Fuel Feeder Fix
Rebuilding an early fuel regulator
Earl Duty - April 19, 2012 10:00 AM
1 After removing the brass fittings, disassembly starts by extracting eight retaining screws holding the cover to the canister.
2 With the eight retaining screws removed, our cover and float assembly was carefully lifted free from its tomb.
3 The “lower chamber” lifts out of the canister and is shown here with its “flapper valve” attached.
4 Testing the float consists of submerging the unit into a container of hot tap water. If the float is defective, bubbles will appear. No bubbles here, so our float passed the test.
5 We carefully blasted the upper cover using glass beads, and then gave it a thorough cleaning in a solution called Purple Power. This cleaning product is available at most well-stocked parts stores. Caution: this product is corrosive. Follow directions on the can, wear gloves, and use safety glasses.
6 The brass check valves can be cleaned using any spray carburetor and choke cleaner.
7 This diagram shows the unit and its components. At first glance it may seem like this device is a complicated piece of engineering.
8 Our Stewart vacuum fuel supply unit is identical to the one mounted on the firewall of this 1928 Chevy truck. This also shows how our fuel supply unit is plumbed into the intake, carburetor, and fuel tank.
9 The components are now cleaned, painted, and ready for reassembly in reverse of disassembly.
10 After assembly, our unit is once again fit for duty!
Our restoration/repair of a vacuum fuel supply canister focuses on the typical Stewart unit used on the 1916-’28 Chevrolets. similar Stewart units were used on many other makes and models during the teens, ’20s and ’30s.
The unit is comprised of a small tank attached to the firewall under the hood, mounted away from and above the level of the carburetor. The purpose for mounting it above the carburetor is for gravity feed. The unit is connected to the fuel tank, the intake manifold, and the carburetor via a series of brass fittings and copper lines. When the engine is cranking or running, a vacuum is created within the canister, which draws fuel from the fuel tank.
The incoming fuel then fills the upper chamber until the float reaches a pre-set level. When the float reaches the end of its travel, a valve located in the top cover closes, shutting off the vacuum (suction) supplied by the engine. This action in turn releases the fuel via the “flapper valve” into the lower part of the canister. As the fuel enters the lower section of the canister, the float drops, unseating the valve, which again allows engine vacuum to restart the siphoning of fuel from the fuel tank. To simplify: it’s a continuous, suction, fill, and release procedure, assuring an ample supply of fuel to the carburetor under all driving conditions.
Troubleshooting a Stewart Vacuum Fuel Supply
If no fuel exits the carburetor supply valve when opened, check for lack of fuel in the fuel tank or for loose or bad fuel line connections, allowing the unit to suck air instead of fuel. Also check for loose or bad connections at the intake manifold, robbing the fuel supply unit of necessary vacuum needed for proper operation. If the vent tube overflows on a regular basis, check the fuel cap for being plugged or the vent hole being too small.
If there is fuel in the tank and all connections to the unit are sealed, then follow the story showing disassembly, inspection, cleaning and repairs of the fuel supply unit. After a repair/rebuild, it’s a good idea to prime the supply tank with one pint of fresh gasoline. This is accomplished by removing the brass fitting where it’s marked “fuel line,” and carefully pouring the gasoline in the unit with a small funnel.
Our disassembly started with removing the eight screws attaching the cover to the canister. After carefully inserting a small screwdriver between the cover and the canister, we gently separated the two components. From that point, we extracted the lower chamber from the canister. After testing the float, cleaning the valves in the cover, and thoroughly cleaning and painting the three basic components, we were ready for reassembly.
On some of the components that were pitted and encrusted by years of decay, a bead blast cabinet was used to carefully restore the parts to a like new finish. As it turned out, our Stewart unit simply needed a good cleaning and one new cover gasket.
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