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Diesel_Engine_Service_Tips.pdf

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DIESEL_ENGINE_SERVICE_TIPS
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DIESEL INJECTION SERVICE TIPS 3 4 5. 6 7 8 9 10 11 W ear safety glasses when working on a diesel injection system. When in doubt, refer to a service manual for the make of vehicle being serviced. The slightest mistake could upset engine performance or cause engine damage. Always cap lines or plug fuel end fittings to prevent entry of foreign matter. Never drop a diesel injector or injection pump. They can be damaged. Remember that high pressure inside a diesel injection system can cause serious injury. Some diesel injection systems must be bled (air removed) after repairs. Clean around fittings before they are disconnected. Adhere to all torque specifications. This is extremely all the more important on a diesel engine. Never use a bent, frayed, or kinked injection line. Place a screen mes h over the air inlet when the engine is to be operated without the air cleaner. Rags and other objects can be sucked into the engine. Also, do not cover the air inlet with your hand with the engine running or injury may result. Check fuel filters and water separators periodically. Water can cause extensive corrosion of injection system parts. This I S one In a senes of ENEPCON Driver Energy Efficiency Tips for car owners and auto mechanics rhrs serves presents basrc rnformatron on techniques for rncreasrng fuel effrcrency in vehicles For further Information contact, Fuel Efficiency In Road Transport Sector Project, ENERCON Buildrng, G-5/2, lslamabad I I DRIVER 0 ENERGY EFFICIENCY TIPS DIESEL ENGINE DIAGNOSTICS Most diesel engine problems are related to the injection system. As such diagnosing diesel engine problems requires knowledge o f engine and injection system operation NU ” This brochure provides you with the guideline to troubleshoot various diesel engine and injection system problems. _ -- L==z;Ef,;,- g&_ -_===_= T = E ----- -_=I==< === --- -- ==___ = __= ss_-_ F WI ENERCON ENERCON Building, G-512, Islamabad, Pakistan Tel: + (92-51) 9206005, 9207572 Fax: + (92-51) 9206003 E- Mail: root@enercon.sdnpk.undp.org Designed & Printed by SAFTS Ph: 821300 A Global Environment Facility ( GEF ) Project3. ENGINE MISSING A diesel engine miss results from one or more cylinders not burning fuel properly Thi s is caused by injection system problems which include: . Faulty injectors . Clogged fuel filters . Incorrect Injection timing . Low engine compression . injection system leaks . Air leaks . Faulty injection pump 4. HARD STARTING If diese l engine does not start it may be due to- . In-operative glow plugs . Restricted air or fuel flow . Bad fuel flow solenoid l Contaminated fuel . Injection pump problem . Low battery power A slow cranking speed is a common cause for starting problem . Being a compressio n ignition engine, a diesel engine must crank fast enough to produce sufficient heat for combustion 3. LACK OF POWER Lack of engine power may be caused by . Slack throttle cables . Incorrect governor settings . Clogged fuel filters . Dirty air filters . Low engine compression . Other factors affecting combustion 6. POOR FUEL ECONOMY Poor fuel economy may be due to: . Fuel leak . Dirty air filter . Corrected injection timing . Leaking injectors 7. FUEL LEAKS Leaking fuel lines or loose connections can adversely affect the performance of a diesel engine Pinpointing exact locations of fuel lea k become much more easier when th e engine is on Since fue l is injected a t high pressure extra car e must be taken as the leaking fuel can cause serious injury If signs of fuel leakage are detected use a piece of cardboard to find the leak , move the cardboard around each fitting. If ther e is a serious leak, it will strike the cardboard and not your hand. thereby avoiding serious injury to your hand 8. CLOGGED FUEL FILTERS Other than th e main filter installe d in the fuel line for draining water, diesels have soc k filters fltted I n the fuel tank and some times in the injector assembly as shown below For optimum performance these filters must be keot cleanDIESEL TESTS DIESEL INJECTOR SERVICE Diesel Compression Test Diesel engine compression test is similar to compression test for petrol engine. I n diesels compression pressures are in the range of 3.0001 4 500 psi Readings I ” eac h cylinder should b e in the range of 50 to 75 psi of each other Cylinder-Not-Firing Test The resistance of each glow plug increases as the cylinders fire A no change in the resistance of any particular cylinder’s flow plug will show that the cylinde r I s NO T firing Pyrometer, a temperature sensing device can be used to detect temperatures at exhaust of eac h cylinder to confirm the NOT firing cylinder Injection Pressure Test An injection pressure test uses special valves and high pressure gauge to test the following, . Injector openin g pressure . Injector nozzle leakage . injection line pressure balance . Injection pump condition Due to the verstality of this tester it helps in quickl y quickly locating bad nozzle ed injector filter or faulting Pump. Most diese! engine problems are associated with the injection system . Major injector system components have bee n dlscussed in driver energy tips No 4 titled “Understanding and Maintaining Diesel Vehcles” In th e followin g section lnformation is provlded on the prope r functional characteristics of the diesel injector Injector Opening Pressure Typical diesel Injector opening pressure is approximately 1,700 to 2,000 psi (pound per square inch) of opening pressure is not wIthin service manual specifications, rebuild or replace the injector Injector Spray Pattern Some diesel injectors make chattering sound during operation while others do no:. However. all nozzles should make a swishin g or pinging sound when spraying fuel A s shown above there should be a “arrow, cone shaped mist of fluid. A solid stream of fuel, uneven spray, excessively wide spray or spray filled with solid droplets indicates that the injector needs service and / or replacementDIESEL ENGINE DIAGNOSTICS Diesel engine problems that are most frequently encountered may be identified as follows 1 Excesive Exhaust Smoke 2. Engine Knocking 3 Engine Missing 4 Hard Starting 5. Lack of Power 6. Poor Fuel Efficiency 7 Fuel Leaks 8 Clogged Fuel Filters These potential problems are briefly discussed below. 1. EXCESSIVE EXHAUST SMOKE Excessive diesel smoke is due to incomplete combustion, normally caused by faulty injection system or other engine troubles A small amount of exhaust smoke is normal during Initial start-up or rapid acceleration Type of Smoke Abnormal Exhaust smoke may be black, white or blue. Each type of smoke indicates engine problems and these are discussed below: Black Smoke Excessive black smoke is caused by a rich air-fuel mixture. This may result form problems with the lnjection pump or injection timing which may in turn be due to a choked air cleaner, worn fuel injectors, adulterated diesel fuel or the engine itself White smoke occurs mainly during cold starts. when the fuel tends to condense into liquid and does not burn due to cold engin e parts. The most common reason for white smoke are in-operatlve glowplugs low engin e compression, a bad ,n,ector spray pattern late in~ectlon timing or InJection pump problems Blue Smoke Excessive blue smoke indicates problems from low eng,ne compressio n and/o r worn piston r,ngs. scored cylinder walls or leaking valve stem seals The blue smoke is caused by crankcase 011 entering the :ombustlon chamber and being elnltted after partial combustion through the exnaust 2. ENGINE KNOCKING All diesel engines produce a “knocklng ” sound when iunn,ng In a diesel engin e fuel lgnltes when Injected unto the eomoustlo n chamber. This rapid combustion produces very high pressures generatin g a rumble or dull clattering sound. Abnormally loud “knocking” may ae due to mesel engin e miss

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