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?

Get a better battery and try before pulling carb. Coukd be a bad earth even but if fires ok with a jump id try battery.
I disconnect mine as I had issues with it draining over a week.

Whenever it is a cold start problem, it is almost always the choke setting.

But first, check the sight glass. It it is empty, the fuel leak is causing the problem.

Sight glass level is slightly above the dot in the middle

Just like metallica sang.... battery!!!!

Battery? If the engine cranks, its not a battery problem. Adjust the Choke.

He says he jump starts it due to not cranking properly and it starts. Plays up once its colder. Symptoms of bad battery too.

I have tried partially and fully closed chokes but they dont seem to help :(

Replace the battery.

You guys sure nothing else about the carb is suspected?