Frustrating year

[Graham Perry]

Its been one of those years, little motorsport, coz of F&M and car unreliability. I have just suffered my fourth breakdown of the year. Anyone who knows me could testify that I am seriously into keeping the car in tip-top condition, so I have concluded I must have upset the gods somewhere.

 

Driving in the middle of nowhere at the weekend, engine reaches 9300 and hits the soft cut out and then dies, so I coast to a halt. Drag it home behind my brothers car only to find the rotor arm had disintegrated. The rub is it was thoroughly checked in April for cracks. Its of the proper Lucas type and not the dodgy one that Caterham used to fit years ago , so its a mystery.

 

While checking this out we noticed another very weird problem that I would appreciate an opinion on. The coil had been arcing from its high tension terminal through the coil insulator and the end of the lead and was earthing on the low tension negative terminal which was also insulated. It had even burned a small hole through the Coil Insulation,the coil lead insulation, and the low tension insulation . This is no small distance - nearly 2cm's. Has anyone ever seen this before? My father has been a mechanic/garage owner his whole life and had never come across this level of destruction. The car though wasn't even missing a beat when this was happening. The leads were all seated properly and the wires and coil only about 8 months old ? The ignition is Emerald 3D (Carbs) and the coil used has the recomended resistance of 1 ohm. Could it be the coil is of too high a capacity for the system ? Any ideas ?

[Lennie]

Graham

The reason for arching is that the rotor was moving on the distributor spindle and hence was not alligned with the segment on the distributor cap. This meant the spark had to jump an excessive gap. The car would not miss as you were actually getting a huge spark [up to 40Kv]but it would not last for very long [the spark time].Eventually it is easier for the spark to earth through the low tension terminal than jump the gap.

[Graham Perry]

Len, Thanks for the explanation, it ties in with what my father finally came up with by way of a theory after a week of thinking about it (he says hes not as young as he was). He finally remembered he had seen this on a mark 2 Cortina in the 70's (I didn't push him for an exact date or he would have gone off to dig out the invoice to the customer!)

 

I am still amazed though that it could jump through three seperate layers of insulation. It gives you a lot more respect for all things electrical !