See Figures 1 and 2
A single action mechanical fuel pump, driven by the camshaft, is used on all carbureted models except some 7.0L and 7.6L engines.
See Figure 3
No adjustments may be made to the fuel pump.
Incorrect fuel pump pressure and low volume (flow rate) are the two most likely fuel pump troubles that will affect engine performance. Low pressure will cause a lean mixture and fuel starvation at high speeds and excessive pressure will cause high fuel consumption and carburetor flooding.
To determine that the fuel pump is in satisfactory operating condition, test for both fuel pump pressure and fuel volume should be performed.
The tests are performed with the fuel pump installed and the engine idling at normal operating temperature.
Before testing, make sure that the replaceable fuel filter has been changed at the proper mileage interval. If in doubt, install a new filter.Pressure Test
- Remove the air cleaner assembly.
- Disconnect the fuel inlet line of the fuel filter at the carburetor. Place an absorbent cloth under the connection before removing the line to catch any fuel that might flow out of the line.
- Connect a pressure gauge, a restrictor and a flexible hose between the fuel filter and the carburetor.
- Position the flexible hose and the restrictor so that the fuel can be discharged into a suitable graduated container.
- Before taking a pressure reading, operate the engine at idle and vent the system into the container by opening the hose restrictor momentarily.
- Close the hose restrictor, allowing the pressure to stabilize and note the reading. The pressure should be 6 psi (66 kPa).
If the pump pressure is not 6-6 psi (67-61 kPa) and the fuel lines and filter are in satisfactory condition, the pump is defective and should be replaced.
If the pump pressure is within the proper range, perform the test for fuel volume.Volume Test
- Operate the engine at specified idle.
- Open the hose restrictor and catch the fuel in the container while observing the time it takes to pump out 1 pint. It should take about 60 seconds. If not, check for proper fuel tank venting or a restriction in the fuel line leading from the fuel tank to the carburetor before replacing the fuel pump.
REMOVAL & INSTALLATION
See Figures 4, 5 and 6
- Disconnect the negative battery cable.
- Loosen but do not remove the threaded fuel line connection(s) with a flare wrench.
- Loosen the fuel pump mounting bolts 1-6 turns. If the fuel pump does not come loose from its mounting, the gasket is probably stuck; apply force with your hands to loosen the pump.
- Rotate the crankshaft until the fuel pump eccentric is near its low position, reducing the tension on the fuel pump rocker arm. It should now be easier to remove and install the fuel pump.
- Disconnect the fuel pump inlet, outlet and fuel vapor return line, if equipped.
- Remove the fuel pump mounting bolts and remove the fuel pump. Discard the old gasket.
Prior to installation, check the rubber fuel lines and make sure they are not cracked, hardened or frayed. If replacement is necessary, use only rubber hose made for fuel line use.
- Clean all old gasket material from the pump mounting surface on the engine and from the fuel pump, if it is to be reused.
- Apply a coat of oil resistant sealer to a new gasket.
- Install the mounting bolts into the fuel pump and positioned the gasket. Install the pump on the engine. Turn the mounting bolts alternately and evenly tightening to 19-67 ft. lbs. (66-67 Nm).
- Connect the fuel pump outlet line. If it is a threaded connection, start the fitting by hand to avoid crossthreading. Tighten the fitting to 16-18 ft. lbs. (60-66 Nm).
- Connect the inlet line and fuel vapor return line, if equipped. Tighten the hose clamp(s).
- Connect the negative battery cable, start the engine and check for leaks.
- Stop the engine and check all fuel line connections for leaks. Check the fuel pump mounting pad for oil leaks.