See Figure 1
The fuel pump is bolted to the lower left side of the cylinder block. It is mechanically operated by an eccentric on the camshaft which drives a pushrod. The fuel pump cannot be disassembled for repairs and must be replaced if testing indicates it is not within performance specifications.
REMOVAL & INSTALLATION
See Figure 2
- Disconnect the negative battery cable.
- Remove the fuel tank filler cap, to allow any pressure in the tank to escape.
- Place a drip pan below the fuel pump to catch any spilled fuel.
- Tag or mark the fuel lines to the pump.
- Loosen the fuel line nut at the pump inlet and outlet, using a flare-end wrench or suitable open-ended wrench. Fuel will spill out of the connection when loosened.
- Loosen the fuel pump mounting bolts approximately two turns. Apply force with your hand to loosen the fuel pump if the gasket is stuck. If excessive tension is on the pump, rotate the engine crankshaft pulley retainer bolt until the fuel pump cam lobe is near its low position.
- Disconnect the fuel pump inlet and outlet lines using a suitable flare or opened-ended wrench.
- Remove the fuel pump attaching bolts and remove the pump and gasket. Discard the old gasket.
- Remove all gasket material from the engine and fuel pump mating surfaces.
- Position the attaching bolts into the fuel pump and install a new gasket on the bolts. Position the fuel pump to the pushrod and the mounting pad on the engine. Turn the attaching bolts alternately and evenly. Tighten them to 14-21 ft. lbs. (19-29 Nm).
- Connect and tighten the fuel outlet and inlet lines.
- Connect the negative battery cable, and install fuel tank cap.
- Start the engine and check all connections for fuel leaks. Stop the engine and check all fuel pump fuel line connections for fuel leaks by running a finger under the connections. Check for oil leaks at the fuel pump mounting pad.
If a problem exists with the fuel pump, it normally will deliver either no fuel at all, or not enough to sustain high engine speeds or loads. When an engine has a lean (fuel starvation) condition, the fuel pump is often suspected as being the source of the problem, however similar symptoms will be present if the fuel filter is clogged or the fuel tank is plugged or restricted. It could also be a carburetor problem, kinked or plugged fuel line or a leaking fuel hose.
Before removing a suspect fuel pump:
- Make sure there is fuel in the tank.
- Replace the fuel filter to eliminate that possibility.
- Check all rubber hoses from the fuel pump to the fuel tank for kinks or cracks.
- With the engine idling, inspect all fuel hoses and lines for leaks in the lines or connections. Tighten loose connections.
- Check the fuel pump outlet connection for leaks and tighten if required.
- Inspect the fuel pump diaphragm crimp (the area where the stamped steel section is attached to the casting) and the breather hole(s) in the casting for evidence of fuel or oil leakage. Replace the fuel pump if leaking.
See Figure 3
- Remove the gas tank cap.
- Remove the carburetor air cleaner.
- Slowly disconnect the fuel line at the fuel filter. Use clean rags to catch any fuel spray. Exercise caution as the fuel line is pressurized and take precautions to avoid the risk of fire.
- Place a suitable non-breakable container (1 pint minimum capacity) at the end of the disconnected fuel line. A small piece of hose may be necessary on the fuel line end.
- With the high tension wire removed from the coil, crank the engine ten revolutions to fill the fuel lines, then crank the engine again for 10 seconds and measure the fuel collected. The pump should deliver roughly 1 / 3 pint (0.16 liters) of fuel, minimum.
- If the fuel flow is within specifications, perform a pressure test.
- If the fuel flow is low, repeat the test using a remote vented can of gasoline. Remove the fuel pump inlet hose, then connect a length of fuel hose to the pump inlet and insert the other end into the remote gasoline can. If the fuel flow is now within specifications, the problem is a plugged in-tank filter or a leaking, kinked or plugged fuel line or hose. Make sure the fuel pump pushrod length is 6.10-6.14 in. (155-156mm); if short, replace the pushrod and install the fuel pump. If the fuel flow is still low, replace the fuel pump.
- Connect a 0-15 psi fuel pump pressure tester (Rotunda No. 059-00008 or equivalent) to the carburetor end of the fuel line.
- Start the engine. It should be able to run for about 30 seconds on the fuel in the carburetor. Read the pressure on the gauge after about 10 seconds. It should be 4-6.5 psi (31-45 kPa).
- If the pump pressure is too low or high, replace the fuel pump and retest.
- Once all testing is complete, reconnect the fuel lines and remove the gauge.