Carter AFB (300hp) issues

[Gerald C.]

I was at a show today and when I went to leave my, 63 didn't start. (it's been starting wonderfully every time I go out). After fiddling with it with some help from my friends it was determined that the carb was not getting fuel. One of the fellas said that the accelerator pump is probably not squirting fuel and after he opened the throttle fully (more than I had my accelerator rod set) the car fired right up.

My question is: should I extend the accelerator rod a bit so that the Accelerator pump opens fully (more than it is now)?

Thoughts?

Thanks

[Kent S.]

Re: Carter AFB (300hp) issues

The accelerator pump squirts immediately from the idle position so I'm not following what went on in your post.

[Gerald C.]

Re: Carter AFB (300hp) issues

Kent,

I don't know how else to explain it other than what the person helping me saw (or didn't see) in the carburetor as I was in the car trying to get it started.

[Duke W.]

Re: Carter AFB (300hp) issues

If the car would not start until the throttle was fully opened up, it could have just been a case of flooding due to fuel percolation. In this case the fuel level in the bowls could be so low that there is no accelerator pump discharge until well into its travel, and with a flooded engine the last thing you want is more fuel. Percolation issues can occur up to an hour or even two after engine shutdown in hot summer weather.

Your owner's manual has instructions on how to start a flooded engine. Basically you hold the throttle wide open and crank the engine until it starts. A lot of guys don't understand this because they either forgot or don't have recent experience with carbureted engines in hot summer weather.

There are air-fuel ratio ignitability limits, both on the lean and rich side of the spectrum. With the throttle held wide open there is not enough vacuum at the venturi nozzles or manifold to draw fuel in. Thus, the engine is just pumping air and after a few seconds of cranking the excess fuel should be purged and the engine should fire. If the engine does not start after a 5-6 seconds of cranking, stop cranking but keep the throttle to the floor. Wait a few seconds and crank again, and repeat this process until the engine starts.

Severe flooding that wets down the spark plugs may not start, but this is more likely to happen on a cold start... happened to me once on my Honda CB1100F, and I had to swap out the plugs to make the ride.

One data point does not mean a trend (unless you're a democrat pollster or left wing economist trying to bully the Fed into lowering the federal funds rate). so maybe wait and see what happens the next few times you drive it, and if it reoccurs, use the flooded engine start procedure.

It's a good idea to wire the heat riser valve open as this should cool down the fuel bowls. It might cause some minor cold engine start-off issues, but they should clear up within a few minutes as the engine warms.

Your 1963 Corvette Shop Manual has an excellent section on the AFB... so you might consider going over all the adjustments to make sure everything is in spec.

The next time you shut down the fully warmed up engine, remove the air cleaner lid and check for fuel dripping out of the venturi nozzles. If so, a float level is too high or a needle and seat is leaking.

Duke

[Gerald C.]

Re: Carter AFB (300hp) issues

Thanks Duke,

I'll work on your information later today.

Much appreciated!

Jerry

[Robert B.]

Re: Carter AFB (300hp) issues

great info. Thanks

[Gerald C.]

Re: Carter AFB (300hp) issues

I adjusted the accelerator rod... shortened it a bit and it seems that the car started quicker. But it's not hot out just yet. I'll try again when the car cools down. I measured the height of the accelerator pump "valve" as it stood exposed from the carb body and it measured exactly 1/2" as the repair manual indicates.