Woodward 723PLUS Technical Manual page 101

Manual 26482
Symptom Cause
Engine will not stabilize. 6. Poor engine speed
Control may be erratic or signal.
vary with load.
[continued]
7. Engine fuel delivery or
other mechanical problem.
8. Improper wiring and
installation. Possible
shielding or ground loop
problems.
Woodward
723PLUS Digital Marine Control
Test/Remedy
6a. MPU speed signal problem. Verify MPU probe is in good
condition (free of dirt, oil, grease, or metal filings). Verify the
gear is in good condition (no missing teeth, gear run out with
tolerance, etc.). If possible view speed signal to 723PLUS
control with an oscilloscope. MPU speed signal should be a
sine wave with a relatively fixed amplitude. There should be no
major wave form distortions.
6b. Possible engine firing torsionals or flexible coupling
torsionals. Attempt to re-adjust the inertia factor and/or speed
filter.
7. Attempt to isolate engine and governors. If possible, slowly
reduce mechanical load limit until actuator terminal shaft is
controlled by load limit setting. The fuel rack can also be
blocked by using the maximum fuel limiter in the 723PLUS
control.
Do not lower load limit rapidly or any lower than
necessary to prevent unwanted engine shutdowns under
severe load conditions. This is especially true at low
speed. If the engine is still unstable when the actuator/fuel
rack is blocked, the problem is most likely an engine
problem.
8a. Verify all shields are grounded at 723PLUS control only
and not at any other points. Verify shields are carried
continuously through any terminal blocks throughout their
length.
8b. If possible begin to remove one input wiring section at a
time until stability is corrected. Remove as many inputs a
possible until only the minimum connections (power supply,
MPU, & actuator) exist. An external current or voltage source
may be needed to simulate input signal when the field device
wiring is removed to run the engine. Correct the possible
ground loop, shield problem. See 8c below.
8c. Verify 723PLUS control wiring (power supply, MPU,
actuator, etc.) is not routed through conduit containing high
voltages or currents. Route suspect wiring outside of conduit
and verify engine instability goes away.
8d. If 723PLUS control wiring is isolated down to power supply,
MPU, and actuator, check condition of solder joints at MPU
and actuator connectors. Check all terminal connections for
tightness.
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