I will probably get in a lot of trouble for what I am about to say.... but what the heck,, we have a delete feature on this forum....LOL....
Has anyone considered simplyfying the glow plug system ? I mean hooking up wires to the battery, a normally off, push on switch, a horn relay, and directly to the glow plugs... just bypass all this timing etc stuff?
Anyone old enough to remember when cars had MANUAL chokes? You just pull it when you want to start the car,,,, and push it off after the car is warmed up a little... then they put in bimetallic springs which were supposed to do that same job... but they would slowly become less effective and you had wasted all sorts of gas before you actually noticed that it was not completely opening the choke even after then engine was hot.
On old cars I do not see anything wrong with simplyfying the mechanism. Can you (generic) hold your finger on the button for 15 to 60 seconds, then try the starter... ? why would we need a timer for these just to potentially give us problems at a time we don't need it....braced for the reaction.... Greg