delivery and the capsule type injector valve (fig, 5-6),
which injects and atomizes the fuel.
The most likely causes of faulty fuel injection
performance are (1) air in the fuel, (2) low fuel supply,
(3) water in the fuel, (4) dirty fuel filters, and (5) low
transfer pump pressure. If, after you have checked and
corrected these conditions, the engine still does not
perform properly, check the fuel injection components.
Some of the guidelines for troubleshooting and general
test procedures used to test pumps and valves are
TROUBLESHOOTING. Before you remove
either the injector pump or injector valve from an
erratically running engine, make a simple test. Run the
engine at a speed that makes the defect most
pronounced. Momentarily, loosen the fuel line nut on
the injector pump far enough so that the cylinder
misfires or cuts out. Check each cylinder in the same
manner. If you find one that has no effect on the irregular
operation of the engine or black smoke stops puffing
from the exhaust, you have located the misfiring
cylinder. You will probably only have to remove the
pump and valve for that cylinder for additional testing.
TESTING. The Caterpillar fuel injection tester
provides a means for determining the condition of the
fuel injection pumps and valves. Before you perform
any test, be sure to study and follow the instructions in
Figure 5-6.-Capsule type of fuel injection valve assembly.
the manual for the type of testing equipment you are
Injection Pump. Clean the fuel pump thoroughly
before installing it on the tester. If any abrasive material
enters the pump, it may be carried into the discharge
collector of the tester and impair the discharge
measurement accuracy. Close the fuel pump openings
with the covers provided, holding the plunger in place.
Clean the pump thoroughly with cleaning solvent or fuel
Pumps are tested at or near (within .025 inch) the
full-load setting of the engine. If the fuel delivery
from the pump is within the limits of the full-load
setting, the pump will perform properly throughout
the full range of rack travel. The governor will
compensate for pump wear at any rack setting less
than the full-load setting.
Caterpillar fuel injection pumps have no
adjustments or replacement parts for rebuilding. If the
tester reveals that the pump is no longer serviceable,
discard the pump.
To test the injector pump, determine the plunger
diameter by inserting the portion of the plunger under
the gear into the gauge supplied with the tester. Insert
the portion of the pump plunger and gear segment into
the gauge setting of the housing of the tester, as shown
in figure 5-7. Determine the proper full-load rack setting
by referring to the rack setting charts for the engine from
which the pump was removed. After you have made the
full-rack setting (usually to the nearest .025 inch), you
also will be able to determine the number of discharge
strokes required from the pump test chart. Now you are
ready to attach the collector assembly and jar to the fuel
Figure 5-7.-Test location of various size pumps.