This type of trouble seldom occurs if proper installation and maintenance procedures are followed. When a part of an engine exhaust system is restricted, there will be an increase in the exhaust back pressure. This may cause high exhaust temperatures, loss of power, or even stalling. An obstruction that causes excessive back pressure in an exhaust system is generally associated with the silencer or muffler. The manifolds of an exhaust system are relatively trouble-free if related equipment is designed and installed properly. Improper design or installation may cause water to back up into the exhaust manifold. In some installations, the design of the silencer may cause water to flow into the engine. The source of water that may enter an engine must be found and eliminated. This may require replacing some parts of the exhaust system with components of an improved design or may require relocating such items as the silencer and piping. Inspect exhaust manifolds for water or symptoms of water. Accumulation of salt or scale in the manifold usually indicates that water has been entering from the silencer. Turbochargers on some engines have been known to seize because salt water entered the exhaust gas turhine from the silencer. Entry of water into an engine may also be detected by the presence of corrosion or of salt deposits on the engine exhaust valves. If inspection reveals signs of water in an engine or in the exhaust manifold, take steps immediately to correct the trouble. Check the unit for proper installation. Wet-type silencers must be installed with the proper sizes of piping. If the inlet water piping is too large, too much water may be injected into the silencer. There must be continuous-type water drains on the silencer. If a silencer has no continuous drain and if the engine is at a lower level than the exhaust outlet, water may back up into the engine.

Dry-type silencers may become clogged with an excessive accumulation of oil or soot. When this occurs, exhaust back pressure increases, causing troubles such as high exhaust temperature, loss of power, or possible stalling. A dry-type silencer clogged with oil or soot is also subject to fire. Clogging can usually be detected by fire, soot, or sparks coming from the exhaust stack An excessive accumulation of oil or soot in a dry-type silencer may be due to a number of factors, such as failure to drain the silencer, poor condition of the engine, or improper engine operating conditions.

Insufficient Intake Air

Insufficient intake air, which may cause an engine to stall or stop, may be due to blower failure or to a clogged air silencer or air filter. Even though all other engine parts function perfectly, efficient engine operation is impossible if the air intake system fails to supply a sufficient quantity of air for complete combustion of the fuel.

CLOGGED AIR CLEANERS AND SILENCERS. Sometimes an engine will fire erratically or misfire because of a clogged air cleaner or silencer. Air cleaners must be cleaned at specified intervals, as recommended in the engine manufacturers technical manuals. A clogged cleaner reduces the intake air, thereby affecting the operation of the engine. Clogged air cleaners may cause not only misfiring or erratic firing but also such difficulties as hard starting, loss of power, engine smoke, and overheating.

When you clean an air cleaner element, if you use a volatile solvent, be SURE the element is dry before you reinstall it on the engine. Volatile solvents are excellent cleaning agents but, if permitted to remain in the filter, may cause engine overspeeding or a serious explosion. Oil-bath type air cleaners and filters cause very little trouble if serviced properly. Cleaning directions are usually given on the cleaner housing. The frequency of cleaning is usually based on a specified number of operating hours, but more frequent cleaning may be necessary where unfavorable conditions exist. When you fill an oil bath-type cleaner, follow the manufacturers instructions. Most air cleaners of this type have a FULL mark on the oil reservoir. Filling beyond this mark does not increase the efficiency of the unit and may lead to serious trouble. When the oil bath is too full, the intake air may draw oil into the cylinders. This excess oil-air mixture, over which there is no control, may cause an engine to run away, resulting in serious damage.