testing!

!!! Exercise CAUTION here. Do not proceed unless you are confident you understand what you are doing. Seek professional help for ereticutions lasting longer than four hours!

First, access all the coils, and loosen each one so they can be carefully and gently pulled up and away slowly from their individual spark plugs. You are going to test each one, one at a time, while performing the "Actuator operations, test numbers 30 through 33". This is done while firing the corresponding ignition coil using the on board diagnostics to inspect and visually witness a suspect voltage leak (high voltage spark) off the side of a faulty coil insulator to the spark plug well tube. Read on.

This probably wasn't gone into depth in the manual because it can be a dangerous test to complete, especially if the stray spark decides to hit your hand during testing. Even experienced technicians shy away from bare handing a live coil. The spark may not kill you, but the rapid manner in which you might remove your hand from the source of pain can cause a lot of coincidental damage.

If you so choose, the Actuator operation table in the service manual is on pages 8-47 and 8-48, and the procedure to enter the Diagnostic/Sensor and Actuator mode starts on page 8-40.

Again, be CAREFUL testing any ignition coil while it is operational. The secondary circuit can typically produce as high as 35,000 to 40,000 volts when pushed, and YOU don't want to become the ground! Trust me! Also, be sure you have cleared the area of any combustibles before running any on-board diagnostics ...especially gasoline in or around your bike! The manual does instruct you to disconnect the electrical connector on the fuel pump first! You don't necessarily have to disconnect the fuel lines, though. I wouldn't unless I am taking the tank off and away from the work area.

And, on a final note ...once in a while you may not find anything wrong with a defective coil. It may pass all the tests you can throw at it, but replacing it cures the misfire. In this case, we can only speculate the coil insulation has broken down internally, or there is a intermittent open or short hidden within the coil. It happens!

Don't forget to change those spark plugs while you're in there. The old ones "may" have contributed to the coil, or coils breaking down in the first place.

IMPORTANT UPDATE!

BLAQHAWK, a member here, has brought forth that his experience was somewhat different wiith the ignition coil failures. Even thought the symptoms may have been similar, here's what he found...

That by simply unplugging the primary, low voltage side connector of the ignition coil, adding a little dielectric grease for good measure, and re-connecting the connection that his coils began working again. Although, I think the dielectric grease was of little consequence here, he has most certainly stumbled upon a possible legitimate problem as well as corrected it with this simple action. It's surely worth a try to anyone experiencing any suspected electrical problems. Disconnect and reconnect the connectors several times then retest the operation.

Now, here is the electronics side of my take on this... and keep in mind Dielectric Grease is exactly what its name infers... It is an electrical flow stop or blocker! It has strong insulating, lubricating, and element protection properties! It is more closely related to electrical tape in what it was designed to do.

Dielectric grease was developed to help lubricate and waterproof a connector but not to enhance the flow of electrical current! It is fully non-conductive, and should be used only to seal out moisture to help prevent contact and terminal corrosion. Therefore, it's not advisable to apply dielectric grease directly to the metal contact surfaces of the terminals themselves. It can actually inhibit electrical connectivity between low contact pressure connector terminals.

So, in the example BLAQHAWK has presented the more likely problem is one in which these very small primary connectors have developed high resistance from oxidation between the metal surfaces of the low contact pressure style terminals due to exposure to the heat, vibration, the elements, and what is known as Electronic Corrosion.

It's fully reasonable that by simply disconnecting and reconnecting the terminals to their counterparts that good solid connections were re-established. By applying a small amount of dielectric grease during this operation you may indeed help prevent the return of this often non visible corrosion from setting up again anytime soon.

Electronics stores sell a compound specifically for these types of connectors in the form of an Electrically Conductive Grease that was developed to enhance and lower electrical resistance across connecting terminals. It has to be used very cautiously as an application of too much of it might in effect create a metallic bridge across adjacent terminals in a connector that are normally isolated, and insulated from each other.

See electrically conductive grease here...

http://www.2spi.com/catalog/vac/silv...d-grease.shtml


-Roger
__________________


Dielectric grease information, IMPORTANT! http://www.yamahafz1oa.com/forum/sho...3&postcount=42

Ignition coil information, FYI. http://www.yamahafz1oa.com/forum/sho...0&postcount=26

Last edited by TheRepairMan; 04-07-2013 at 07:11 PM.
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