4TNV98 & 4TNE98 Diesel Engine Section 4. Fuel System
164
Testing of Fuel Injectors
CAUTION
Never use a steel wire brush to clean fuel
injectors. Damage to the nozzle and other
components is likely to result.
1. Thoroughly clean the fuel injector nozzle using
clean diesel fuel and a brass wire brush.
2. Visually inspect the fuel injectors and nozzle
protectors for deposits or damage. Clean, repair
or replace as necessary.
NOTE: Test the fuel injector using an injection
nozzle tester. Operate the tester following the
information provided by the tester manufacturer.
Use clean, filtered fuel or FIE calibration fluid for the
test.
3. Using the correct adapter, connect a fuel injector
to a nozzle tester. Aim the fuel injector into a
suitable container to catch the fuel spray.
WARNING
Never inject fuel toward you. Since the fuel is
injected at high pressure from the nozzle, it may
penetrate the skin, resulting in injury.
Never inject fuel toward a fire source. Atomized
fuel is highly flammable and may cause a fire or
burn skin.
CAUTION
FLYING OBJECT HAZARD!
ALWAYS wear eye protection when servicing
the engine and when using compressed air or
high-pressure water. Dust, flying debris,
compressed air, pressurized water or steam
may injure your eyes.
Failure to comply may result in minor or
moderate injury.
Figure 7-49
4. Pump the operating lever of the tester slowly,
observing the pressure reading at the point
where the fuel injector begins spraying fuel
(Figure 7-49).
See Figure 7-52 for injector ID location.
See Test and Adjustment Specifications on page
7-9 for correct pressure readings.
NOTE: The opening pressure of a new fuel injector
will be approximately 725 psi (5MPa; 51kgf/cm²)
higher than one that has been operated for five
hours or longer.
5. Pump the operating lever slowly to hold the
pressure steady at a point just below the opening
pressure and hold it for 5 seconds. Observe the
injector to see that it is sealing properly and is
not “dripping”. If fuel leaks from the return line
fitting, check that the nozzle case nut is tight.
Service or replace the injector if fuel continues to
leak from either the return line fitting or nozzle.
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