1970 XJ6 S1
I have inherited an XJ6 that is in need of everything. Current issue is an unstable tachometer indication. The car came equipped with an MSD 6AL ignition box and is trigged from a Lucas distributor utilizing points. I need to make a decision as to what to do next, i.e. look for a fix or ship the tach to an instrument repair shop.
The tach turns on with the ignition switch but jumps all over when revving the engine. This looks like an electrical component mismatch.
Does any one have experience with this ignition component sharing?

 

Do you have the " MSD Ignition Tach/Fuel Adapter" installed? Necessary to get Tach and EFI to work correctly?

MSD Ignition 8910 Part Number: 121-8910

MSD Ignition Tach Adapter Points and Amplifier Ignitions White Wire Triggered

Tach Adapter

• Points and Amplifier Ignitions
• White Wire Triggered

"If you are triggering an MSD Blaster, 5,6, or 7 Series Ignition with its white wire or points terminal, you will need this Tach Adapter. This unit will correct the operation of most voltage triggered tachometers or fuel injection systems that do not work directly off the tach output terminal of the MSD Ignition Unit."
Rgds
David