fuel pump is a mechanical pump, bolted to the timing chain cover.
arm rides the eccentric bolted to the front of the camshaft. As the
camshaft spins, the arm pivots on its fulcrum. This motion pulls and
pushes a diaphragm. As it pulls, it draws fuel from the fuel tank,
via fuel lines into the inlet. An inlet check valve prevents fuel
from returning when the diaphragm is pushed. Internal springs push
the diaphragm back. When the diaphragm pushes the fuel past the outlet
check valve, it is then pressurized in the line to the carburetor.
The check valve prevents fuel form returning into the fuel pump. Another diaphragm
is inside the pump fuel cavity. It creates an air pocket to minimize the pulsating
of the fuel as it passes through the pump.