Quantcast Electronic Fuel Injection

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TM 5-685/NAVFAC MO-912
Table 3-l. Unit injector system.
of each other. Fuel from the supply tank is passed
through a filter to the injector pump supply pipe.
The injector pump receives the fuel which is then
Low pressure pump; delivers fuel from tank to
Gear pump
injected into the cylinders in proper quantity and at
injector: fuel also lubricates the pump.
a prearranged time.
Meters, times, and pressurizes fuel: camshaft-
(3) Electronic Fuel Injection. The electronic
operated by pushrod and rocker arm; one injec-
fuel injection system is an advanced design for mod-
tor for each cylinder.
ern diesel engines, intended to produce improved
Protect machined components from dirt and
starting and operating characteristics. Several sys-
water in fuel.
tems have been developed, mainly for smaller and
Controls engine speed. Varies position of the
intermediate-sized engines. Similarities to me-
injector plunger to vary amount of fuel in-
chanical injection systems include the following: a
fuel pump (or pumps), a governor or speed regula-
tor, filters, and fuel injectors. The major difference
Table 3-2. Common rail injector system.
between mechanical and electronic systems is the
computer which replaces the mechanical compo-
nents (cams and pushrods) used to control fuel in-
Low and
Low-pressure pump delivers fuel from tank to
jection. The computer processes data inputs (such
high-pressure pump; high-pressure pump deliv-
high-pressure pump
as engine speed and load, desired speed or governor
ers fuel to injectors at the desired operating
pressure: fuel lubricates governor and pumps.
setting, engine temperature, and generator load).
Computer output is precisely timed electrical sig-
Flyweight-type; controls maximum fuel pres-
sure; prevents engine overfueling; controls en-
nals (or pulses) that open or close the fuel injectors
gine idle and prevents overspeeding by control-
for optimum engine performance. Adjustment of in-
ling fuel supply: contained within main pump
jection timing is seldom required after the initial
setup. Refer to the engine manufacturer's literature
Controlled by the operator; regulates fuel flow
for maintenance of injectors, pumps, and other fuel
and pressure to injectors.
system components.
Meters, times and pressurizes fuel; camshaft-
g. The main components of the fuel system. Fuel
operated by pushrod and rocker arm: one injec-
supply source, transfer pump, day tank, fuel injec-
tor for each cylinder.
tion pump, fuel injection nozzles, and filters and
Protect machined components from dirt and
strainers. These components are matched by the
water in fuel.
engine manufacturer for optimum performance and
warranty protection.
Table 33. In-line pumps and injection nozzle system.
(1) The fuel supply source is one or more stor-
age tanks. Each tank must have drain valves for
removal of bottom water, see paragraph 2-4 for
Meters, times, pressurizes and controls fuel
Injection pump
genera! requirements. Additionally, the fuel system
delivered to the injection nozzles; consists of
single pumping element for each cylinder; tit-
should include a day tank and a transfer pump, see
ted into a common housing; operated by rocker
paragraph 2-4d.
arm or directly from the camshaft.
(2) The follo wing paragraphs cover the fuel in-
Usually the flyweight-type: may be mounted on
jection pump, fuel injection nozzles, and filters and
main injection pump housing; controls fuel de-
livery: variable-speed or limiting-speed type is
(3) A fuel injection pump accomplishes the
functions described in paragraph 3-4b(3). Addi-
Fuel lines
High-pressure type; transports fuel from pump
tional details are provided in the following para-
to injection nozzles.
Injection nozzle
Spring-loaded; hydraulically operated valve that
(a) The fuel injection pump must perform
is inserted in the combustion chamber: one
two functions: first, deliver a charge of fuel to the
nozzle for each cylinder.
engine cylinder at the proper time in the engine
Protect machined components from dirt and
operating cycle, usually when the piston has almost
water in fuel.
reached the end of the compression stroke; and sec-
ond, measure the oil charge delivered to the injector
supplied to the cylinders by individual pumps oper-
so the amount of fuel is sufficient to develop the
ated from cams located on a camshaft or on an
power needed to overcome the resistance at the
auxiliary drive. The pumps operate independently


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