i had a problem with my 67 ford mustang coupe. it has a 6 cylinder engine and an auto tranny. i only use it occasionally. recently it would not start. the mechanic cleaned the carb, replaces the spark plugs, condenser and contact point. and checkeked on the timing. we also installed a new fuel pump. we also cleaned the gas tank and replaces both the fuel pump and filter with a new one. it start but after running it for a few miles, the engine suddenly splutter. black smoke spewd from the exhaust. it would still start but only if i step on the aceelarator. engine will stop once a get mu foot off the accelarator. i really have to step on the accelerator just to keeo the engine running. where do you think is the problem. my carb is a rebuilt one. should i buy a new one??? please help, i 've spent a lot already and i havent still solved the problem

 

Mario,
Black smoke equals too much fuel. The reason the engine will run under full throttle is that you are allowing more air to mix with the excess fuel. When you let off the throttle there is not enogh air to keep the engine running and it dies from the excess fuel. Your problem is most likely in the carb. First, make sure the choke is fully opened once the engine warms up. If it does not open completely, make sure the choke is properly adjusted and the linkage is moving freely. If the choke is OK, your problem is either a sticking float, or a small hole in the float which allows fuel to fill the float itself and prevents the float from rising and closing the float needle. One other possibility is a bad needle or seat. Hope this helps.

John

 

i had the same problem with my 67. i have a 302 but my problem was the carb. i had dirt stuck in the needle which put constant fuel into the motor without air. Hope this helps

 

Mario, good luck getting it sorted. I am moving this to the classic forum, but will leave a link here