If a diesel engine is difficult to start and operates with the engine temperatures lower than normal, you should suspect that the （）.

If the water level dropped rapidly in the expansion tank of a closed diesel engine cooling water system, you should suspect a （）.

When fuel oil has seriously contaminated a diesel engine lubricating oil, you should （）.

To determine if the lube oil filter elements need changing, （）.

Electrically operated safety devices on auxiliary diesel engines function to stop the engine by （）.

The ability of the governor to prevent fluctuations in engine speed is termed （）.

The function of diesel engine piston compression rings is to （）.

The minimum speed an engine must attain before ignition can occur depends upon （）.

The main purpose of the piston oil scraper rings is to （）.

Combustion knock can occur in the cylinders of a diesel engine under any condition permitting （）.