Fire problem ... maybe

[MoparFan]

Hi,
so it's a stock '72 318 2bbl :sad2: ... I got it out lastly, start well, idle smoothly, rev well (up to 2500 rpm) when cold... Going for a little ride, to test somethings, about 5 minutes, then the idle was a bite rougher, a little bite of black and blue smoke when revved (2500-3000 rpm). If I raised the rpm from idle slowly to 2000-2500rpm, it sounds like if it misfiring (like if it's not running on all cylinders).
After that, I stopped the car, rested for maybe 20-30 minutes, then started it. Idle well, revved well...

I changed the cap distributor, rotor and plug wire (Accel 8mm), spark plugs have less then an hour of running.

What can cause that misfiring? The coil (most probably the original 34 years old)? The electronic ignition box?

Thanks for your help...

 

[BJR Racing]

With what you have described it sounds like a fuel problem, that when the fuel pump is run at a higher speed than idle that the pump pressure rises to the point that the carb and or the needle and seat can't shut it off and this is where your getting the black and blue smoke from. Too much gas and removing the oil from the cylinder walls creating the blue smoke from oil. I would look at the carb and fuel filters first. The way that I see it is that if the ignition system was failing that it wouldn't change from running well to running poorly, also too much gas will give a misfire as the plugs get fouled. Remove the plugs and see if this isn't your problem. Just some thoughts.

 

[GoodysGotaCuda]

With what you have described it sounds like a fuel problem, that when the fuel pump is run at a higher speed than idle that the pump pressure rises to the point that the carb and or the needle and seat can't shut it off and this is where your getting the black and blue smoke from. Too much gas and removing the oil from the cylinder walls creating the blue smoke from oil. I would look at the carb and fuel filters first. The way that I see it is that if the ignition system was failing that it wouldn't change from running well to running poorly, also too much gas will give a misfire as the plugs get fouled. Remove the plugs and see if this isn't your problem. Just some thoughts.

What he said, and don't forget to just make sure the choke is opening :salut:

 

[MoparFan]

Thanks a lot for the advice on the fuel pressure. I will check that as soon as I can, most probably this weekend. Also, I will try to take a good picture of the plugs, since my analys would not worth that much anyway. :thumblef:

As for the choke, let just say, he is open and hold that way with a steel wire since the mechanism is scrap. :sad2: Thanks for the hint also.

I have so much stuff to learn on the troubleshooting of that thing...well one problem at the time I guess. :drinkers:

Thanks again

 

[MoparFan]

well big thanks BJR Racing, you were 100% rigth. I checked the carb this weekend, and the needle was not working well at all. I removed it, cleaned the needle and put it back together ... then :thumblef: :notworth: :drinkers:

I think even if it's a small 2bbl I will rebuilt it, since it's going on a tired 318, and that the 4bbl I have is much to big for it (750cfm I think). A set of headers and at least I will have a decent running car.

Thanks again

 

[BJR Racing]

Moparfan,
The carb that you stated, the 750 will only run on the front 2 bbls under normal driving conditions, and the secondary's will only start to come on @ about 2800 or higher rpms. Then at this point they are just begining to open. The primaries on a 750 are about equal to the small 2 bbl that the 318 comes with, about 375 cfm's, so it should work fine on the little engine. As long as it's a vac. sec. and not a DP.