2.34. FAULTY ENGINE OPERATION
Trouble with the engine's operation can arise from many things. Satisfactory operation depends
upon good compression pressure and the injection of the proper amount of fuel at the right time. Loss of
compression or faulty injector action can cause lack of engine power, uneven running, excessive
vibration, and a tendency to stall when idling. The following troubles, with lists of possible causes and
remedies, are given to assist the mechanic in diagnosing engine trouble and correcting it.
a. Refuses to start. If an engine fails to start, it usually means either weak batteries or
insufficient air pressure. Loss of compression is often caused by dry pistons and a small amount of oil
should be introduced into the cylinders. If the engine still fails to start, check the fuel system for air
locks. An air lock in the low pressure pipeline can be cleared by opening the priming valve on the
pump; in the high pressure pipeline, by slacking back the delivery pipe union nut at the injector while
the engine is turned over a few times.
When poor starting gets worse, it is probably caused by valve trouble and maintenance is
the only remedy. At temperatures below 32 F., check cold weather starting aids.
b. Irregular running. Several defects can cause irregular running. Some of these are an engine
valve sticking open, dirty atomizers, air in one of the high-pressure injector pipes, a sticky fuel pump
delivery valve, and water in the fuel oil.
c. Uneven running and excessive vibration.
(1) Faulty injector timing or rack setting.
(2) Insufficient fuel supply.
(3) Hunting governor.
Remove all the bind from injector control rack operating shaft
(4) Cooling water temperature too low. Check thermostats.
(5) Valves in bad condition. Check compression pressures.