ok, my car was missing then stopped, took it in to get fixed and found that a plug had come off the bottom of the coil. Easy fix and off and running. now it has started missing again so I went to see if the switch was tight and I got an electric shock or pulse from the bottom of the coil. Is this normal? its a 95 rover spi
thanks

The coil is essentially a step-up transformer. The plugs on the side are the power in (12V and ground) and the power out to the dizzy is several thousand volts.

So yeah, you can expect a shock from the plugs, but probably not a huge one at 12 volts. The output to the dizzy is usually above 10,000 volts, I think (can be over 30,000 for performance dizzys), so if you got that, you'd know about it (not dangerous because of the low current, but it certainly gives a kick).

By checking if the 'switch was tight,' do you just mean the plugs to the coil?

so you brushed your hand against the bottom of the coil? nowhere near the spark plug leads?

if so, then no, that's not normal.... or shouldn't be - your sparks would be escaping

It can happen if the coil is dirty, or the weather is especially humid. The spark tracks along the surface of the coil. The same thing can happen if you have dirty spark plug leads.

Tim

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1951 Morris Commercial J Type Van
1955 BSA C11G
1961 Morris Mini Traveller
1969 Triumph TR6R
1977 Leyland Moke Californian

i got a great shock from a plug lead once while running the engine to see which plug was miss-firing, made my finger numb for an hour or so

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Yeah, its easier for the spark to find its way to earth through a relatively conductive human than it is to arc across the air gap in the end of the spark plug.

Tim

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1951 Morris Commercial J Type Van
1955 BSA C11G
1961 Morris Mini Traveller
1969 Triumph TR6R
1977 Leyland Moke Californian

The shocks from a mini aren't very bad, the worst one i got was when i was fiddling around and accidently used my arm as an earth for the coil. The shocks from modern coil packs etc have a bit more kick. I think in the range of 70,000V or so, possibly more. Those ones make you twitch!

Some modern epoxy coils (like my Bosch GT40T, and many others) have the primary terminals on the bottom of the coil not the top. You can get a minor boot from touching these (when running) if there's a bad wire connection. You can even get a kick from the points themselves if you flick them open with ignition on. It's a result of back EMF.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I got a little zap at work the other week.
The tail of a powerline conductor I had hold off whipped around and caught me on my shoulder.
It's not pleasant being brought to the same potential as 22000volts AC.
Lucky the insulated EPV did it's job

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'72 English Van...'72 Export Moke ...63' 850...KZ 750E1...'74 P76

Do you work as a live linesman ?

Yeah, I've been a liney for a while now, but I've only been qualified to use the HV gloves since early this year.
The way the hand tools vibrate when you make contact with the live HV line still gives me a bit of a rush. I love it.
The heat's the worst thing though. Wearing thick rubber gloves and sleeves in summer has knobs on it.

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'72 English Van...'72 Export Moke ...63' 850...KZ 750E1...'74 P76

HV live line work is too scary for me. I have spent the last 21 years switching things off, earthing and issuing permits to work on stuff.