Below you will find questions customers ask about carburetor problems with our possible solutions. Please keep in mind that we don't have the carburetor, or vehicle at our disposal, so we may have to make some assumptions.
I purchased a 4G float from you. It worked well. Thanks. The carb seems to have a "dead spot" I was hoping you might have some suggestions. The car runs and starts right up. If you accelerate slowly, the car is fine. If you punch it, the car will sometimes die or it will almost die then rush back to life. If you are at a stop and punch it, the car dies but if you accelerate gradually it is fine. You can even floor it after you are moving some and it seems okay. My brother says it might be the accelerator pump. The carb is newly rebuilt and is very clean. Once we got the float fixed it seemed fine. I ran it for a couple of days and this "dead spot" showed up. The carb seems to be adjusted properly and the timing is correct for the engine. Can you help?

I will assume your electrical system is ok. Don't forget that the distributor advance not working correctly can cause a similar problem.

Your friend is probably correct. When you step on the gas an extra squirt of gas is needed and that is provided by the accelerator pump circuit. There is where I would concentrate your efforts. Make sure that the check ball is in the bottom of the pump well, if your carburetor needs one. The way to tell is to look for two holes. One will be slightly up the side near the bottom and that is the discharge hole. The other will be on the bottom and that would be the intake. The check ball that resides here will be the smaller check ball and it is often aluminum.

Test the check ball by taking the top off. Fill the float bowl. The check ball will lift up by the weight of the gas and allow fuel to flow into the well. For those that don't use a check ball, the well if filled by coming over the slot in the side of the pump well. In other words it splashes over from the float bowl. If the well doesn't fill up, then the passage is probably plugged up. Run thin wire through the passage. Ethanol will leave residue behind that cleaners cannot get out.

Take the venturi off, remove the main discharge T, spring and check ball (bigger check ball). Fill the pump well, then press the accelerator pump down to the bottom. The pump well check ball should seal the intake hole and fuel will be forced out to the main discharge. If fuel comes out of the main discharge, then the check ball and passage way is probably ok.

Replace the main discharge check ball and using a brass drift punch, hold the check ball down so that the hole seals. You should now get some resistance when pushing the accelerator pump down. If you get fuel out of the main discharge while holding down the check ball, then use a brass drift punch to gently tap on the check ball. This will reform the check ball hole. Don't hit too hard, or the check ball might get stuck.

Replace the main discharge ball, spring and T. Run thin wire through all of the passages in the venturi cluster and then replace it. Don't forget the gasket.

Now when you press the accelerator pump to the bottom fuel should squirt out of the venturi cluster holes.

Using Startron will help eliminate your ethanol problems.

Tip for cleaning out passages.

Wire from twist ties work well for the small holes. Cleaners and compressed air will not remove the ethanol deposits left behind.
Installing Jets

A piece of paper towel folded over the screwdriver blade will hold the part, or a screw, until it gets started in the hole. (sometimes it helps to dampen the paper towel a bit)

I soaked and cleaned my 2 carb both the 1 inch for a chev . One of them starts and idles good but when you try to raise the rpms it swings frm 1000 to 3000 rpms. It accelerates good if you push the pedal down but if you try to hold the rpms at like 3000 it swings up and down. Ive set the pump and metering rods per yourspecs and cant make it any better.

 

My first instinct is that he has a vacuum leak . . . which could be downstream of the carburetors.
 
Also, are the secondary throttles opening and closing completely? Or is there some sort of interference, including from an incorrect base gasket?

 

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