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Engine Control System Operation
C Series

 
The engine control system has been designed to not only start and stop the engine, but to also provide safety shut downs. The following conditions will be detected and cause the engine to stop: low engine oil pressure, high engine coolant temperature, or hot exhaust manifold temperature.
 
The oil pressure switch is mounted on the left side of the engine, looking at the hand crank end (see Parts page 2, item 5). It is normally open and will close when the oil pressure falls to the range of 12 to 18 psi.
 
The water temperature switch is located on the cylinder head (see Parts page 8, item 47). It is normally open and will close when the engine coolant temperature rises to 185 degrees F.
 
The exhaust temperature switch is located on the upper surface of the exhaust elbow (see Parts page 16, item 18). It is normally open and will close when the surface temperature of the elbow rises to 140 degrees F.
 
The control system has been designed to rest in a STATIC CONDITION OF READINESS, when it is not running. That is, it REQUIRES NO POWER to start and run the engine. A hand crank is provided as an alternative to electric start when the vessel's batteries are "dead".
 
Theory of Operation
Please refer to the Control System Schematic.
 
+12 Battery Cable: The +12 volt battery terminal is connected to the heavy terminal of the starter motor by battery type cable.
 
-12 Battery Cable: The -12 volt battery terminal should be connected to the crankcase of the engine (this is control system ground) at any convenient point; preferably at one of the starter mounting bolts.
 
Start/Stop Switch: +12 volts is taken from the starter post and applied to the rotating contact of the start/stop switch.
 
Run Position: When the start/stop switch is rotated to the run position, +12 volts is applied to the hourmeter and the alarm light. Because the engine has not started yet, the oil pressure switch is still closed, and therefore ground is applied to the alarm light through diode D2, and the alarm light is turned on. This is normal.
 
Starting the Engine: Rotating the start/stop switch to the start position feeds +12 volts through diode D3 to the alarm light, keeping it turned on, and to the start relay (located near the start motor) causing the start relay to energize. The internal heavy contacts of the start relay close and power is applied to the starter solenoid on the start motor. The start motor turns the engine over, and two things happen simultaneously. The engine starts, and the oil pump in the engine develops oil pressure, causing the oil pressure switch to open. When the oil pressure switch opens, the alarm light will go out. After the engine starts, place the rotary switch in the run position.
 
CAUTION: If the alarm lamp does not go out within 7 seconds after the engine starts, it means there is an alarm condition and the ENGINE SHOULD BE STOPPED IMMEDIATELY. Begin troubleshooting procedures.
 
CAUTION: Under normal conditions, the engine will start within 3 to 7 seconds after rotating the start/stop switch to the start position. If the engine does not start, DO NOT CONTINUE CRANKING. Begin troubleshooting procedures.
 
Alarm Light: In the run position, +12 volts is applied to the top of the alarm light. However, the light will not come on unless the oil pressure switch is closed, indicating an oil pressure problem; or one of the temperature switches is closed, indicating a problem with the cooling system.
 
Stopping the Engine: Assuming the unit operates normally, and the oil pressure is high enough to keep the oil pressure switch open, the engine can then be stopped by rotating the start/stop switch to the stop position. A momentary contact is all that is required.
 
Stop Position: In the stop position, the momentary +12 volts is applied to four places: the stop solenoid which energizes and pulls the injection pump fuel rack to the off position, the normally closed contacts HC1, the coil of relay RL1, and a contact of relay RL2.
 
Relay R1 energizes, connecting +12 volts from the battery terminal on the start motor, through RL1 contacts to the bottom contact of HC1, and from there to the stop solenoid. At the same time +12 volts is connected through the contacts of HC1 to the coil of RL1, keeping RL1 (latched) energized.
 
The closed contacts of RL1 also apply +12 volts to the heater element H1. After approximately 13 seconds, the heater element causes the contacts HC1 to open. When this happens, the +12 volts that came through the contacts of RL1, and the contacts of HC1 to the coil of RL1, keeping it energized, is disconnected, allowing R1 to de-energize. At the same time the contacts of HC1 open, the +12 volts is disconnected from the stop solenoid, returning it to the "static" condition.
 
So far, relay RL2 is not involved in the process. It is part of the emergency stop system only.
 
Safety Stops

 
Start/Stop Switch: In the run position of the start/stop switch, +12 volts is applied to the alarm light. +12 volts also comes from the battery cable terminal on the starter and connects to a contact on RL1, a contact on RL2, and the coil of RL2. As long as there is no alarm condition, relay RL2 will not energize because the ground side of the coil is not connected to ground.
 
Alarm Switches: If any of the three alarm switches has a momentary contact closure, ground will be applied to the bottom of coil RL2, through capacitor C1, and it will energize. When this happens, +12 volts will be applied through RL2's contacts to the coil of RL1, and the stop sequence begins; the same as if a manual stop had been initiated by the start/stop switch.
 
The capacitor C1 provides a momentary path for current to flow through RL2. Capacitor C1 will return to a "static" condition after 60 seconds, rearming the stop sequence for the next cycle of operation.
 
If the engine has been properly maintained, and all of the external support systems, including sea water feed, fuel feed, battery power, etc., are functioning properly, Under normal conditions, the engine will start within 3 to 7 seconds after rotating the start/stop switch to the start position. If the engine does not start, DO NOT CONTINUE CRANKING. Begin troubleshooting procedures immediately. Call Entec West, Inc. for further assistance if required.
 
Manually Stopping the Engine: If for any reason the control system will not energize the stop solenoid on the engine, the engine can be stopped manually. Apply pressure to the clevis at the end of the stop solenoid assembly and push the solenoid plunger into the solenoid body. Hold the plunger in the solenoid, for 10 to 12 seconds, or until the engine stops. Do not disconnect the solenoid from the control arm.
 
CAUTION: Do not disconnect the Engine Control System from battery power when the engine is running. The Alarm System will not operate!

 
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