• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Small Spark at Ignition Points OK?

Share this page

martyc

martyc

Jedi Hopeful
Offline
Being an old-car-newbie, I have a silly question for the group...The TD was running really poorly and along with plugs, I just replaced the points and condenser. The old points were really badly pitted.

After gapping the points, I was setting the static timing and I noticed a small spark occurs across the points just as they are opening. Is this normal? I thought the condenser was supposed to suppress a spark across the point gap, but maybe a small spark is OK? That's the silly question.

Also, the new points and condenser seem to have fixed the problem and the car's running much better.

Thanks, in advance, for any input.

Cheers,
Marty /ubbthreads/images/graemlins/cheers.gif
 
Even a somewhat large spark across the points is normal. Not to worry. The condenser stores electricity because the current is intermittant to the points ( something to do with dc vs ac current). That way there is electricity there even is the main wire is not charged at the crucial moment of point contact.
 
Hi Marty,
The condenser allows the coils inductive magnetic field to collapse more quickly as the points open & absorbs the current that would normally arc across the points. This field collapse is what induces a current in the high voltage winding of the coil & causes the spark plug to spark.

If the condenser size (capacity) were perfectly matched to the coil inductance, there would be no spark at the points. With the manufacturing tolerances usually present, the condenser & coil are rarely perfectly matched. In theory, you can tell if the condenser is over or under capacity by observing which point has the hill & which has the crater. After you found out, you could measure a bunch of capacitors & find the perfect match. This is rarely or never worth the trouble.
D
 
Hi Marty, the answer to the "Silly Question" is yes a spark across the points is OK.---Keoke /ubbthreads/images/graemlins/laugh.gif
 
Aloha Marty,

That spark is also a quick test of your condenser. If the spark appears to be white or blueish, the condenser is good, if it is orange or red the condenser is not good.

Safety Fast,
Dave
 
Thanks for the responses. Based on your collective input, looks like I'm in good shape (at least the TD's ignition system is).

I'm off for a more extensive test drive this evening...

Thanks (again),
Marty /ubbthreads/images/graemlins/driving.gif
 
Marty,
I changed to a Pertronix in my TD as I had a wobble in the Dizzy...the points kept closing up. Have since had the Dizzy rebuilt by John twist but kept the Pertronixs....no more worry about points & condensers. Make sure you get the positive ground version if you do change
FWIW
 
Back
Top