Ignition Coil

[CapeLandy]

Hi All

Ser III 2,25 P 1973

I started having intermittent jerking while driving so I checked the following:
1. Fuel Filter OK
2. Carburetor cleaned out OK
3. Changed Condenser.
Then I found the points gap was closed. Fitted new points and was fine for 5km’s an then started stuttering again. Removed points and checked closely. Found red plastic melted such that the spring steel had melted into the plastic and closed the gap again.

Can I assume my ignition coil is causing too high a temperature in the points/spark?
I did note a dent in the top of the coil and it looks about 30 years old as well.
Any ideas?

Thanks

James

[JDNSW]

It certainly sounds as if the points are getting too hot, and yes, the coil is one possibility, although the dent and the age are not likely to be the problem - coil failure due to age or damage is more likely to show up as insulation breakdown or open circuit, neither of which would cause points problems. If it is the coil, it will be because the coil is the wrong one, one designed for use with a ballast resistor or possibly a 6v one. In this case the coil will be getting hot as well.

Other causes of overheating points include a faulty condenser (has happened with new ones!), points contaminated with oil, or, most likely, a bad or loose connection to the points set. Another possibility is excessive voltage from the alternator due to a regulator fault or possibly engine/chassis earth fault, but you would expect blown bulbs with that as well if driving at night (although the voltage might be lower with headlights on).

John

[CapeLandy]

Thanks Mate

It started happening with old condenser so new one made no difference.

Earth is fine as well as voltage.

The Coil is pretty warm once motor is shut down. I will change it anyways if I find someone open on a Sunday.:(

Cheers
James

[JDNSW]

Thanks Mate

1. It started happening with old condenser so new one made no difference.

2. Earth is fine as well as voltage.

The Coil is pretty warm once motor is shut down. I will change it anyways if I find someone open on a Sunday.:(

Cheers
James

1. Note my comment about faulty new condensers!

2. If the battery is earthed to the chassis, and the alternator to the engine, it is possible to have a high voltage between the battery positive and the engine (but not the chassis) if there is a high resistance between the engine and chassis. Should cause starting problems though.

While it could be the coil, my guess is a faulty connection on the points, or possibly oil contamination. But replacing the coil, if that fixes it, shows it was the coil (except presumably you have changed the points, and if it was a bad connection there you may have fixed it!).

John

John

[rick130]

Ditto what John said, particularly regarding condensers.

I'd suspect poor alignment of the contacts on the points creating too much resistance.
Also, try to set the gap by dwell rather than a fixed gap figure. I always did this and usually ended up with a reduced gap, but you get the maximum coil saturation time, and that should reduce the load on the points too.

[CapeLandy]

The new coil is in and also removed the piece between the inside and outside of the distributer and ran a direct wire from HT coil to points connection and all seems well so far.
As soon as the rain clears, off for a test. Too manyu leaks on my head to go out just now.
Thanks for advice.
James

[Aaron IIA]

You have replaced the coil, so it doesn't really matter, but how much current was the old coil using? Hook up the positive and negative terminals to a car battery and measure the current. I am curious to find out the value. How does this compare to the new coil?
Aaron.

[CapeLandy]

I measured the internal resistance of the coil between all three terminals and did get different readings comparing the two coils.
The new coil uses 1,6 amps current but I did not measure the old unfortunately.
All tests confirm she is running fine now and I even got to work on time.:p
Another week:(
Thanks
James