If you've got a brake booster fitted....then it's a hole in the booster. Find a replacement.

I've seen this several times before. It plays even more havoc on EFI systems.

I like to quote "I know everything"

Chris

I dont think it will make a difference when you're adjusting the carb settings while your mate depressing the brake pedal

unless....

your mate will press the brake pedal while driving and you at the same time adjusting the carb setting, dont forget to strap yourself on the car real tight while doing this....

yea i got it goin now, jus played around with the idle and the mixture settings...

w00t now i actually have a choke... my choke wire was all ####ed at the end where it is at the carby and wasnt pulling at all, cut the tip and screwed back in and now i have a choke... w00t
no more waiting 10 mins to warm up the car

Some Datsun carbs have a dashpot stop for the curb idle speed (round bellows thing). But they also have a fast idle cam as well.

For testing, set the idle high (900 rpm). If it still dies, it's not the idle speed setting!

ahh, thanks guys, when my mate comes over i will start adjusting it then, get him to press the brake while i adjust... that should work :|

oh. and btw.. the fast idle screw in the tech section isnt on my 120Y a12 carb... i think what it is, is a diapraghm (spelling) and like a shocky that goes onto the accelerator?? is this right???

it's definitely fuel / tune related.
when you press the brake, the booster relies on manifold vaccum to work - your mixtures are probably borderline on stalling and actuating the booster makes it stall completely because it ever-so-slightly changes the inlet mixture.

Adjust your idle and mixture according to manufacturers recommendation check Tech Section Carb ajustment

If you still have the stock carb

Check your carb's fuel-level site glass
when the engine's running the fuel level should be around the centre area of the carb's glass
if its not then you should adjust the float level
check the Tech Section, Carb adjustment article

good luck

ok, well i have been playing around with the idle and mixture screws trying to stop my car from dying at the lights... and i have found that when i push my brakes, my engine starts strugling, and when its cold it will just die if i press the brakes???

this started when i first got the car and i am not sure what is wrong?? please help