Carbureted engines are equipped with mechanical fuel pumps.
No adjustments may be made to the fuel pump. Before removing and overhauling the old fuel pump, the following test may be made to determine if replacement is necessary.
- If a fuel pressure gauge is available, connect the gauge to the engine and crank the engine (with the key or a remote starter switch) until the pressure stops rising and record the highest pressure achieved. If the reading is within the specifications given in the Tune-Up Specifications chart in Engine Electrical , the malfunction is not in the fuel pump. Check the pressure drop after the engine is stopped. A large pressure drop below the minimum specification indicates leaky valves. If the pump proves to be satisfactory, check the tank and inlet line.
- If the fuel pressure gauge is not available, disconnect the fuel line at the pump outlet, place an approved gasoline container beneath the pump outlet, and crank the engine. A good pump will force the fuel out of the outlet in steady spurts. A worn diaphragm spring may not provide proper pumping action. Check the output through several strokes of the pump, looking for any sign of reduced flow or air bubbles.
- As a further test, disconnect and plug the fuel line from the tank at the pump, and hold your thumb over the pump inlet. If the pump is functioning properly, a suction should be felt on your thumb when the engine is cranked. No suction indicates that the pump diaphragm is leaking or that the diaphragm linkage is worn.
- Check the crankcase for gasoline. One quick check is to pull the dipstick and smell the oil; a better check is to examine a large sample (such a pan of recently drained oil) for odor and/or pollution. Gasoline will thin the oil in a fashion very similar to the effect of paint thinner in paint. A ruptured diaphragm can allow fuel to enter the oil system. This condition must be remedied as soon as possible. Damage to engine bearings can result if the oil is polluted with fuel.
REMOVAL & INSTALLATION
See Figure 1
- Label, disconnect and plug the inlet and outlet lines to the fuel pump.
- Remove the two fuel pump retaining bolts, then carefully pull the pump and old gasket away from the block.
- Discard the old gasket and position a new one on the pump to be reinstalled.
- Mount the fuel pump and gasket to the engine block. Be careful to insert the pump lever (rocker arm) into the engine block and align it correctly above the camshaft.
- While holding the pump securely against the block, install the two fuel pump retaining bolts, and tighten them securely.
- Unplug and reconnect the fuel lines to the pump. Make sure the correct line is connected to each port.
- Start the engine and check for fuel leaks. Also check for oil leaks where the pump attaches to the block. Depending on how much fuel was lost with the hoses disconnected, the engine may crank longer than normal before starting.