corrosion on coil ht terminal (pics added)

[andyzeetec]

Pulled the ht leads off the coil to find one of the sockets and the ht lead plug is corroded with a white oxide. Cleaned oxide off but coil socket is still brown and tarnished inside, Compared to the other socket which is gold. Any ideas on how to clean or why this has happened. May explain the starting problems.
Thanks

[andyzeetec]

Measured resistance and found primary was fine, but secondary high tension side was open circuit. New coil and leads ordered.