Figure 1.8. Fuel Metering.
starting will result. The plunger in the fuel pump and the helix opposite the spill port are usually worn
first when dirt is in the fuel.
Most diesel engines use two kinds of fuel filters: a primary or coarse filter between the
supply tank and the fuel supply pump, and a main or fine filter between the supply pump and the
injection pumps. They are made of either metal or fabric. Metal filters are used as primary filters
because the fine particles that pass through them are not as harmful to the supply pump as they would be
to the injection pump. They are cleaned by scraping the metal disks. Because of their greater filtering
qualities, fabric filters are usually used as main filters to protect the fuel injection pump. They have bags
which are turned inside out to get rid of dirt, then washed and reinstalled.
WATER COOLING SYSTEM
Heat originating in the engine is absorbed by circulating water and dissipated in a fan-cooled
radiator. In a diesel-electric locomotive, the fan is driven by a motor powered by an auxiliary generator.
Since heated water helps the engine to reach its best operating temperature more quickly, the radiator is
not brought into the water circuit until the water is quite hot. Temperature of the water can be regulated
by louvers on the front of the radiator.
The water is circulated by a pump driven from the engine. It goes through water jackets between
the cylinders and cylinder liners, and is then routed through the radiator to be cooled. With a well-
regulated radiator, water enters the engine at 100-120 F. and leaves it at 150-180 F. Because heat
and cold cause metal to expand and contract, it is better to use a high rate of water circulation with a
small difference in temperature of the water entering and