TP-6805 8/15 63Section 5 Troubleshooting
Section 5 Tr oubleshooting
5.1 Introduction
Corrective action and testing in many cases requires
knowledge of electrical systems and electronic circuits.
Testing and service must be performed by an
authorized distributor/dealer or trained service
technician.
Refer to the engine service manual for engine service
information. See the List of Related Materials for the
document part number.
If the troubleshooting procedures in this section identify
a failed part, refer to the parts catalog for replacement
part numbers. See the List of Related Materials in the
Introduction for the parts catalog number.
5.2 Theory of Operation,
Electronic Start Sequence
The following steps trace the electronic system as
different leads and components are energized during
the start sequence. A start signal can come from any of
the following:
D Pressing the Run button on the RDC2 or DC2
controller
D A remote start signal through RBUS (from an RXT
transfer switch, for example)
D Closing a contact across engine start connections 3
and 4 (remote start/stop switch or non-RBUS transfer
switch engine start signal)
D A start signal over Ethernet from OnCue Plus
The start signal begins the series of events that adds
fuel, ignition, and engine crank to the start sequence.
Use the steps below and refer to the wiring schematics
in Section 8 to assist with troubleshooting and checking
for loose connections or damaged leads.
1. Engine Crank
a. When the start signal is received, the RDC2 or
DC2 controller energizes FP and lead 71.
b. FP provides 12VDC to flash the rotor field.
c. Lead 71 energizes the starter relay.
d. The starter relay closes the starter relay contact
which energizes the start solenoid.
e. The start solenoid closes and energizes the
starter motor, which cranks (turns) the engine.
f. The engine rotation and field excitation
produces alternator voltage.
2. Fuel and Ignition
a. When the RDC2/DC2 controller detects
acceptable alternator voltage (leads 11 and 44)
or frequency (leads 55 and 66), the RDC2
controller energizes lead 70 and removes the
ground to the ignition (plug 1, pin 16).
If acceptable voltage or frequency is not
detected within 3 seconds, the cranking cycle
terminates and crank pause begins.
b. Lead 70 energizes run relay P17 (if equipped),
sending 12 VDC to the fuel valve and ignition.
Fuel flows to the carburetor and the ignition
produces spark.
c. When the RDC2 controller senses alternator
voltage in winding 55 and 66, the RDC2
controller governor circuit sends 12 VDC to the
stepper motor through leads 1A, 1B, 2A, and
2B.
d. The stepper motor actuates the throttle arm on
the carburetor, allowing fuel to enter the engine.
e. When the controller senses that the engine has
reached 750 RPM (12.5 Hz), the RDC2
controller will drop power to lead 71, ending the
start sequence.
3. If running speed is not reached within 15 seconds,
the cranking cycle terminates and a crank pause
begins.
4. If the engine does not start successfully after 3
crank cycles, an Overcrank fault occurs.
5.3 Initial Checks
When troubleshooting, always check for simple
problems first. Check for the following common
problems before r eplacing parts:
D Loose connections or damaged wiring.
D Dead battery.
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