FUEL STRAINER AND FILTER
FUEL STRAINER AND FUEL FILTER
A fuel strainer (primary) and fuel filter (secondary), Fig. 1, are used to remove impurities from the fuel. The
fuel strainer is located between the fuel tank and the fuel pump. The replaceable density-type element is
capable of filtering out particles of 30 microns (a micron is approximately 0.00004 inch). The fuel filter is
installed between the fuel pump and the fuel inlet manifold. The replaceable paper-type element (Fig. 2) can
remove particles as small as 10 microns.
A fuel tank of galvanized steel should never be used for fuel storage, as the fuel oil reacts chemically
with the zinc coating to form powdery flakes which quickly clog the fuel filter and cause damage to the
fuel pump and the fuel injectors.
The fuel strainer and fuel filter are essentially the same in construction and operation, and they will be treated
as one in this section.
The filter and strainer, illustrated in Fig. 3 and 4, consist basically of a shell, a cover, and a replaceable filtering
element. The assembly is made oil-tight by a shell gasket, a cover bolt, and a cover bolt gasket.
The central stud is a permanent part of the shell and, when the unit is assembled, extends up through the cover
where the cover bolt holds the assembly together.
A filter element sets over the central stud inside the shell and is centered in the shell by the stud.
Figure 1. Typical Fuel Strainer and Fuel Filter Mounting
The former and current cover assemblies are visibly different by a cast letter P (primary) that has been added
to the top of the strainer cover and the letter S (secondary) that has been added to the top of the filter cover.
Since the fuel strainer is between the fuel supply tank and the fuel pump, it functions under suction. The filter,
placed between the fuel pump and the fuel inlet manifold in the cylinder head, operates under pressure. Fuel
enters through the inlet passage in the