Coil Shorting

Khryztal · Sep 7, 2009

Evening all.
Just been checking things over in the engine bay. I noticed while I was testing the sprak plugs etc that if I had 1 HT lead off the coil was shorting out. From the edge of the HT lead rubber cap and the coil earth point.
I would say the coil has had it. Any other thoughts on this?

Soloby Rob · Sep 7, 2009

Khryztal said:
Evening all.
Just been checking things over in the engine bay. I noticed while I was testing the sprak plugs etc that if I had 1 HT lead off the coil was shorting out. From the edge of the HT lead rubber cap and the coil earth point.
I would say the coil has had it. Any other thoughts on this?

Why the stuffing hell were you pulling plug leads off a running engine.

Khryztal · Sep 7, 2009

The engine wasnt running when I pulled the lead off. That hurts. Truct me on that. Had the lead off when I started the car.

Teflon · Sep 8, 2009

If you have energised the coil, then triggered it, but not got it connected to a spark plug........ that spark is gonna try and go somewhere, innit?
does suggest that that's the 'easiest' route to earth, so may be worth cleaning and attempting to insulate a bit better, but with the plug lead back on, the plug should give an easier route to ground for the juice.....

oggyv8 · Sep 8, 2009

I am having the same problem with the coil shorting out at the king lead and have replaced the rotor arm ,dizzy cap and all leads so next is the plugs because i was told if the plugs are fubar they arnt sparking right and the coil is trying to earth instead of spark being delivered to the plugs.

CharlesY · Sep 8, 2009

The spark is upwards of 25,000 volts for a short moment.

It is DESPERATE to reach earth.
It has no other ambition than that. That is all a spark can do.

Sparks are smart.

They head for earth the easiest way, AND when they do this they often cut a track on the surface over which the spark tracked, and that track (looks like a wiggly scratch) is an even easier route for the spark next time.

What you are trying to do is to make the SPARK PLUGS the easiest route the spark can find to earth. Don't let the gap get too big.

If you let the engine run AT ALL with a plug lead off then the spark that should have gone down that lead will be forced to find another route to earth, and in the process may cause troubles later. Burned track inside distributor cap, pinhole leak in a plug lead or KingLead, track burned on rotor, that sort of thing.

I'm sure there must be a moral in all this somewhere.

CharlesY

oggyv8 · Sep 10, 2009

Hello,replaced the plugs and drove 22 miles then the disco packed up !!! AA man came and i turned the key,there is the problem he said,your coil is fubar. Put a new coil on as the old one had a crack at the top and it was earthing to the radiator mount and no spark down the ht lead. A new coil has made a fantastic differance to how car runs so you may be best starting with a new coil.

CharlesY · Sep 10, 2009

oggyv8 said:
Hello,replaced the plugs and drove 22 miles then the disco packed up !!! AA man came and i turned the key,there is the problem he said,your coil is fubar. Put a new coil on as the old one had a crack at the top and it was earthing to the radiator mount and no spark down the ht lead. A new coil has made a fantastic differance to how car runs so you may be best starting with a new coil.

More than likely what you say was a CRACK on the top of the coil, was actually a surface TRACKING BURN caused by sparks being forced to take that route to earth instead of the proper route through the spark Plugs. This often happens because the engine is turned over on the key with one or more plug leads off.
CharlesY

tacr2man · Sep 11, 2009

What Charlesy has told you is spot on , its also why in 99% of cases what stops the V8 in water, the top of the coil shorts out , not dizzy etc as most people think .

Coil Shorting

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