Re: 64 9.5 fuel delivery questions
You can eliminate the fuel pump as the cause of your problem in one of two ways: elevate the fuel tank above the engine so that gravity fills the float bowl; or keep a little steady pressure on the primer bulb. If either method fails to keep the engine running without the choke, the fuel pump is not the problem.
Since all the fuel pump does is lift fuel to the float bowl to keep it filled, it is unlikely that it is responsible for your problem.
The engine pulls the air and fuel through the carburetor. When you can keep the engine running only with the choke on, the engine is running lean and needs more gas in the fuel/air mix. The choke prevents air from entering the carburetor, thus forcing the engine to pull a richer fuel/air mixture. You want to enrich the mix for cold starting, but not after that.
At idle, the fuel/air mix is controlled by the lean/rich needle; turning the needle counter-clockwise adds more fuel to the fuel/air mix. The needle must seat properly, have the correct seals and be properly adjusted while running under load in order for the engine to perform optimally.
Additionally, the high speed jet, which lies horizontally behind the drain plug on the float bowl, must be kept open and clear of any debris. Aerosol carburetor cleaner blown into the jet should emerge from a small hole at the base of the throttle plate if the orifice is clear.
The 1964 and 1965 9.5 carburetors had a different needle valve setup than the later models, and did not use a spring. I'll see if I can find a diagram and add it to this thread.
