Running On 2 Cylinders, Help

[snowgear]

The 1970 Elan S4 Se was running great on a 50 mile run, then after a stop at the Library, I limped it 1 mile home on 2 cylinders.. #1 & # 4 plug wires are not firing. I did the arc test,, Nothing on #1 ..It has Pertronix points, I checked all wires to the coil, cleaned cap, sanded lightly the #1  spark plugs. Those 2 plugs were lightly oil fouled.. The cap is scored a little on the contacts.. What next?? Any ideas??
I do have a New cap and rotor here.. Thanks, TIM M

[type26owner]

Hi Tim,
The Pertronix Ignitor is an all or nothing device so it's probably okay. Fouled spark plugs are actually electrically shorted to earth across the ceramic insulator due to carbon buildup. The entire insulator surface has to be sandblasted until all the carbon is removed to restore them. Try replacing them first. If it fires up on all four cylinders then you've got another problem to solve which is causing the fouling. Two likely things could be wrong with the spark plugs that would cause the fouling. There are others also since fouled spark plugs are an end-of-the-line symptom for many other root causes. If they are a resistor type then the internal resistor in the spark plug body might have failed by changing it's value up from the normal 5k ohms or just opened up completely therefore cutting off the spark altogether. New resistor spark plugs should have their resistance checked right out of the package. Not all that uncommon to have to find a new bad one. The other issue is the heat range. You might have too cold a spark plug for the amount of oil or fuel being burned in the combustion chamber. Got any blue or black or white smoke?

While on the subject of spark plugs there is a little known problem with spark plugs caused by the sharp edge of the electrode and the tang getting eroded away until they are blunted. Sharp edges provide what's called an edge-effect field potential that induces the spark to jump the airgap at a constantly lower voltage allowing the coil more time to saturate and is very beneficial. Racers go through plugs quickly because of this erosion. Lowering the electrical stresses on a Lucas ignition system is recommended to help prevent dielectric breakdown problems. You also want to increase the dwell as much as possible on a single coil ignition and the Ignitor does this very well with it's square wave signal which minimizes the delay.

If this does not fix it post that info back here and I'll talk you through the next step. How long has it been since you've done an ignition system tuneup from top to bottom?
-Keith