The fuel pump is the single action AC diaphragm type. It is a non-serviceable type fuel pump. The pump is actuated by an eccentric located on the engine camshaft. On inline 6-cylinder engines the eccentric actuates the pump rocker arm. On V8 engines a pushrod between the camshaft eccentric and the fuel pump actuates the pump rocker arm.
Fuel pump should always be tested on the vehicle. The larger line between the pump and tank is the suction side of the system and the smaller line, between the pump and carburetor is the pressure side. A leak in the pressure side would be apparent because of dripping fuel. A leak in the suction side is often only apparent because of the reduced volume of fuel delivered to the pressure side. However, fuel may leak out on the suction side when the engine is off.
- Tighten any loose line connections and look for any kinks or restrictions. Inspect rubber hoses for cracks or leaks and replace if necessary. Inspect the fuel filter for clogging and clean or replace it as necessary.
- Disconnect the fuel line at the carburetor. Disconnect the distributor-to-coil primary wire or, on HEI systems, the distributor connector. Place a container at the end of the fuel line and crank the engine a few revolutions. If little or no gasoline flows from the line, either the fuel pump is inoperative or the line is plugged. Blow through the lines with compressed air and try the test again. Reconnect the line.
- Attach a pressure gauge to the pressure side of the fuel line with a Tee fitting.
- Run the engine and note the reading on the gauge. Stop the engine and compare the reading with the specifications listed in the Tune-Up Specifications chart. If the pump is operating properly, the pressure will be as specified and will be constant at idle speed. If pressure varies sporadically or is too high or low, the pump should be replaced.
- Remove the pressure gauge.