Questionhi barrie i know this is not an mg but lucas wiring all the same. jag mounted the coil just in front of rocker cover which i thought was wrong because when i put my hand on it it was really hot and engine misfired until it finally cut out. i took coil off and sat it on the wing, left the car running for an hour with no missfiring running perfect. put coil back in front of rocker cover and after a few minutes it began missfiring again. got new coil and fitted it to the valance away from rocker cover. car ran good, but after 10 miles it began missfiring again and eventually cut out due to overheating coil. this car is positive earth and i was wondering was the original coil the wrong one. any assistance would be appreciated ciaran.
AnswerHi Ciaran. Wiring the correct coil the wrong way round usually allows a car to start and tick over ok, but it will be down on power and hesitant to pick up from stationary.
First, check the base of the coil looking for a voltage. I have seen some with 6V stamped on the base. Yours should say 12V. You can often tell the age of a Lucas coil by looking for a date stamp. If it says 2365, then it was made in week 23 of 1965.
If you have an ohm meter, check the resistance of the coil. It should be between 3 and 4 ohms. If it is around 2 ohms, then you have an 8 volt coil that is designed for a ballast resistor. If it is less than 1 ohm then the coil is intended for a modern electronic ignition system.
The original coil would have had the letters SW and CB on the low tension connectors. CB must go to the contact breaker, and SW to the power supply. On a more modern coil, they will be marked plus and minus. For positive earth, connect the contact breaker wire to the plus side.
Which way up is the coil? It should be mounted with the HT terminal at the top. Some coils are partially oil filled, and they overheat if inverted because the internal components will be in an air bubble instead of being cooled by the oil.
I hope this helps
