If an injection nozzle is not properly delivering fuel
into the pre-combustion chamber of a cylinder, driveability could be greatly
effected, or a DTC could be set. If other diagnosis indicates, or if the injection
nozzles are suspected of not properly delivering fuel, they should be tested.
Typically, a nozzle failure can been detected by using the injector balance
test.
Nozzle testing is comprised of the following checks:
| • | Injector Balance test (performed with scan tool). |
| • | Nozzle opening pressure (see Important statement). |
| • | Leakage (see Important statement). |
Injector Balance Test
An injector balance test is performed with the scan tool. This test
will properly identify a stuck closed or noisy injector nozzle. Typically,
a nozzle failure will fall into this criteria.
- Install scan tool.
- Start and idle engine.
- Perform injector balance test on each cylinder (balance test refer
to a specific cylinder).
If a suspect nozzle has been located, it can be swapped with the adjacent
cylinder and balance test can be repeated as a check to positively identify
a faulty nozzle.
- Locate and replace faulty nozzle and glow plug.
Nozzle Opening Pressure Test
Caution: Do not place your hands or arms near the tip of the nozzle when testing
the nozzles. The high pressure atomized fuel spray from a nozzle has sufficient
penetrating power to puncture flesh and destroy tissue. This may result in
blood poisoning. Always enclose the nozzle tip in a receptacle, preferably
transparent, in order to contain the spray.
Important: Injector Nozzle Opening Pressure and Leakage tests should only be performed
on vehicles with high mileage, engines that have been over heated or on vehicles
that pull heavy loads. False or inaccurate readings can occur if the following
tests are not performed to the above criteria.
Important: Each test should be considered independent of the others (for example,
when checking opening pressure, do not check for leakage). If all of the
following tests are satisfied, the nozzle assembly can be reused. If any one
of the tests is not satisfied, the complete nozzle assembly must be replaced.
When performing the injection nozzle tests, refer to the instructions provided
with the nozzle tester J 29075- B.
| • | Position a nozzle tester on a workbench. |
| • | Install one nozzle on the tester fitting. |
| • | Place a container under the nozzle that will deflect the nozzle
spray absorb the test fluid. |
| • | Install two clear plastic hoses (1 in. long) over the leak-off
fittings. |
| • | Close the shutoff valve at the pressure gauge. |
| • | Operate the lever of the nozzle tester repeatedly and briskly
to fill and flush the nozzle with test oil. |
- Open the shutoff valve at the pressure gage one-quarter turn.
- Depress the tester lever slowly. Note at what pressure the needle
of the pressure gage stopped. The maximum observed pressure is the opening
pressure.
| • | Some nozzles may pop while other nozzles may drip down (this is
not leakage). |
- The opening pressure should not fall below the lower limit of
105 bar (1500 psi) for naturally aspirated engines and 117 bar
(1700 psi) for turbo-charged engines for used nozzles.
- Replace nozzles which fall below the lower limit.
Nozzle Leak Test
Caution: When testing nozzles, do not place your hands or arms near the tip of
the nozzle. The high pressure atomized fuel spray from a nozzle has sufficient
penetrating power to puncture flesh and destroy tissue and may result in blood
poisoning. The nozzle tip should always be enclosed in a receptacle, preferably
transparent, to contain the spray.
Important: Injector Nozzle Opening Pressure and Leakage tests should only be performed
on nozzles with high mileage, engines that have been over heated or on vehicles
that pull heavy loads. False or inaccurate readings can occur if the following
test are not performed to the above criteria.
- Open the shutoff valve at the pressure gage (1 turn).
- Blow dry the nozzle tip.
- Depress the lever of the manual test stand slowly until the gage
reads a pressure of 95 bar (1400 psi). Observe the nozzle tip. A drop
may form on the end of the nozzle but should not drop off within a period
of 10 seconds.
- Replace the nozzle assembly if a drop falls during the 10 seconds.
