On all ten I work on none of these are wired up.they are connected when they are,to the starter solonoid.My text book lists them as a CAV designed mark 1 or 3 thermostat.And states "gravity fed adaptor,heater coil "Thing actually ignites fuel!What i have had with these is on three of them is compression loss due to valve clearances which was a pain cause local dealer would only supply shims in packs of 5.Even less help was the range of sizes.Had to resort to removing valves and shortening stem length on a snaped belt rebuild,laborius.Anyway all three starting problems were solved.If your equiped I'd try a compression leakage test.on mine this showed comp loss of 15-20% on holding pressure,could'nt get a feeler gauge into several exhaust tappets.Not suggesting same as your's as i never tried tow starting them as it scares the crap out of me .but worth a look.good luck
caine
August 2008