mystery wire on engine block

[rmmchl]

does anyone what the wire is that connects to a bolted on valve of some type on the engine block just below the valve cover on the injection pump side and goes through the firewall---it goes through the same hole as the tach cable on the firewall.   It is small in diameter--------could it be the temp gauge wire?

[bpossel]

From your description, sounds like the temp gauge wire.
Bob

[Cees Klumper]

I would second that.

P.s. be very ginger with it - it's more aptly described as a 'capillary tube' and contains a gas. Once this gas is allowed to escape you will have to buy a whole new tube at a cost that is not insignificant.