Normally the injectors are controlled by EMDEC and deliver very precise amounts of fuel. If the injector is faulty, there will be a noticeable change in engine performance. Injectors can fail in several different manners, but all will impact cylinder power levels. Some of the more common failure modes are:
0 failure of the energizing coil (open or shorted) will cause a complete failure of
injection as the poppet valve will not seat to build pressure for injection. 0 a faulty poppet valve (stuck or leaking) will not allow the pressure to build for
injection, or if stuck closed, will not allow the injector to fill below the plunger.
0 a leaking or badly worn assembly will lead to low injection
pressures and poor performance.
0 if the injector tip, spring, needle, or check are damaged, the injector
Performance will be severely affected. Problems in this area are identical to the problems found on the older mechanical injectors.
Injector problems can be isolated and identified by two methods. Using the laptop computer, all injector response data can be monitored and a cylinder cutout test can be performed. Cut out the injectors one at a time with the computer and note engine response. If a good injector is cut out, there will be a slight change in engine sounds and the fuel delivery rate will be adjusted on all other injectors to compensate. If a faulty injector is cut out, there will be no change to engine sounds, speed, or injector delivery rates. This test is similar to performing the test on older systems.
Injection Control Problems (EMDEC)
When troubleshooting a control problem it must be determined: (1) if there is a true fault; (2) is the related to a software problem; or (3) is the problem due to a failure of an EMDEC component or associated wiring or other hardware. It helps to follow a set routine and logical order of checks when trying to isolate a problem. Verify all simple conditions first and use the control computer and laptop to help diagnose the problem
.
0 check the fault archive in the
EMDEC
control unit to verify the system failure.The computer may provide an indication of the cause of the failure such as the
communication between control units, communication the control unit to the injectors, or the failure of a control unit itself.
3
Before attempting to start an engine that is new, remanufactured, or has been shut down for more than 48 hours, engine is to be petformed. This procedure is described in Chapter 6 of this text.
0 check the level of fuel in the tank.
0 check condition of the filters by means of the bypass gauge located by the
primary fuel filters.
0 change all fuel filters and clean or replace the suction strainer.
0 visually examine all piping and hoses for leakage or restrictions.
0 determine whether the problem is actually low pressure, or an incorrect reading by the pressure transducer. Fit a mechanical gauge to the pressure sensor location using a "Tee" fitting. When the engine is operating, the gauge and the reading indicated by the sensor should be within a few pounds of each other.
If
not, replace the sensor with a qualified unit. If the mechanical gauge indicates a true low pressure situation, the procedures for qualifying the system remain the same as in the past.Engine
Procedure
Check levels of engine oil, governor oil, compressor oil, and engine coolant.
Open cylinder test valves and bar engine over at least one
revolution. While closing test valves, watch for discharge of fuel, engine oil, or engine coolant. If any of these are found, determine the cause and make the required repairs.
Remove the starting fuse. Check that all fuses are present and in good condition, and of the proper rating.
that the main battery switch is closed, and that the ground relay switch is
Place the local control and the control circuit breakers in the ON position.
Place the control and fuel pump switch in the ON position.
Place generator field and engine run switches in the OFF position.
isolation switch to the START position.
,
.
.
.
At the equipment rack in the engineroom, place the Fuel Start
switch in the
PRIME
position until fuel flows in the return fuel sight glass clear and free of bubbles.Check that the starting fuse is in good condition and proper rating then install it.
CAUTION:
Do not crank the engine for more than 20 seconds or "inch" the engine with the starter. After cranking allow a minimum of two minutes for starter cooling
before another start.
If engine is equipped with purge control system, do not push injector rack control lever (layshaft) until engine has cranked for six seconds.
Position layshaft at about one third rack (1.6 on the scale), then turn the Fuel Start switch to the START position. Hold the switch in the
START position until the engine fires and speed increases.
Release the layshaft when the engine comes up to idle speed.
Check that the low water detector is not tripped. If the detector is tripped, wait for one half minute after engine start, then press the reset button and hold for five seconds to reset. If the detector trips again, verify engine oil pressure, then slowly push the layshaft in to increase engine speed momentarily before resetting the button.
Check that the cooling water level, lube oil pressure, and governor oil level are all satisfactory.