Motorcraft 2100 Accelerator Pump

Motorcraft 2100 2 Barrel Carburetor Check Weight
Check Weight

This check weight is used in the main discharge. 1st the check ball, then the check weight. The check weight is used to hold down the check ball when the engine is not accelerating. Without it, the check ball would float up and allow fuel to be siphoned out.

When accelerating, the fuel pressure will lift the check ball and check weight to all fuel to flow into the venturi.

Measurements don’t have to be exact. What is important to watch is that the weight has enough room to move up slightly when fuel is being forced into the discharge.

Motorcraft 2100 Pre 1964 Accelerator Pump
Pre 1964 2100. The 1964 and later is different.

A- Fuel enters here from the float bowl.
B- Check ball drops down this hole to block off the fuel. The suction from the pump returning and the weight of the fuel raises this check ball and allows fuel to enter the accelerator pump cavity.
C- This screw is used to stop the check ball from floating out of the hole.

Motorcraft 2100 2 Barrel Carburetor Parts
1964 and later was different. The center of the housing used a hole with a rubber check valve instead of the A & B scenario.

A – Relief hole – This hole has two jobs. One is to relieve air pressure when the pump diaphragm is moving back and forth. Two is to alert you that the diaphragm has ruptured. Any fuel out of this hole indicates a bad diaphragm.

Is the pump cover leaking around the gasket? If so, then it is warped. You can put it in a vise and using flat stock to sandwich it apply heat, then tighten the vise slightly and let it cool. 
You can also use a flat file and run across the 4 corners. They are probably too high. Doesn’t take much.

Updated on 12/17/2020

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