Engine Maintenance
102
Engine Fuel System
TK486V25 engines use a mono-plunger and
distributor injection pump.
The components of the fuel system are:
•
Fuel tank
•
Electric fuel pump (with prefilter)
•
Fuel filter/water separator
•
Injection pump
•
Trochoid feed pump
•
Injection nozzles
Operation
Fuel is drawn from the fuel tank by the electric
fuel pump, which pushes fuel to the fuel
filter/water separator. Filtered fuel passes through
a line from the outlet fitting on the filter base to
the injection pump.
The injection pump forces the fuel, at a very high
pressure, through the injection nozzles. The
injection nozzles atomize the fuel as it is injected
directly into the combustion chambers.
Injection pump leakage, injection nozzle overflow
and excess fuel from the fuel filter orifice are then
all sent back to the fuel tank in the return line.
Fuel Line Routing
The fuel lines from the fuel tank connect to the
fittings on the fuel filter. Do not change the
factory routing of the fuel lines from the fuel filter
to the high pressure fuel pump. See the fuel line
routing diagrams in the Diagrams Chapter.
Maintenance
The injection pump is relatively trouble-free and
if properly maintained will usually not require
major service repairs between engine overhauls.
Contamination is the most common cause of fuel
system problems. Therefore, to ensure best
operating results, the fuel must be clean and fuel
tanks must be free of contaminants. Change the
fuel filter/water separator regularly and
inspect/clean the electric fuel pump filter.
IMPORTANT: Do not open the fuel system
unless required.
NOTE: The injection nozzles must be cleaned
and tested (and repaired if necessary) at least
every 3,000 hours in accordance with EPA 40
CFR Part 89. Normal conditions are considered
to be the use of clean high quality fuel, no used
oil blending, and regular maintenance of the
fuel system according to the Maintenance
Inspection Schedule. Refer to the TK482 and
TK486 Overhaul Manual TK 50136 for injection
nozzle testing and repair procedures.
Whenever the fuel system is opened, take the
following precautions to prevent dirt from
entering the system:
1. Cap all fuel lines.
2. Work in a relatively clean area whenever
possible.
3. Complete the work in the shortest possible
time.
Any major injection pump or nozzle repairs
should be done by a quality diesel injection
service shop. The necessary service equipment
and facilities are not found in most engine rebuild
shops because of the large investment required.
The following procedures can be done under field
conditions:
1. Bleeding air from the fuel system.
2. Fuel tank and filter system maintenance.
3. Electric fuel pump replacement or repair.
4. Injection line replacement.
5. Engine speed adjustments.
6. Injection pump timing.
7. Nozzle spray pattern testing and adjustment.
8. Injection nozzle testing, adjustment, and
minor repair.
9. Trochoid feed pump replacement.
