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Руководство по эксплуатации Страница: 18

BMW K75 [18/236] Engine does not start when turned over

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18 Fault diagnosis 1 Introduction This Section provides an easy reference guide to the more common faults that are likely to afflict your machine Obviously the opportuni ties are almost limitless for faults to occur as a result of obscure failures and to try and cover all eventualities would require a book Indeed a number have been written on the subject Successful fault diagnosis is not a mysterious black art but the application of a bit of knowledge combined with a systematic and logical approach to the problem Approach any fault diagnosis by first accurately identifying the symptom and then checking through the list of possible causes starting with the simplest or most obvious and progressing in stages to the most complex Take nothing for granted but above all apply liberal quantities of common sense The main symptom of a fault is given in the text as a major heading below which are listed as Section headings the various systems or areas which may contain the fault Details of each possible cause for a fault and the remedial action to be taken are given in brief in the paragraphs below each Section heading Further information should be sought in the relevant Chapter Note If a fault is thought to lie in the fuel or ignition systems the simplest solution may well be to take the machine immediately to an authorised BMW dealer for attention Refer to Chapter 5 or 6 as appropriate but always check all other possible causes first eg a misfire can also be caused by dirty fuel Items such as dragging brakes or under inflated tyres should not be overlooked Starter motor problems 2 Starter motor not rotating Engine stop switch off Fuse blown Check fuse number 1 located behind the left hand side panel Battery voltage low Switching on the headlamp and operating the horn will give a good indication of the charge level If necessary recharge the battery from an external source Load shedding relay faulty If the ancillary circuits are not cut off when the starter motor is operating the current drain may be sufficient to prevent the motor from rotating Renew the relay Neutral gear not selected Faulty neutral indicator switch or clutch interlock switch Check the switch wiring and switches for correct operation Ignition switch defective Check switch for continuity and connections for security Engine stop switch defective Check switch for continuity in Run position Fault will be caused by broken wet or corroded switch contacts Clean or renew as necessary Starter button switch faulty Check continuity of switch Faults as for engine stop switch Starter relay faulty If the switch is functioning correctly a pronounced click should be heard when the starter button is depressed This presupposes that current is flowing to the solenoid when the button is depressed Wiring open or shorted Check first that the battery terminal connections are tight and corrosion free Follow this by checking that all wiring connections are dry tight and corrosion free Check also for frayed or broken wiring Occasionally a wire may become trapped between two moving components particularly in the vicinity of the steering head leading to breakage of the internal core but leaving the softer but more resilient outer cover intact This can cause mysterious intermittent or total power loss Starter motor defective A badly worn starter motor may cause high current drain from a battery without the motor rotating If current is found to be reaching the motor after checking the starter button and starter relay suspect a damaged motor The motor should be removed for inspection 3 Starter motor rotates but engine does not turn over Starter motor clutch defective Suspect jammed or worn engagement rollers plungers and springs early 100 models or locking sprags all other models Note particularly that clutch may be rendered inoperable by build up of oily sludge in which case stripping and flushing out is required Modified components may be available to effect a more permanent solution Refer to Chapter 1 for more details Damaged starter motor drive train Inspect and renew components where necessary Failure in this area is unlikely 4 Starter motor and clutch function but engine will not turn over Engine seized Seizure of the engine is always a result of damage to internal components due to lubrication failure or component breakage resulting from abuse neglect or old age A seizing or partially seized component may go un noticed until the engine has cooled down and an attempt is made to restart the engine Suspect first seizure of the valves valve gear and the pistons Instantaneous seizure whilst the engine is running indicates component breakage In either case major dismantling and inspection will be required Engine does not start when turned over 5 No fuel flow to engine No fuel or insufficient fuel in tank Fuel pump faulty Check first fuse number 6 located behind the left hand side panel then fuel injection relay before suspecting pump Refer to Chapter 5 and or 10 Tank filler cap air vent obstructed Usually caused by dirt or water Clean the vent orifice Fuel filter blocked Blockage may be due to accumulation of rust or paint flakes from the tank s inner surface or of foreign matter from contaminated fuel Renew the filter and clean the pump gauze strainer Look also for water droplets in the fuel Fuel line blocked Blockage of the fuel line is more likely to result from a kink in the line rather than the accumulation of debris 6 Fuel not reaching cylinder If fuel is present under pressure in the rail but not reaching the intake port then either the injector is blocked or faulty of there is a fault in the fuel or ignition system components Take the machine to an authorised BMW dealer for testing 7 Engine flooding Flooding of the engine itself can be caused only by dirt jamming an injector open Renew the injector and clean out the fuel system An excessively rich mixture can only be caused by a fault in the fuel injection control unit although it is possible for a faulty temperature sensor to cause the control unit to carry on feeding a rich mixture to the engine when it is fully warmed up 8 No spark at plug Ignition switch not on Engine stop switch off Fuse blown Check fuse for ignition circuit See wiring diagram Battery voltage low The current draw required by a starter motor is sufficiently high that an under charged battery may not have enough spare capacity to provide power for the ignition circuit during starting Load shedding relay faulty causing same symptoms as above Renew the relay Starter motor inefficient A starter motor with worn brushes and a worn or dirty commutator will draw excessive amounts of current causing power starvation in the ignition system See the preceding paragraph Starter motor overhaul will be required Spark plug failure Clean the spark plugs thoroughly and reset the electrode gaps Refer to the spark plug section and the colour

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