takes longer than 3 to 5 minutes to disappear a problem exist. The problems white smoke may indicate are as follows: Low cylinder compression from worn rings Scored piston or liner Valve  seating  problems Water leaking into the combustion chamber Faulty  injectors Use of a low cetane diesel fuel. Black or gray smoke generally is caused by the same  conditions—the  difference  between  the colors being one of opacity or denseness of smoke. Black or gray smoke should be checked with the engine at operating temperature of 160°F.  Abnormal  amounts  of  exhaust  smoke emission is an indication that the engine is not operating correctly, resulting in a lack of power, as well as decreased fuel economy. Excessive black or gray exhaust smoke is caused by the following: Faulty automatic timing advance unit Faulty  injection  pump Incorrect valve adjustment clearances High exhaust back pressure Incorrect fuel injection timing Faulty nozzles or injectors Improper grade of diesel fuel Air  starvation Blue smoke is attributed to oil entering the combustion  chamber  and  being  burned  or  blown through the cylinder and burned in the exhaust manifold  or  turbocharger.  Remember  always check the simplest things first, such as too much oil in the crankcase or a plugged crankcase ventilation breather. The more serious problems that can cause blue smoke are as follows: Worn  valve  guides Worn  piston  rings Worn  cylinder  walls Glazed cylinder liner walls due to use of the wrong type of oil Turbocharger seal leakage Broken rings Scored pistons or cylinder walls NOTE With the engine stopped, the condition of the pistons, rings, and liners on a two-stroke cycle  Detroit  diesel  engine  can  be  checked visually  by  removing  an  air  box  inspection cover on the side of the engine block and accessing   the   components   through   the cylinder liner ports. QUICK INJECTOR MISFIRE CHECK Listed below are several quick and acceptable checks that can be performed on a running engine to determine if one or more injectors are at fault on any type  of  engine. On four-stroke-cycle engines with a high-pressure in-line pump or distributor system, such as Caterpillar and Roosa Master, you can loosen off one injector fuel line, one at a time, about one-half turn as you hold a rag around it while noting if there is any change in the operating sound of the engine. If the injector is firing properly, there should be a positive change to the sound and rpm of the engine when you loosen the line, since it prevents the delivery of fuel to the cylinder. On an engine with the PT fuel system, a cylinder misfire can be checked by running the engine to a minimum of 160°F, removing the rocker covers, then installing  a  rocker  lever  actuator  over  an  injector  rocker lever. Hold the injector plunger down while the engine is running at low idle. This will stop the fuel flow to that injector. If the engine speed decreases, the injector is good. If the engine rpm does not decrease, replace the injector. On the two-stroke-cycle nonelectronic Detroit diesel engines, you can remove the rocker cover, then using a large screwdriver push and hold down the injector follower while the engine is idling. This action is like shorting out a spark plug on a gasoline engine, since it prevents fuel from being injected into the combustion chamber. If there is no change to the sound and speed of the engine, the injector is not firing. There 5-53