To keep diesel engines in peak operating condition, the operator must give careful attention to the following factors-prestart inspection, starting the diesel, securing the diesel, and operator maintenance.
Before a diesel can be started, the operator must perform a prestart inspection to ensure the engine is ready for operation. The specific inspection routine varies somewhat according to each engine. The basic procedure, however, requires the operator to inspect the engine for a sufficient supply of fuel oil, lube oil, and cooling water. The operator must also be alert for any leakage of these fluids. When replenishment of cooling water is necessary for the radiator, use clean or soft water to keep the engine water jackets and coolant circulating system free of sediment. If the engine is still hot from previous operation, do not add large amounts of cold water. Sudden cooling can crack cylinders or cylinder heads and may cause unequal contraction of the structural and working parts and lead to seizing of the pistons. When topping off batteries, use distilled water.
Accessories and drives should be inspected for loose connections and mountings. If the diesel starting system is battery equipped, check the batteries for cracks and leaks, and ensure the battery cables and vent caps are clean and secure.
As a safety precaution, inspect the fire extin- guisher for ease of removal, full charge, security, and cleanliness of valves and nozzles before starting the engine.
Diesel engines rely on some external source of power for starting. The starting mechanism may be an electric motor, an auxiliary gasoline engine, compressed air, or even a hand-cranking mechanism. Whatever system is used, the starter forces the pistons to reciprocate and compresses air drawn into the cylinders. When sufficient compression has been developed with the aid of the starter, the temperature of the air in the cylinders will be high enough to ignite the injected diesel fuel. Thus internal combustion takes place and the engine begins to crank under its own power. Once the engine has been started, the actions the operator must take are as follows:
1. Throttle the engine to normal (fast idle) warm- up speed. The diesel should not be permitted to slow idle for any appreciable length of time because this causes the engine-driven blower to deliver an insufficient amount of air for complete combustion. This condition results in partially burned fuel oil, forming heavy carbon deposits that foul the valves, the piston rings, and the exhaust system.
2. Immediately check the lube oil pressure gauge. If the gauge does not indicate positive and sufficient lube oil pressure within 30 seconds, stop the engine immediately and report the difficulty to the proper authority.
3. Observe the temperature gauge during the warm-up period. The engine must not be placed under load until it reaches the proper warm-up temperature. Placing a cold engine under full load can result in serious damage to the engine because of poor lubrication at low temperature and uneven rates of expansion.
While the engine is in operation, other inspections and checks are required, such as checking of lube oil and fuel oil levels, filters and strainers, accessories and drives, and engine operating temperatures and pressures. Normally, the operator records the results of these inspections in an operating log.
When the diesel is secured, if the engine installation permits, let the engine low idle without load for a short time before stopping to allow for a gradual reduction of engine temperature. Once the diesel has been shut down, the standby lube oil pump should be kept in operation for a short time to allow the lube oil to further cool the engine. The cooling water should also be kept circulating for 15 to 30 minutes to bring the working parts to a low temperature without danger of distortion from one part cooling faster than another.
While the engine is cooling, the operator must check to determine the need for adjustment, for repair, and for replacement or renewal of parts. The required actions are as follows:
Check the fuel, the oil, and the water as in the prestart inspection.
Check the engine instruments or the gauges for proper readings.
Check the accessories and the drives as in the prestart inspection.
Inspect the air cleaners and the breather caps.
Inspect the fuel filters.
Inspect the engine controls and the linkage.
Inspect the batteries as in the prestart inspection.
Inspect all electrical wiring, insulation, and security of connections.Continue Reading