The Ford Barn

Barlea · 04-29-2013, 09:41 PM

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Ever wonder what that little spring was doing on the fuel pump linkage? Apparently it allows the hook that pulls the diaphragm to use full stroke when sucking air until the pump primes and carb float bowl fills, then as the float closes the valve, the diaphragm "squats down" on the 2 1/2 lb spring, holding the last stroke of fuel above it against the float valve until it opens slightly as fuel is used. When the pump diaphragm "squats down" on the spring, it takes the slotted pull rod down with it, but because of the little spring on the linkage, the hook is able to follow and maintains contact with the pull rod and is able to stroke the diaphragm ever so slightly when the carb calls for fuel and maintains an equilibrium with the carb float. Thus, although the pump pushrod and linkage is still maintaining full .200 movement, the pump is able to "idle" and hold pressure on the carb.
In Victor Pages book "Ford V8 Cars and Trucks", Ford compares the 4 cylinder fuel pump to the V8 pump.. "The spring on the V8 pump keeps the push rod against the eccentric on the camshaft and pulls the diaphragm downward. The corresponding member on the 4 cylinder pump was merely for the purpose of keeping the pushrod rocker arm in constant contact with the eccentric on the camshaft. ..... In average driving, the movement of the diaphragm is confined to but several thousandths of an inch. Fuel pump pressure should not be not less than 1 1/2 lbs or more than 3 1/2 lbs at any speed. Pump should prime in 20 seconds or less when engine is cranked with starter". ..B.

04-29-2013, 09:41 PM	#1
Barlea Senior Member Join Date: May 2010 Location: West Central Alberta Posts: 441	Fuel Pump Sponsored Links (Register now to hide all advertisements) Ever wonder what that little spring was doing on the fuel pump linkage? Apparently it allows the hook that pulls the diaphragm to use full stroke when sucking air until the pump primes and carb float bowl fills, then as the float closes the valve, the diaphragm "squats down" on the 2 1/2 lb spring, holding the last stroke of fuel above it against the float valve until it opens slightly as fuel is used. When the pump diaphragm "squats down" on the spring, it takes the slotted pull rod down with it, but because of the little spring on the linkage, the hook is able to follow and maintains contact with the pull rod and is able to stroke the diaphragm ever so slightly when the carb calls for fuel and maintains an equilibrium with the carb float. Thus, although the pump pushrod and linkage is still maintaining full .200 movement, the pump is able to "idle" and hold pressure on the carb. In Victor Pages book "Ford V8 Cars and Trucks", Ford compares the 4 cylinder fuel pump to the V8 pump.. "The spring on the V8 pump keeps the push rod against the eccentric on the camshaft and pulls the diaphragm downward. The corresponding member on the 4 cylinder pump was merely for the purpose of keeping the pushrod rocker arm in constant contact with the eccentric on the camshaft. ..... In average driving, the movement of the diaphragm is confined to but several thousandths of an inch. Fuel pump pressure should not be not less than 1 1/2 lbs or more than 3 1/2 lbs at any speed. Pump should prime in 20 seconds or less when engine is cranked with starter". ..B.