See Figures 1 and 2
A single-action, diaphragm-type mechanical fuel pump is found on all carbureted models, with the possible exception of 1980-82 4-140 turbo models equipped with an automatic transmission.
The mechanical fuel pump, which is driven by the camshaft, is located at the lower left side of the cylinder block on the 6-170 engine, at the right front cover on the 6-232 engine, and at the left side of the cylinder block or front cover on 4-140, 6-200 and V8 models.
No adjustments may be made to the fuel pump. Before removing and replacing the old fuel pump, the following test may be made while the pump is still installed on the engine.
- If a fuel pressure gauge is available, connect the gauge to the engine and operate the engine until the pressure stops rising. Stop the engine and take the reading. 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. Also 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 fuel tank and inlet line.
- If a fuel pressure gauge is not available, disconnect the fuel line at the pump outlet, place a vessel beneath the pump outlet, and crank the engine. A good pump will force the fuel out of the outlet in steady spurts. One pint in 25-30 seconds is a good flow. A worn diaphragm spring may not provide proper pumping action.
- 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, no suction indicates that the pump diaphragm is leaking, or that the diaphragm linkage is worn.
- Check the crankcase for gasoline. A ruptured diaphragm may leak fuel into the engine.
REMOVAL & INSTALLATION
Before removing the pump, rotate the engine so that the low point of the cam lobe is against the pump arm. This can be determined by rotating the engine with the fuel pump mounting bolts loosened slightly. When tension (resistance) is removed from the arm, proceed.
- Disconnect and plug the inlet and outlet lines at the fuel pump.
- Remove the fuel pump retaining bolts and carefully pull the pump and old gasket away from the cylinder block or cover.
- Discard the old gasket. Clean the mating surfaces on the block or cover and position a new gasket, using oil-resistant sealer.
- Mount the fuel pump and gasket to the engine block or cover, being careful to insert the pump lever (rocker arm) in the engine block, aligning it correctly above the camshaft lobe.
If resistance is felt while positioning the fuel pump on the block, the camshaft lobe is probably on the high position. To ease installation, connect a remote engine starter switch to the engine and tap the switch until resistance fades.
- While holding the pump securely against the block, install the retaining bolts. On 4 and 6-cylinder engines, torque the bolts to 12-15 ft. lbs.; on V8 engines, torque the bolts to 20-24 ft. lbs.
- Unplug and reconnect the fuel lines at the pump.
- Start the engine and check for fuel leaks. Also check for oil leaks where the fuel pump attaches to the block.