The fuel pump is the single action AC diaphragm type. All vehicles covered by this guide were originally equipped with a non-serviceable fuel pump. Should a non-serviceable pump fail, it must be replaced as an assembly.
The pump is actuated by an eccentric located on the engine camshaft. On inline engines, the Buick produced 231 V6 engine and the Oldsmobile produced 307 V8 engine, the eccentric actuates the pump rocker arm directly. On other V8 and 200 V6 engines, a pushrod between the camshaft eccentric and the fuel pump actuates the pump rocker arm.
TESTING THE FUEL PUMP
The 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 noticed from 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, then disengage the HEI system 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 using 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 located in of this guide. 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/low, the pump should be replaced.
- Remove the pressure gauge, then reconnect and secure all fuel lines.
REMOVAL & INSTALLATION
When you are disconnecting or connecting the fuel pump outlet fitting, always use 2 wrenches to avoid damaging the pump.
- Raise the hood and determine if the pump is accessible from above. If access is not available from above, raise the front of the vehicle and support safely using jackstands.
- Disconnect the fuel intake and outle lines at the pump. Be sure to plug the pump intake line in order to prevent system contamination or excessive fuel loss.
- On Chevrolet produced V6 and V8 engines, remove the upper bolt from the right front mounting boss. Insert a longer bolt ( 3 / 8 -16 × 2") in this hole to hold the fuel pump pushrod up and out of the way.
- Remove the two pump mounting bolts and lockwashers; then remove the pump and its gasket from the engine.
- If the rocker arm pushrod is to be removed from Chevrolet V6 or V8 engines, remove the two adapter bolts and lockwashers, then remove the adapter and its gasket for access to the pushrod.
- Thoroughly clean the gasket mating surfaces of all old material or sealer.
- If removed, install the pushrod, then install the adapter using a new gasket and secure using the retaining bolts.
- Coat the mating surfaces with a suitable sealer, then install the fuel pump assembly using a new gasket.
On vehicles equipped with a pushrod to actuate the fuel pump rocker arm, if a bolt was not used to secure the pushrod it may interfere with pump installation. A small screwdriver or thin plastic tool may be used to hold the pushrod up and out of the way while the fuel pump is installed. Make sure the pump rocker arm is properly located under the pushrod. Another method of retaining the pushrod it to pack it into position using grease, though this will only work on a cold engine.
- Install the fuel pump to the engine using a new gasket
- Install and tighten the pump retaining bolts.
- If applicable, remove the bolt retaining the pushrod out of the way and reinstall the original bolt to the mounting boss.
- Remove the plug, then connect the fuel tank line to the pump.
- Using a backup wrench to protect the pump housing, install and tighten the outlet line to the pump.
- If the vehicle was raised, remove the jackstands and carefully lower car.
- Start and run the engine, then check for leaks.