TESTING COILS ON A TWIN SPARK

[the smudger]

I suspect this is already on here some where but...

If you have a high speed misfire, or stutter, and suspect a stick coil here's a nice easy way to test..

Run the engine till warm. Be VERY CAREFUL in the next few steps, as the exhaust will obviously be hot!!

Expose the connections to both the primary (main) and secondary (underneath) coils (small black connectors).

Familiarise yourself with the small electrical connecter on the coil, i.e. how to unplug it easily. At first it can be tricky, but like anything once sussed its easy.DONT PULL THE STICK COIL OUT!!!! THE CONNECTOR YOU ARE PULLING IS A 12v SWITCH ONLY, NO CHANCE OF A SHOCK FROM THIS BUT IF YOU PULL IT OUT YOU WILL GET A SHOCK!

With the engine running at idle, disconnect the secondary (the one underneath).

If the engine stops straight away, the primary coil on that side is goosed.

To explain this, the secondary coil fires if the exhaust emissions are high, to sort of clean them up. If the primary fails, the engine control unit will notice a higher than usual HC reading at the O2 sensor, and fire the secondary. It will do this continually, hence the reason why most coil failures are not easy to spot as the engine controller just takes over!

The secondarys are fired up to 60 degrees past TDC hence the reason why the 'stutter' occurs at high RPM, the engine speed almost makes it impossible for the engine management system to catch up!

Hope this helps someone?

Rgds

Steve.

[ianbcr]

nice one Steve, something for Masha to try.

[metropolis2k]

Thanks for posting! I knew about this and had seen Steptoe do it on my bike but couldn't for the life of me find it written down anywhere.

[Droptarotter]

Nice report Steve.
So how would you test to see if the secondary coil is faulty? Or is this not necessary??

Cheers

[the smudger]

Nice report Steve.
So how would you test to see if the secondary coil is faulty? Or is this not necessary??

Cheers

Unfortunately not so easy.....

The only concrete way of telling is reading a fault code. If the O2 sensor reads high HC's, the engine ECU would normally fire the secondarys, which in turn should reduce HC's in the exhaust gas, which the O2 sensor would pick up, thereby enabling the engine ECU to switch off the secondarys.

In the real world, the secondary coils fire more often than not, as the emissions are high on these engines, so if the HC's are continuously high due to the fact the secondarys are not working, a fault code will be logged.

This I believe is the only surefire way of testing the secondary coils, although its worth bearing in mind that its generally heat that destroys coils, and the secondary coil, because of its shape and position generally runs much cooler, therefore would not fail as much as the primary which is buried in the head.

Rgds,

Steve.

[Droptarotter]

Nice explanation Steve, thank you very much!
Cheers

[masha]

Thanks Yes - I will be trying this - that is helpful - thanks V. Much.

Masha

[masha]

The only thing is for me - no codes indicating high O2 readings present - so this would point to it not being my primary coil?

[Steptoe]

[The only concrete way of telling is reading a fault code.
so if the HC's are continuously high due to the fact the secondarys are not working, a fault code will be logged.

.

Coil fault codes aren't logged.

[masha]

Thanks for that - I gave up with mine and left it with local independent BMW mechanic to look at - no news yet - I expect he will simply replace all coil-related packs and sticks to resolve - I'll chase next week but have just got back for a lengthy tour on my R1150GSA so Cup bike has taken a bit of a back seat, and I'm even thinking of changing it for a Duc Hypermotard when I get it back, unless I fall in love with it all over again when I pick it up from repair. I've been after and HP2 sport to replace it with, but its proving tricky to get one, but something will turn up and the 1100S be back on the road again soon I expect.

[Neil178]

There are a few HP2 sports for sale. They are coming in over 14K. Having asked around I was surprised to hear one at 17K. Too many collectors and not enough riders. I can't see myself paying more than 9K for one which is why I'm about to add to the stable with a S1000RR. The force of the dark side is strong . . . . . .

[Neil178]

Well off thread sorry chaps! Just spotted a hp2 sport, six miles only.
Asking £24,990.
Lost for words!

[dave the german]

That really is taking the pi$$ - just my opinion - and I do think they are a stunning bike but......

[metropolis2k]

Just bumping this to the top as it's so useful.

I was on the BCR at the weekend and it felt like it was down on power. Then under heavy load the power delivery became really uneven (like surging at really high revs) and it started backfiring a lot. It all pointed towards the coils so I did this test as I'd seen Steptoe do it before.

Pulling a secondary lead and comparing showed that one side made no difference (so the coil stick on that side was fine) and the other side caused it to immediately run on one cylinder (so the coil stick on that side was doing nothing). Time for a new one!