This started a couple weekends ago when I was out of a cruise. My Spitfire
1500, with twin HS4s, was working fine until I stopped for lunch and went
to start it again. Car started running like it was running on 3 cylinders.
I checked and found the plug wire to #3 not clicking onto the spark
Check the spark plug for #3, and the distributor cap.
If your test produced a spark on the other 3 cylinders, something is wrong
in the #3 circuit.
Could be the plug lost its electrode.
Try replacing the plug first, then the dist cap.
Clark
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Spitfires
Are you sure there's no spark only on that cylinder?
Check the points gap too.
Try it on different dist cam lobes, see if it changes.
If the distributor is worn and the shaft wobbles it could be worse on that
one cylinder perhaps.
I solved my worn distributor by installing the crane/Allison solid
