Low coil voltage on cranking

[shed driver]

1973 Rover P5B Coupe. It's had a new coil and fitted with electronic ignition. After its winter lay up it is proving a little difficult to start at times. I thought initially the original mechanical fuel pump may need overhauling or replacing with an electric pump. It turns out now that I've only got just over 6V at the coil when cranking, over 9V when it's running.

I assume I should try to get a switched 12V feed to the coil when I'm turning the key.

Is this difficult? Is it something a competent auto electrician should have no problem with?

SD.

[shed driver]

Cheers.

It's a new battery, 12.5V at rest and over 13V when running. The alternator was changed about 10 years ago (less than 10,000 miles ago). Headlights are bright and steady even when revving the car and idling.

I will check the earths when I get the car out of storage again.

SD.

[shed driver]

Thank you, very informative. It's a late model so "shouldn't" have a ballast, but so many previous owners have been enthusiastic with maintenance the wiring diagram is a prize winning work of fiction.

I replaced the coil with one that should have fitted. I may have to check everything in the entire circuit although with all the changes made over the years it may be time to recruit someone who knows what they are doing!

SD.