Ignition Systems Are Serious Business

[sh@un]

With RB coil packs, the iron-core stack's black coating always ends up coming off / wearing away to some degree (under the bolt heads esp., plus eventually some is always pulled away by the mounting brackets when you remove the coils). Obviously this leads to a direct conductive contact with the aluminium bracket frame, and in turn all the rest of the coil packs. Does anyone know weather this can somehow reduce the strength of the coil, and/or contribute to misfire?, perhaps by encouraging a short to earth?

[89CAL]

Pretty sure the mounting bracket is insulated from the coil itself so there is no issue with that.

[sh@un]

when that black coating comes off, the core ring metal comes directly in contact with the bare surface of the single-piece aluminum bracket; either on the underside, or by a conduction path down the bolt itself into the bracket thread.

where's the insulation?

[beemae30]

I dont think its an issue. Research how a coil pack works. I don't really think 0.1mm of paint is going to insulate 5,000 volts. My coil packs have nearly no paint on them and its been fine for 30,000kms.

[sh@un]

[edit: dbl post]

[sh@un]

I understand how they work, and I'm pretty sure the voltage in the secondary winding is higher than that

but weird things do happen- in that pic, you can see the lighter discoloured section on the side of the coil pack where an arc has been jumping to the bracket rail that runs along the side of the coil. both the coils (all of them) and the rail end up with carbon marks from that.

I've taped the replacement coils and the bracket rails on both sides to try and increase the resistance to spark-over between them, but it still hasn't completely eliminated the (fairly) occasional misfire

where the heck is the spark energy escaping to?

[MrStabby]

Pretty sure the mounting bracket is insulated from the coil itself so there is no issue with that.

Correct. The metal core is not connected to either of the solenoids inside (unless its stuffed), so it wont be carrying any current, so it doesnt matter if its got paint on it or not. A thin layer of paint wouldnt be effective against high tension anyway.

EDIT: actually if the core was grounded against the mounting braket then it might well be an attractive place for the current to go.

Whatever - just insulate the best you can where its arcing.

[beemae30]

Your coil pack is probably buggered, There could be alot of other reasons for the miss as well. And as MrStabby and i both said paint would not be able to stop the current if your coil was earthing threw the mounting frame.

[sh@un]

I guess the next thing to try is to find some very thin plastic washers to go between the coil and brackets, plus underneath the split washers of the bolts

[sh@un]

Your coil pack is probably buggered

these ones don't have the external signs of that kind of shorting, but obviously that's not to say they are tip-top

the annoying thing is you can hear a spark jumping to earth at idle every few seconds, but with the coil-cover off and in the dark, I still can't see where it's going to

[89CAL]

I have never cut one open.

But they will be insulated internally. The bracket on the outside will be part of the insulation and therefore not pass a current from the coil to the bracket.

Simple fact is, as said, a thin layer of paint would not stop 10,000+V from jumping from the coil pack to the bracket in the first place, and I dont think they would have designed it like this

There is an earth cable that bolts to one of the rear bolts that holds the bracket down, this may be there to drain any voltage that does manage to escape to the bracket.

[sh@un]

you can see the insulation- all that injected resin that encases the windings around the bakelite(?) sheath that the core runs through.

haven't seen the earth cable you mention on mine (S2 type RB25 with the igniter built into the coil pack), but I'll have a good look back there tomoz.

maybe someone didn't reconnect it ages ago and I've failed to notice it. fairly sure not, but I'll check either way

[MrStabby]

I guess the next thing to try is to find some very thin plastic washers to go between the coil and brackets, plus underneath the split washers of the bolts

I dont think that's going to help. Have you gone crazy with electrical tape/silicon/sikaflex/whatever to get some insulation into the air gap where the arcing is occurring?

If there is a problem with arcing to the core, putting plastic washers will just make it arc to the bracket instead IF they are effective in insulating the core from the bracket, which I doubt.

I think the fundamental problem is the breakdown of the insulation around the solenoids. The core to bracket is a side issue.

Might be worth checking the solenoids with a multimeter. If they're not within spec, then you'd be better off with new coils, because you cant fix that. If they're ok then persist with the insulation.

[sh@un]

ok, sweet

what should I set the multimeter range to, and which pins on the coil plug do I test and what sort of readings should come back?

[mad082]

the temps might be a bit of an issue, but you could try wrapping the coils in a feather weight bike tube (0.6mm thick rubber). that would certainly stop any arcing from the main body to the bracket or rocker cover, but won't stop any internal arcing that is then being grounded through the bolts.

[sh@un]

I've already bombed the coils and the bracket rails with 100mph cloth tape, which did help somewhat

[MrStabby]

ok, sweet

what should I set the multimeter range to, and which pins on the coil plug do I test and what sort of readings should come back?

Dunno. On the previous generation coilpacks primary winding (where the power is switched in) its 0.6 to 0.9 ohms, middle and left pin when looking at coil plug. Yours will be different - i'm guessing you might not be able to check the primary winding unless you can power up the ignitor..... hmm mightn't be worth the trouble unless you can find the proper check procedure out of the workshop manual. The insulation fix is cheap so maybe just get that sorted and see how the coils go.

[MrStabby]

I've already bombed the coils and the bracket rails with 100mph cloth tape, which did help somewhat

Unless you can confirm it insulates electrically, rip it off and use a branded electrical tape. I've bought Nitto branded japanese made tape from Jaycar. Good stuff.

[sh@un]

Nitto eh? I'll look out for it. Cheers

I'll check the impedance of these and see what results either way.