The mechanical fuel pump is located on the engine block or on the cylinder head. Normally, it is a sealed unit that cannot be repaired.
- It should be inspected for fuel leaks.
- If gasoline is leaking at the line fittings, these fittings should be tightened to the specified torque.
- If the fuel leak is still present, replace the fittings and/or fuel line. When gasoline is leaking from the vent opening in the pump housing, the pump diaphragm is leaking and fuel pump replacement is necessary.
- If engine oil is leaking from the vent opening in the pump housing and the PCV system is working properly, the push rod seal is worn and pump replacement is required.
- A loose pivot pin may cause oil leaks between the pin and the pump housing. When oil is leaking between the pump housing and the engine block, the pump mounting bolts should be tightened to the specified torque. If the oil leak continues, the gasket between the pump housing and the engine block must be replaced.
- The pump should be checked for excessive noise. If it makes a clicking noise when the engine is operating at a fast idle, the small spring between the rocker arm and the pump housing is broken or weak.
- If engine performance indicates inadequate fuel, the pump, while mounted on the engine, should be tested for pressure and volume. Incorrect fuel pump pressure and low volume are the two most likely fuel pump troubles that affect engine performance. Low pressure causes a lean mixture. Excessive pressure causes high fuel consumption and an overly rich mixture that can result in fuel injection or carburetor flooding. Low volume causes fuel starvation at high speeds.