I just grabbed a 1979 Datsun 620 for a daily runner my room mate could use. His Kia took a s*** and he just needed some basic transportation until he could find a better car to invest some money into. I grabbed this Datsun because it was only $800, had 90,000 original miles the dash was perfect and everything worked. It started first crank and idled right away every time i started it. it did run a little rough once it got warmed up but it would clear up with a few taps of the gas pedal. I figured that it was just a tuning issue and i could iron it out. Well i drove the truck to my work and it scooted along perfectly the whole way. But as soon as i started it up to go home everything went to hell.

It started perfectly as usual and then suddenly as i took off it died. Nothing. i started it again and tried to rev it up and it would rev for a second and then cut out %100. I soon figured out that the only way to keep it running was to pump the gas constantly. I figured that the mains were plugged if i could run it off of the accelerator pump. So i pumped it into the parking lot of an ORileys and started poking around with no luck. I finally managed to get the air cleaner off, by removing all 400+ hoses that were attached to it. What i was met with though was not a carb, it was something far far more sinister.

Soon some guys coming out of the parts store stopped and gave me a hand. We tested the fuel pump first and it was a little weak, but certainly working. They were convinced that it was the fuel pump not putting out enough pressure. Which seemed weird to me because the truck had run fine earlier that afternoon and a mechanical pump just wouldn't cut out like that. But i went into the auto parts store and bought a universal electric pump and put it inline hoping it would do the trick. No luck same BS. So i took it off, hooked the mechanical pump back up and walked to a gas station to get a drink and to calm down.

When i got back i started playing with the carb again and i figured out a way to keep it idling. I jammed a piece of cardboard between the choke and the air cleaner holding it shut. This let the car idle and rev all the way through the RPM's strongly for about a second before it started dieing and doing the same BS with the accelerator pump. But the good news was that with my little cardboard brace the pump technique was much much more effective and i was able to drive all the way home like that.

so now i sit with a bum truck out front of my house and a cramped leg, wondering to myself what to do. I was planning on ditching all the smog nonsense from this car but i was thinking i would have a little time to find all the parts i needed. I already have a weber 32/36 progressive and an Offenhauser manifold but they are in Cali right now and i would have to get them shipped. And from what i hear it wont work with the stock exhaust which looks like it has a bunch of junk for the air injection on it any way.

So essentially i need one of two things.

1. i need a simple fix, if this is easily answered then by all means i will go trouble shoot it real fast. Anyone got any ideas?

2. a place where i can get the parts to ditch all the Smog BS so i can rush to get it all off. And if someone could tell me exactly what i can ditch that would be amazing.

i'm pretty sure you can ditch everything except for the dizzy vac advance if its anything like the other datsuns i've seen. that means undo and cap all lines except for the one to the dizzy

other than that, your problem sounds to either be fuel or vacuum related. the reason that the pump may have been weak when testing it may be because something clogged the lines to it from the tank being old etc. so possible clogged lines or filter. and as i also said, it sounds like a possible vacuum issue so when you get done deleting everything it might clear up on its own

I would have to say that it could be either dirt got into carb jet or you need a new accelerator pump which is in the carb. With the air cleaner off you should now see the top of the accelerator pump shaft. It's located on top of the carb and offset to the side next to the valve cover. It has a little or should rubber bellow to keep dirt off/out of the seal. That is why you are pumping like mad to keep it running. I had the same problem but it was the pump. You will need the numbers off of the carb. Take those numbers to your local NAPA and they can help you locate a rebuild kit.