A positive displacement gear-type fuel pump is attached to the governor or
blower on the In-line engines and to the flywheel housing on the V-type
A spring-loaded relief valve, incorporated in the pump body, normally
remains in the closed position, operating only when the pressure on the
outlet side (to the fuel filter) becomes excessive due to a plugged filter or
The fuel pump incorporates two oil seals. Two tapped holes are provided in
the underside of the pump body, between the oil seals, to permit a drain
tube to be attached. If fuel leakage exceeds one drop per minute, the seals
must be replaced. An authorized Detroit Diesel Allison Service Outlet is
properly equipped to replace the seals.
Fuel pumps are furnished in either left or right-hand rotation, according to
the engine model, and are stamped RH or LH. These pumps are not
interchangeable and cannot be rebuilt to operate in an opposite rotation.
Fuel Strainer and Fuel Filter
A replaceable-element type fuel strainer and fuel filter (Fig. 4) are used in
the fuel system to remove impurities from the fuel. The strainer removes
the Mounting larger particles and the filter removes the small foreign
Fig. 4. Typical Fuel Strainer and Filter Mounting
The fuel strainer and fuel filter are basically identical in construction, both
consisting of a cover, shell and replaceable element. Since the fuel strainer is placed between the fuel supply tank and the fuel pump, it
functions under suction; the fuel filter, which is installed between the fuel pump and the fuel inlet manifold in the cylinder head, operates
Replace the elements as follows:
1. With the engine shut down, place a suitable container under the fuel strainer or filter and open the drain cock. The fuel will drain
more freely if the cover nut is loosened slightly.
Support the shell, unscrew the cover nut and remove the shell and element.
3. Remove and discard the element and gasket. Clean the shell with fuel oil and dry it with a cloth or
4. Place a new element, which has been thoroughly soaked in clean fuel oil, over the stud and push it down on the seat. Close the
drain cock and fill the shell approximately two-thirds full with clean fuel oil.
Affix a new shell gasket, place the shell and element into position under the cover and start the cover nut on the shell stud.
Tighten the cover nut only enough to prevent fuel leakage.
7. Remove the plug in the strainer or filter cover and fill the shell with fuel. Fuel system primer J 5956 may be used to prime the fuel
Start and operate the engine and check the fuel system for leaks.
Spin-On Type Fuel Filter
A spin-on fuel strainer and fuel filter (Fig. 5) is used on certain engines. The spin-on filter cartridge consists of a shell, element and
gasket combined into a unitized replacement assembly. No separate springs or seats are required to support the filters.