The 1963-81 Corvette fuel pump is a mechanically operated diaphragm-type pump. The camshaft of the engine has an eccentric (similar to a cam lobe, but more rounded) cast as part of the camshaft. As the camshaft rotates, the eccentric actuates a pushrod which pushes the fuel pump rocker arm to activate the pump.
The fuel pump is attached to the right front of the cylinder block. On small-block engines, a fuel pump mounting plate is used, with two gaskets; one between the pump and the plate; the other between the plate and the block. Pumps on big-block engines attach directly to the block and use only one gasket.
The inlet, or suction line of the pump, draws fuel from the tank. The outlet, or pressure line of the pump, supplies pressurized fuel to the carburetor (or fuel injection unit, in early Corvettes). Some models use a third line, which is a vapor return. The purpose of the vapor return is to route the hot fuel and fuel vapor from the pump back to the fuel tank, which considerably reduces the chance of vapor lock.
For all intents and purposes, the fuel pump is not rebuildable. Some 60s Corvettes used a rebuildable pump, though parts for these pumps are no longer available from Chevrolet.
If the engine exhibits a tendency to "starve-out", never assume that the fuel pump is defective until you test the pump. In most cases, a "starve-out" condition is caused by a weak ignition system, plugged fuel filter, or restricted fuel line.
- Disconnect the fuel line from the carburetor. While this line is disconnected, check the fuel filter.
- Run a piece of fuel-resistant rubber hose from the line to a graduated container.
- On engines with standard ignition systems, ground the secondary coil wire. On engines with the HEI distributor, disconnect the BAT connector from the coil terminal.
- Crank the engine. Fuel should be pumped into the container at a rate of 1 pint in 30 seconds.
- Remove the added hose and container and connect a fuel pressure gauge to the fuel line. Crank the engine and read the highest pressure obtained on the gauge. See the Tune-Up Specifications chart in Engine Performance And Tune-up for the proper fuel pump pressure range.
If the pump failed the tests of either Step 4 or 5, replace the pump as previously outlined. If the pump checked okay, remove the pressure gauge and reconnect the fuel line to the carburetor. Reconnect the ignition wiring as originally connected.
REMOVAL & INSTALLATION
See Figure 1
- Disconnect the fuel inlet, outlet, and vapor return (if equipped) lines from the pump.
- On small-block engines, remove the bolt from the front right face of the engine block which is almost opposite the forward pump mounting bolt. Insert a longer bolt ( 3 / 8 X 16 X 2 in.) in this hole and snug down the bolt. This will hold the fuel pump pushrod in place. On big-block engines, the pushrod can be retained with heavy grease or mechanical fingers during installation.
- Remove the fuel pump mounting bolts and remove the fuel pump.
- Installation of the pump is the reverse of the previous steps. Replace the fuel pump gasket(s) during installation. Start the engine and check the pump for proper operation, and check for leaks.