CAT 3412C - Fuel System Prime

2. Loosen each fuel line nut one at a time at the fuel
injection pump. A cloth or similar material must be
used in order to prevent fuel from spraying on the
hot exhaust components. Tighten each nut before
loosening the next nut.
3. A defective fuel injection nozzle may be identified
when a fuel line nut is loosened and the following
conditions are present:
• The exhaust smoke is partially eliminated or
the exhaust smoke is completely eliminated.
• Engine performance is not affected.
A fuel injection nozzle that is suspected of being
defective should be removed. A new fuel injection
nozzle should be installed in the cylinder in order
to determine if the removed fuel injection nozzle is
defective.
Removal and Installation of the
Fuel Injection Nozzles
For the removal and the installation of fuel injection
nozzles, special tooling is required. Refer to the
Service Manual for more information. Consult your
Caterpillar dealer for assistance.
i00891826
Fuel System - Prime
SMCS Code: 1258-548
Personal injury or death can result from a fire.
Fuel leaked or spilled onto hot surfaces or electri-
cal components can cause a fire.
Clean up all leaked or spilled fuel. Do not smoke
while working on the fuel system.
Turn the disconnect switch OFF or disconnect
the battery when changing fuel filters.
Prime the fuel system in order to fill dry fuel filters.
You must also prime the fuel system after any one of
the following conditions exist:
• The fuel system has run dry.
• The engine has been in prolonged storage.
• The fuel filter has been cleaned.
• The fuel filter has been replaced.
Note: If the engine does not have a fuel priming
pump, refer to Step 4.
1. Unlock the priming pump, and operate the priming
pump until a resistance is felt. This procedure will
probably require a considerable amount of
priming.
2. Push in the plunger, and hand tighten the plunger.
NOTICE
Do not crank the engine for more than 30 seconds.
Allow the starter to cool for two minutes before crank-
ing again. Turbocharger damage can result if the en-
gine rpm is not kept low until the oil gauge display
verifies that the oil pressure is sufficient.
3. Crank the engine.
If the engine starts and the engine runs rough, run
the engine at low idle. Continue running the
engine until the engine runs smoothly.
NOTICE
During periodic service, DO NOT remove the fuel fil-
ter plug that is in the fuel filter base in order to purge
air from the fuel system. The periodic removal of the
fuel filter plug will result in increased wear on the
threads in the fuel filter base. This wear leads to fuel
leakage.
4. Open the vent valve (if equipped) on the fuel
injection pump's housing.
5. Operate the priming pump until the flow of fuel
from the vent valve is continuous and the flow of
fuel is free of air bubbles.
If the engine does not have a fuel priming pump,
crank the engine. Crank the engine until the fuel
flows freely and until the fuel is free of air bubbles.
6. Close the vent valve. Then, push in the plunger.
Hand tighten the plunger.
7. Crank the engine. If the engine starts and if the
engine runs rough, run the engine at low idle.
Continue running the engine until the engine runs
smoothly.
Note: If the engine will not start, more priming is
necessary. If the engine continues to run rough, more
priming is necessary as well.
NOTICE
Do not let the tops of fuel nozzles turn when the fuel
line nuts are loosened or tightened.
The nozzles will be damaged if the top of the nozzle
turns in the body.
The engine will be damaged if a defective fuel injec-
tion nozzle is used because the shape of fuel (spray
pattern) that comes out of the nozzles will not be
correct.
SEBU7125-13
127
Maintenance Section
Fuel System - Prime