I know this is more of a general carburetor-engined issue but perhaps the lot of you Datsun owners can shed some info on this.

1981 B310 with the stock A12A motor and Hitachi DCG306 carb. In warm weather, 1-2 pumps of petrol will get the engine fired up no problem. In cold weather (especially overnight rain), the engine would crank but that's about it; no chugs no blips no nothing.

If I try to pump more petrol, one of two scenarios may occur:

1) The engine still doesnt respond
2) It splutters a little due to slight overflow/flooding.

When (1) happens, I'd still try cranking but nothing would happen. If I pump more petrol a third time (or fourth or fifth because the engine STILL doesnt respond) it would splutter tremendously due to excessive flooding, an indication that I might as well take the bus.

When (2) happens, I'd crank it a couple more times. Sometimes the engine would start, sometimes it wont. If I try pumping a little more, the spluttering continues in a never-ending cycle, or if I'm lucky it will start.

I'm pretty sure the problem lies somewhere in the carburetor, but my dad suspects the ignition coil isnt making enough voltage for the spark plugs.

But then again I do notice my battery is significantly weaker in colder weather and the cranking isnt as strong. When I give it a jump start the engine would start almost all the time. I seem to understand that the weaker battery would cause the following (please correct me if mistaken):

- Slower cranking leading to weaker compression in the cylinders; air/fuel mixture doesnt burn properly

- Less voltage going to the ignition coil and finally to the spark plug; weaker spark doesnt ignite the air/fuel mixture

So... your thoughts please?