check your manufacturers repair manual for proper
specifications and procedures.
Preventive maintenance is the most frequent type of
servicing you will perform on a gasoline fuel injection
system. Preventive maintenance consists of periodic visual
checks and scheduled fuel filter service. Fuel filters are of
the cartridge type, in line type, and disposable type.
All fuel injection system control sensors, such as
temperature, oxygen, manifold absolute pressure, and
so forth, (these are fully described in chapter 4 of this
TRAMAN) are electrically connected to the electric
control module (ECM). Some of these sensors, such as
the oxygen sensor, have a regular maintenance cycle.
Check your manufacturers repair manual for special
instructions pertaining to these sensors.
Be sure the air intake system is sealed properly.
Early detection will save fuel and prevent engine
damage. Air leaks are a problem to gasoline fuel
injection systems. If the air leak is after the air filter, dirt
will be ingested into the engine causing internal damage
to the engine. Air leaks that bypass temperature sensors
can cause false readings to be delivered to the ECM,
changing injection quantity. Unmetered air leaks in the
intake manifold can cause a lean fuel-air mixture to be
delivered to the combustion chambers.
During regular maintenance and always after
reassembly, you should check for fuel leaks. Gasoline
leaks, however small, arc extremely dangerous. They must
be dealt with immediately. Clean around all areas to be
disassembled. Heavy layers of dirt and grime may make
some leaks hard to find. Install new seals on leaking
connections and replace cracked or leaking hoses.
Gasoline fuel injection systems operate
with fuel pressures up to five times greater than
that of standard gasoline fuel systems. Any
replacement fuel lines used should be approved
for higher pressures. Failure to do so will result
in an unsafe fuel system on the vehicle with the
danger of possible explosion and fire.
Clean around all areas before reassembly. When you
tighten injector line nuts (injector head), use new seals
and proper torque specifications. When you tighten fuel
lines, use flare nut type of wrenches because regular
open-end wrenches may damage these fuel line fittings.
Gasoline fuel injection systems have up to eight
different manufacturers and over 21 different models. The
1990 edition of Electronic Fuel Injection (Domestic)
Diagnosis and Testing Manual by Mitchell is an excellent
source for additional study on this subject.
DIESEL FUEL INJECTION SYSTEMS
When you studied the Construction Mechanic 3
& 2, you learned about general maintenance, removal, and
replacement of diesel fuel; injection pumps, injectors,
blowers, and turbochargers, as well as timing, minor
adjustments, and repairs to the Caterpillar, International
Harvester, General Motors, and Cummins diesel fuel
systems. In this section, you will learn about the processes
used to overhaul and troubleshoot diesel fuel and air
CATERPILLAR FUEL INJECTION
There are three types of Caterpillar fuel injection
systems: the forged body, the compact, and the sleeve
metering systems. While these systems serve the same
purpose and you use common general troubleshooting
procedures, each has an individual design. These
systems have a capsule type of injector with a
precombustion chamber that conditions the injected fuel
for more effective combustion.
Forged Body Fuel System
The two main parts of the Caterpillar fuel injection
system are the fuel injection pump (fig. 5-5), which
times, meters, and creates the pressure needed for fuel
Figure 5-5.-Fuel injection pump.