Ignition coil plastic cover broken

[prwood]

Yeah, it's my second post in the past few days with "broken" in the subject. (It would be my third, except one of the things I broke I figured out a way around it and decided not to post). I probably need to take more frequent rest breaks, because the fatigue is making me clumsy.

Anyway, at some point, probably when levering the fuel injectors off of the manifold, I whacked the side of one of the ignition coils with the end of a wrench, and part of the plastic case around the side of the coil broke off. It's probably about a 1" x 1" piece. It looks to have exposed some of the outer windings of the coil. I didn't take a photo of it, sorry, but I circled on the stock photo below to show roughly where the plastic came off.

ignitioncoilmarked.jpg (98.95 KiB) Viewed 2751 times

I'm assuming that it's NOT okay to start the engine with the coil exposed like that?

Since I need to get the car back on the road, my thought was to cover this area with electrical tape or wrap the whole top of the coil in silicone tape in order to insulate the coil, and then order a replacement coil online and swap it in when it arrives. Would this be a safe solution for the short term?

Unfortunately I don't have another car; otherwise, I would just let this one sit until the replacement coil arrived.

[oragex]

Don't think it's safe indeed, especially since some electronic modules on this car are quite sensitive to any power surge. Not sure if several layers of electrical tape could prevent an electric arc between the coil and the engine cover, I'd certainly not risk it personally. I'd rather wait for used but original Volvo one from Ebay.

" A common automotive ignition coil can generate an output voltage on the order of 30,000 volts. This is a sufficient voltage to produce arcs which jump an air gap of an inch or more."

[abscate]

Ive run much worse on VAG cars. The engine cover is plastic so it isnt going to ground too well. I would skip the tape (useless, as noted above) put it back and see if it misfires. If not, replace

You can buy a tested good used one from some nice people in the Parts Forum too...to have around for such contingencies..

[prwood]

One opinion each way on whether it's ok to run with part of one coil exposed to air.

I did check the specs on the electrical tape and silicone tape I have, and they only insulate up to 3000v and 8000v, respectively. So that's out of the question.

I went ahead and ordered this coil on eBay and arranged rides to work for the remainder of the week:

http://www.ebay.com/itm/VOLVO-C70-S60-S ... 1437621404

Aside: What would happen if I disconnected the electrical connectors for the ignition coil and fuel injector for the cylinder in question, with the thinking being that this would prevent any voltage arcing from the broken coil? Would the engine start and run with four cylinders, with 20% less power? Or would it fail to start? Or would it run but cause systemic issues, as the engine is built assuming that a certain number of pistons will be turning the crankshaft? There is probably an obvious and dumb answer, but I'm not an automotive engineer, nor did I stay at a Holiday Inn Express.

[abscate]

The high voltage isnt present at the coil, its generated inside. If you a have a voltmeter you can proble exposed metal and see if it is generating a voltage (it will be a time dependent spike of voltage as the coil is fired, of course.

Are you just around town (ok to run on 4 cylinders, ignition and fuel both disconnected) or flat out on 128 to commute to work (not ok) ??

It will pop a P030x code if the coil or FIJ are disconnected of course.

[prwood]

The high voltage isnt present at the coil, its generated inside. If you a have a voltmeter you can proble exposed metal and see if it is generating a voltage (it will be a time dependent spike of voltage as the coil is fired, of course.

Are you just around town (ok to run on 4 cylinders, ignition and fuel both disconnected) or flat out on 128 to commute to work (not ok) ??

It will pop a P030x code if the coil or FIJ are disconnected of course.

Most of my daily driving doesn't require getting on the highway. I can and do commute and run errands on local roads going 40mph tops. That being said, I do have alternate transportation arranged, so I can probably just wait until the replacement coil arrives.

However, veering once again into theory and hypothesis...

Regarding the voltage, I do have a voltmeter, but it only reads up to 1000 DCV, so I'm not sure what would happen to it when exposed to 30k DCV. I just looked at this diagram (which from what I can see on the outside, looks to be how my coil is built, although the image is not Volvo-specific):



Source: http://www.troublecodes.net/pcodes/p0352/

From the look of what I'm seeing through the broken plastic, it looks like the exposed part is labeled "magnetic core" on that diagram (thin layers of grayish metal sandwiched on each other).* I did just read an article on ignition coils on Wikipedia:

https://en.wikipedia.org/wiki/Ignition_ ... principles

So I see that "The energy that is stored in the magnetic field of the core is the energy that is transferred to the spark plug." However, and this is where I'm weak on electrical concepts, I'm unclear on whether this implies that a voltage is present in the magnetic core, in the sense that having it exposed could lead to a high voltage current traveling out of the coil and onto the engine or other surrounding metallic components, rather than into the spark plug.

* Now that I think about it a bit more, it looks sort of like a transformer I installed in my house recently, and I guess it basically is a type of transformer, except the one I installed at home was stepping down voltage from 120 to 24, and the one in the car is stepping up from 12 to 30,000.

[abscate]

The voltage is created by the collapse of the magnetic field, following Maxwells Equation number 4 (I hope I got the order right). The core is just helping make the magnet a better magnet by putting some metal into the solenoid.

I can't say for certain that the coil has no voltage on it, but it won't be high voltage.

You really can put it on and see if you get clean running. It will either work or not. Ive had two or three coil failures and they are not dramatic.

[mrbrian200]

High temperature RTV. The black stuff. You primarily concern is to keep moisture from eventually working it's way into the windings which will usually result in weak or no spark. Seal it up before that condition develops and it's none the worse for were. Note black tape is not a permanent/dependable moisture seal.

[prwood]

Just remembered I took a photo of it when I got home tonight:

IMG_1216.JPG (745.94 KiB) Viewed 2616 times

So if I slather RTV over that area I should be all set?

[abscate]

That 3 mm of plastic is not high dielectric insulation of any kind, I think it's just protecting it from moisture and oil. RTV, tape, plastic bag,

If you do it at night you could see if there was any breakdown, like a bad plug wire , but I really doubt that would be the case