pump, as shown in figure 5-8. Remember, bleed the air
from the pump and the collector assembly during the
priming. After the priming, remove the collector jar and
drain. Reset the counter to zero and attach the collector
jar to the collector assembly. Operate the pump the
prescribed number of discharge strokes. Remove the
collector jar and place it on a level surface. The fuel level
in the jar is to read from the bottom, as shown in figure
The condition of the pump is indicated directly by
the calibrations on the collector jar. If the fuel level is
within or above the GOOD range, the pump is
equivalent to a new one. A fuel level within or below the
POOR range shows that the pump plunger and barrel
have worn so much that the engine will be hard to start
and may have less power. Such pumps should be
Figure 5-9.-Correct level in collector jar.
Capsule Type Injector Valve. Capsule type fuel
injection valves can be tested on the fuel injection tester
for spray characteristics valve opening pressure, and
leakage rate. Before testing the valve, inspect the screen
filter. (See fig. 5-2.) If the screen is broken or clogged
with the dirt particles, discard the valve.
After inspecting the valve screen filter and cleaning
the injector valve nozzle, test the valve for spray
characteristics. A solid stream of fuel with little or no
atomization is caused either by a gummy carbon
accumulation or a particle of foreign material.
If the fuel emitted is properly atomized and the
cutoff is sharp with no dribble, the spray characteristics
of the valve are satisfactory.
When cleaning thc deposited carbon from the
injection valve nozzle (fig. 5-10), use a drill from the
cleaning tool group kit, furnished by Caterpillar, that
corresponds to the orifice size of thc nozzle. The orifice
size is usually stamped on thc side of the valve.
Next, test the valve for opening pressure and
leakage. Valve opening pressure ranges from 400 to 800
psi, as registered on the test gauge. If the injection valve
fails to reach a minimum of 400 psi, observe the gauge
to note any drop in pressure. If the pressure falls more
than 100 psi in 30 seconds, discard the injection valve
NEVER clean the injection valves with a
wire brush. The use of a wire brush to remove
carbon from the injection valves might damage
the orifice and reduce power output.
Compact Fuel System
The pressure type of compact fuel system has a
separate injection pump and injection valve for each
cylinder. Fuel is injected into a precombustion chamber
(fig. 5-11). A transfer pump delivers filtered fuel to the
manifold from which the injection pumps get their fuel.
The transfer pump supplies more fuel than is required
Figure 5-10.-Cleaning capsule type of nozzle.
Figure 5-8.-Collector assembly and jar.