Gauges provide a "look" inside the engine. Be sure they are in good working order. You can determine what is "normal" operating range by observing the gauges over a period of time. The cause of any sudden or significant change in the readings should be determined and corrected.
OIL PRESSURE - Oil pressure is normally greatest after starting a cold engine. As the oil warms up the pressure drops. Oil pressure is greater at operating speeds than at low idle. Fluctuating readings can mean air in the oil or a sticking pressure relief valve. Stop the engine immediately if a sudden loss of oil pressure occurs.
WATER TEMPERATURE - The operating temperature is maintained by the water temperature regulator. High coolant temperatures mean the cooling system is not dissipating enough engine heat.
The minimum operating temperature should not be below 175°. If the temperature gauge continues to indicate below 175° while operating, have the gauge checked for accuracy and the thermostats checked for proper operation.
In cold weather the temperature gauge may fluctuate in or near the cold range. This indicates the engine is being overcooled. In these instances the use of radiator louvers is suggested.
AMMETER - The ammeter should register in the charging range when the engine is running above low idle. If the gauge still registers a discharge as the engine speed is increased, determine the cause.
An automatic start-stop system ensures that power is supplied to a load when the normal power source is interrupted. The cranking panel is the heart of the system and consists of the failure warning system and relays to start and stop the engine. When a power failure occurs the system senses the failure, starts the engine and transfers the load to standby. When power is restored, it senses power restoration, transfers the load from standby and stops the engine. The major use of automatic start-stop system is standby electric sets. This discussion is limited to that application.
The remote contacts close when a power failure occurs and completes the circuit to the cranking timer and the start slave relay. The start slave relay completes the circuit to the starter motor and the engine begins cranking.
As the engine starts and increases in speed, the frequency sensing relay turns off the cranking timer and starts the slave relay. This disconnects the starter motor circuit and protects the starter from overspeed damage. If the engine fails to start, the cranking timer will time out and lock the start circuit open, preventing the batteries from being discharged.
During the cranking cycle, the safety shutoffs are inoperative to prevent a low oil pressure shut down. When oil pressure reaches a safe level the safety circuit is armed by the arming relay. High water temperature or low oil pressure will now stop the engine and prevent major damage.
If an unsafe engine condition exists, a sending unit completes the circuit to the safety relay and locking relay. The safety relay de-energizes the fuel solenoid and stops the engine. The locking relay insures that the circuit to the safety relay is complete even if the remote contacts open.
The safety circuit must be reset by moving the start selector switch to the OFF position. Before restarting any unit which has been shut down by the safety circuit, the cause must be determined and corrected.
Determining The Cause Of Shutdown
Anytime an engine is shut down by its safety circuit, the cause must be determined. In some cases the cause will be obvious but often an investigation will have to be made. Do not put the engine back into service without determining and correcting the cause of the shutdown.
High Water Temperature
Look for the obvious first.
- 1. Check for water on the floor from spilled or leaking coolant.
- 2. Check the water temperature gauge for accuracy.
- 3. Check air flow through the radiator.
DO NOT remove the pressure cap of an overheated unit. The coolant is under pressure and relieving this pressure will cause the coolant to flash into steam. Serious burns and engine damage can result from the escaping coolant. Pressure in a radiator or surge tank may be reduced by pouring warm water on the top tank to condense the steam.
NEVER add cold water to an overheated engine.
- 4. Check air temperature to radiator. Few radiators can adequately cool a fully loaded engine with 125°F (52°C) ambient air.
- 5. Check for recirculating air currents.
- 6. Check fan and water pump belts for proper tension.
- 7. See that engine room vents and louvers are open.
- 8. Check water hoses for leaks. Is the water pump inlet hose collapsed. Hoses have been known to peel off internally and restrict water flow.
- 9. If the engine is overloaded, overheating can result.
Overheating can cause seals and gaskets to relax and fuel nozzles to change their operating characteristics. If severe or prolonged overheating has occurred, have the engine checked.
Low Oil Pressure
Look for the obvious first.
- 1. Check the oil level.
- 2. Check floor for oil from leaks.
- 3. To determine if low oil pressure was the cause of the shut down, crank the engine with the fuel valve disconnected. If unusual noises come from the engine, discontinue cranking. If oil pressure fails to build up, and no external leaks are found, the problem is probably internal.