Starter motor troubles can be traced for the most partto the commutator, brushes, or insulation. If motors areto function properly, they must be kept clean and dry.Dirt and moisture make good commutation impossible.Dirty and fouled starter motors may be caused by failureto replace the cover band, by water leakage, or by excesslubrication.Most starter motors have a cover to protect thecommutator and windings. If you neglect to replace thecover or remove it as an aid to ventilation and cooling,dirt and water are sure to damage the equipment.Although lubrication of bearings is essential forproper operation, excessive lubrication may lead totrouble in a starter motor. Excess lubricant in the shaftbearings may leak or be forced past the seal and foul theinsulating material, commutator, and brushes. Thelubricant prevents a good electrical contact between thebrushes and the commutator, causing the commutator tospark and heat and the brushes to burn.Burned brushes are another possible source oftrouble if the starter motor is inoperative. Burning maybe caused by loose brush holders, improper brush springtension, a brush stuck in the holder, a dirty commutator,improper brush seating surface, or overloading thestarter.STARTER MOTOR OPERATES BUT DOESNOT CRANK ENGINEIf the starter motor and battery are in good operatingcondition but the starter fails to crank the engine, thetrouble will usually be in the drive connection betweenthe motor and the ring gear on the flywheel. Troubles inthe drive assembly are usually in the form of brokenparts or a slipping clutch (if applicable). A slippingclutch may be the result of the engine not being free toturn or of the clutch not holding up to its rated capacity.Even though seldom encountered, a stripped ringgear on the flywheel may be the source of trouble if thestarter motor does not turn the engine.ENGINE CRANKS BUT FAILS TO STARTStarting troubles and their causes and correctionsmay vary to some degree, depending on the particularengine. If the prescribed prestarting and startingprocedures are followed and a gasoline engine fails tostart, the source of trouble will probably be improperpriming or choking, a lack of fuel at various points inthe system, or a lack of spark at the spark plugs.Improper priming may be either underpriming oroverpriming. Priming instructions differ, depending onthe engine. Information on priming also applies toengines equipped with chokes. A warm engine shouldnever be primed. Some engines may require no primingexcept when they are started under cold weatherconditions.On some installations, underpriming can bechecked by the feel of the primer pump as it is operatedOn other installations, underpriming may be due toinsufficient use of the choke.Over-priming is undesirable because it results in aflooded engine and makes starting difficult. It alsocauses excess gasoline to condense in the intakemanifolds, run down into the cylinders, wash away thelubricating oil film, and cause pistons or rings to stickYou can determine flooding by removing andinspecting a spark plug. A wet plug indicates flooding.If you find the engine to be flooded, be sure to dry outor deflood it according to prescribed instructions. Someinstallations specify that the ignition switch must be ON,while others state the switch must be OFF; therefore itis important for you to follow the engine manufacturer’sinstructions.Improper carburetion may be the source of troubleif a gasoline engine fails to start. On some engines acheck of the fuel pressure gauge will indicate whetherlack of fuel is the cause. If the gauge shows theprescribed pressure, the trouble is not lack of fuel; if thegauge shows little or no fuel pressure, you should checkthe various parts of the delivery system to locate thefault.In some installations, you can determine whetherthe trouble is in the gauge or in the fuel system by usingthe following procedure: (1) remove the carburetor plugnext to the fuel pressure gauge connection; and (2) usea suitable container to catch the gasoline, and operatethe pump used to build up starting fuel pressure. If fuelis reaching the carburetor, gasoline will spurt out of theopen plug hole; this indicates that the gauge isinoperative. If no fuel flows from the plug opening, thetrouble is probably in the fuel system somewherebetween the fuel tank and carburetor. Even though allinstallations do not have a fuel pressure gauge, theprocedure for checking the fuel system is much thesame.If a wobble pump is installed to build up starting fuelpressure, you can determine whether the pump isoperating correctly by the feel and sound of the pump.If the pump feels or sounds dry, the trouble is between3-44
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