yjetion System a 155 Diesel engine, only the air is sucked and compressed inside the cylinder. At the end of compression. ry the diesel oil is injected by an injector in.the compressed air, which ignites due to the heat of fuel at a comparatively low ed is na seks {jon and gives power impulse tothe piston, The fuel pump delive ure to the injector. Every cylinder is fitted with an injector, The quantity of the fuel to be inject g “rolled by the injector. If less fuel is injected, less power will be developed and the engine will run con lowly: ih an effective compression ratio of 14 : 1, initial temperature of 60°C and assuming true a WW pression the resulting temperature at D.C. would be 675°C. These conditions would be approximately oraned at full load and full speed. This temperature of 675°C is more than sufficient to ignite Diesel fuels, atyich have self-ignition temperatures in air at atmospheric pressure ranging from 350°C to 450°C. rig. 154 shows layout of fuel system for distributor type injection pump for a four-cylinder diesel engine. = BACK LEAKAGE PIPE LEAK OFF PIPES INuecToRs f tl Ith Vv | pete HA t 7 tit it It =|) rer cork HAND PRIMER TER “S INJECTION PUMP. Fig, 15.4 (o).Fuel system of diesel engine FUEL FILTER INJECTION NOZ2LE- (SHOLE-TYPE) FUEL PRESSURE RELIEF VALVE IN-LIN 'NJECTION PUMP. ‘SEDIMENTOR: Fig. 15.4 (b) Fuel system of direct injection SL engine for Swaraj Mazda vehciles.. a 158 Automobile Engineering Itisusing the gravity fuel tank, In this arrangement, the fuel tank must be atleast 30 cm above the fuel filters and injection pump. When the fuel cock is opened, the fuel flows direct to a hand lever type of fuel priming pump, from which it then passes out to the inlet side of the main fuel filter. The fuel after being filtered proceeds to the inlet side of the fuel injection pump. From the injection pump, it flows under high pressure in the four fuel feed pipes leading to the fuel injectors. Bach injector has a leak-off fuel pipe to carry offany back leakay is back leakage fuel is returned to the fuel tank, together with any back lea tion pump unit fuel from the nozzle valve and guide members. kage from the distributor inj Where gravity tank feed is not used in the system, a fuel feed pump is used to supply the fuel to the filter and injection pump. The fuel feed pump is usually operated by a special cam on ignition pump’s camshaft, so that both the feed and injection pumps form a single unit. NOZZLE AND HOLDER ASSEMBLY TIMING DEVICE FUEL FILTER GOVERNOR INJECTION PUMP FUEL SUPPLY PUMP. Fig. 15.5. Fuel injection equipmen for diesel engine with in-line injection pump, ,Fig, 15.6. Fuel tonk, Fig. 15.7. Fuel filter. 155, INDUCTION AIR SILENCER tration air silencer i used to minimize the noise created due to the pulsating flow of air through the vation system. The slleneet may be filed nies with the air cleaner. Sometimes, a combined air impor and sifencet is also used: Low pass fYPS of silencer eliminates all noises above certain critical enences, A small fesonalor chamber may be incorporated to eliminate high frequencies such as inuretor hiss. ‘Tunied resonator silencers generally have one large chamber of open throttle low. fequncy rat, Very high frequencies may be dealt with by a sound absorbent pad mounted in the top of the cleaner. LEAK OFF LEAK OFF ‘CONNECTION coven RUSH ‘SCREW FILTER BODY FUEL. Le FUEL 2 ee ash TI RUBBER il mim = FILTER. | asin} ELEMENT q l SPRING Pree RUBBER. Net PACKING BOWL MICRO PAPER CENTER BOLT INSERT Fig, 15.9. Poper filer assembly: Fig, 15.8. Filter assembly.158 —_— 15.6, DIESEL FUEL FILTERS Dirt carried in the fuel is recognised as a trouble and inefficiency in diesel engine operation, as it is the cause of wear in the fuel injection pump and nozzles. The fuel injection pump is a sturdy, well designed piece of equipment that will give trouble-free service for many thousands of hours running, provided the fuel is clean, but if dirt, especially fine dust, is allowed to pass into the system in the fuel, then wear follows with it irregular running and loss of power ; maintenance costs will become heavy and engines will need frequent attention. Where sedimentation in the supply tank can be efficiently carried out, this will greatly reduce the amount of dirt carried in the fuel. Under working conditions, however, itis absolutely essential that the fuel be properly filtered before entering the injection pump. Method of Operation. The fuel enters the filter bowl through the inlet connection, then passes through the filter element and leaves the filter through the outlet ime source of tonic ning ‘AB. VENTING SCREWS = cuameins its ios, as = iT Ce Sah fuses y i GASKET Soren Vases CENTRE ‘SPRING SUPPORT WASHER WITH FELT GASKET DRAINPLUG = gutter Fig. 15.10. Fuel oil filer with micro (paper) filter element. orifice completely clean. In multi-stage (dual) filters, the fuel oil flows first through the primary filter and then through the secondary micro filter before continuing to the fuel injection pump. Prior to putting into operation or after cleaning and changing of the filter element the filter must be filled with fuel oil through the filler plug orifice on the filter cover. After filling, the filler plug should be replaced immediately and the filter air vented. ‘SCREWS GASKET: PAPER ELEMENT. (MICRO FILTER) Bow! CLAMPING NUT FILLER PLUG = FELT WASHER CENTRE BOLT FELT TUBE CARRIER (PERFORATED) ‘SHEET METAL) FELT TUBE ELEMENT (COARSE FILTER) Fig. 15.11. Two-stage (Dua) Filter with flt-tube Primary and Micro (paper) Secondary fier element. The importance of care in replacing the element, avoiding getting dirt on the clean side of the filter, canno be over-emphasized, as many complaints of fuel pump element wear can be traced to lack of care in the servicing of filters. When choking takes place, this is usually found to be due to a waxy sludge which it deposited from the fuel. If filters are found to choke in an unreasonably short time this will probably poitt to an unsatisfactory fuel supply or storage tank installation ; and should be taken to find out how and @ what point an undue amount of impurities can enter the system. ae cre STEM © ‘© GROUP 3 : FUEL SsFuel Injection System is Paper elemen alocichis bas Kept fatded to be cleaned and must be discarded when choked. The cos of replacement and compares more the Teele the lowest possible figure compatible with special care in manufacture: for any engine installing ennDl with ober ess eficient tering elements. The number of fies used wi Exam conditions of operation: tray obviously depend upon the capacity of the particular engine and the | Inall cases, ‘ y ane consistent with long filler element fie sets to provide the highest possible degree of iterator oie ; Doe to the Widely differing conditions of operstion wich kayo toe catceed Sx, pasioe sastaacioab Sox ted for paper elements ; and operators are advised to follow in the first down in the vehicle, tractor or engine instruction book. The period at to change the filter element will naturally vary according to the type of fuel m ly vary according to the type of fue use, provision made for bulk storage, setting or pre-filtering before filing the vehicle tank and the local conditions under which the engine concemed is working. This may easily be as short as three months or as long as twelve months, but it is not expected tha is peri i a at it will copmona pin Reema it will be outside this period although excep place the recommendations laid which it will be found necessary The filter inserts should never be cleaned. Every 5,000 km or 125 hours operation, the filter bowls should be drained to remove sediments/water. Since, filter inserts attain maximum efficiency only afier a film of dirt has deposited on the surface of the filter insert, the stage I and stage II filter inserts should never be replaced at the same time. Sometimes, the filter inserts get clogged in a very short time due to asphaltence or waxy compounds present in the fuel. In such cases, the filter insert has to be replaced, 15.7. FUEL FILTER INSERTS Developments over the years have led to the use of paper as the filteration ‘media. Paper is particularly suitable because the important properties which determine filter quality, such as pore size and pore distribution, can be maintained effectively during manufacture, Moreover, a paper filter has a large surface area giving correspondingly longer service life. However, for first stage filteration cloth pre-filter inserts are also used, Coil type paper filter insert. For coil type filter inserts, the : filter paper is wound round a tube and neighbouring layers (60pe2) inser. are glued together at the top and bottom as shown in Fig. ps cs sae! 15.12. This forms pockets with their openings at the top. The fuel flows along the V-form coil axially from the bottom to the top and the dirt particles which are held in the filter pockets. Star type paper filter insert. In star type filter inserts, the fuel flows radially from the outside to the inside. The paper folds are sealed at the top and at the bottom by end covers. The filtered fuel collects inside the perforated centre tube and flows upwards. The dirt particles are trapped on the filtering surface or settle down at the bottom. Principal of paper elements spiral construction. The paper element, wound round a circular core in the form of a spiral, is contained in a thick paper or a thin metal canister. The winding is done in such a manner as to provide a very large PERFORATED CENTRE TUBE RED OUTER BOARD ae cross EL oust eS re15-10 Automobile Engineer filter area within minimum filter bowl dimensions ; and actually gives six times the filter area of the norma) cloth filter within a bowl of approximately two-thirds the size. The method of construction and the direction of flow of the fuel oil are shown in Figs. 15.14 and 15.15. CLEAN FUEL = ——} \ FUEL LINE i) PAPER SPIRAL NY A | i A SEALING RING L\S= DIRTY FUEL, Fig. 15.14. Spiral construction, Fig. 15.15. Fuel flow through elements. _ Fig. 15.16. Cloth type inser Fig, 15.14 shows diagrammatically the way in which the paper spiralis constructed. Dirty oil is confined to the undersides of the paper coils and filtered oil to the upper sides. The large filtering surface will be apparent. Fig. 15.15 shows the path taken by the fuel in passing through the element. The actual number of tums of Paper is, of course, much greater than depicted in the diagram, the paper being wound closely but allowing continuous oil space between adjacent. Cloth type pre-filter insert. For first stage filteration, cloth type filter inserts are used. These filter inserts are also available in 0.5 and 1.1 litre. capacity. In cloth type filter inserts the fuel flows radially from outside. The cloth is coiled round a perforated tube and the ends sealed at the top and bottom by end covers. 15.8. FUEL INJECTION PUMPS In-line enclosed camshaft fuel injection pump. To deliver accurately measured amounts of fuel at high pressure to the injectors. The amount of fuel delivered should be controlled precisely with regard to the timing, rate and duration ; and must satisfy the work the engine is required to do. General design. All our in-line Fuel injection pumps are of cam-operated, spring return, plunger type, using one pumping unit for each engine cylinder ; and incorporates its own camshaft and tappet gear. Each pumping unit comprises the following essential components : 1. Pumping element (barrel and plunger) 2. Delivery valve and seating. Barrel and plunger, valve and seating are highly ground steel-being finished to finest limits and with the highest degree of precision to permit of accurate operation at high speeds and pressures : each pair must, therefore, be regarded as inseparable and not interchangeable, To enable the pump to vary the quantity of fuel delivered per stroke, the plunger is provided witha vertical channel extending from its top edge to an annular groove, the upper edge of which is cut inthe from of a helix. External means are provided whereby the plunger can be rotated in its barrel during operation. CO caves Hine