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Fuel Oil System

Fuel Pump Pump Barrel and Timing Guide

Each engine cylinder is equipped with its The pump barrel is guided at the top andown VIT (Variable Injection Timing) fuel bottom of the pump housing. Three low-fric-pump, which is mounted on the roller guide tion sealing rings are fitted in grooves in thehousing over the camshaft section corre- barrel to seal between barrel and housing.sponding to the cylinder concerned. The barrel is provided with a drain bore bet-

The square base of the fuel pump housing isprovided with a groove to receive any lea- The pump barrel has a threaded lower endking oil, which is subsequently drained off which fits into the internal threads of the ti-through a drain pipe. ming guide.

Two bores are provided in the base for toot- The timing guide has a gear rim to mesh withhed racks. The upper rack serves to adjust the upper toothed rack at the base of thethe injection timing via the timing guide, and pump housing. The gear rim and toothedthe lower rack controls the quantity of fuel oil rack are marked with lines enabling the partsdelivered by the pump via the regulating to be positioned correctly after disassembly.guide. The toothed rack is linked to a servo-air cy-

At the top, the pump housing is closed by a the regulating shaft. The position of the up-top cover, which incorporates a combined per toothed rack determines the vertical po-puncture valve and suction valve. The cover sition of the barrel relative to the plungeris attached by means of nuts and studs fitted through the threaded connection.in the pump housing. A sealing ring is fittedin the lower part of the top cover, to seal bet- In this manner the initial moment of fuel oilween barrel and top cover. injection into the cylinder can be adjusted by

Oil is supplied through a flanged connectionon the front of the pump housing. A corre- The pump barrel is prevented from turningsponding flange on the back of the housing by means of a guide screw mounted on theis fitted with a shock absorber which neu- front of the pump housing.tralizes the shock caused when the plungeruncovers the cut-off holes at the end of eachdelivery stroke. Pump Plunger and Regulating Guide

The shock absorber consists of a cylinder The pump plunger is fitted within the barrelwith a spring-loaded plunger which is and ground accurately to form an oil-tightpressed back when the surplus oil from the seal. Barrel and plunger must always godelivery chamber is forced out into the inlet together and cannot be replaced individually.space round the pump barrel.

Two plug screws are fitted in the pump hou- in the barrel are covered and uncovered.sing opposite the cut-off holes of the barrel. This function, in conjunction with the turningThe oil jets which are ejected through the of the plunger effected by the regulatingcut-off holes at the end of the delivery stro- gear, serves to regulate the amount of oilke, hit the plug screws, which can be repla- injected into the engine cylinder.ced when they are eroded.

A guide pin fitted at the top of the pumphousing ensures correct positioning of theparts.

ween the two sealing rings in the lower end.

linder which is controlled by the position of

a servo-air cylinder.

During the travel of the plunger, cut-off holes

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The pump plunger is provided with a guide Fuel Oil Injectionblock designed to travel in the milled keywayin the regulating guide. At the bottom it has a During the suction stroke the spring-loadedfoot which rests on a thrust disc in the bayo- suction valve opens and the deliverynet joint at the roller guide neck. A clearance chamber is filled with oil.of approx. 0.1 mm between the plunger footand the roller guide permits the plunger to As soon as the plunger has covered theturn in the roller guide. cut-off holes in the pump barrel during its

The regulating guide has a gear rim which through the fuel valves. The vertical positionengages with the lower toothed rack at the of the cut-off holes thus controls the injectionbase of the pump housing. The gear rim and timing. Injection will last until the cut-off ho-toothed rack are marked with lines enabling les are uncovered by the oblique cut-off ed-the parts to be positioned correctly after ges, following which the oil is forced throughdisassembly. The toothed rack is linked to- two milled grooves at the side of the plungergether with the regulating gear of the engine and out through the cut-off holes of the bar-through a spring-loaded connection. Thus, in rel during the rest of the delivery stroke.the event of a sticking pump plunger, theregulating gear for the remaining fuel pumpswill not be blocked. Fuel Pump Actuating Gear

Puncture Valve pump, the exhaust valve actuating gear and

A puncture valve is fitted in the top cover of the cylinder frame.the pump. The puncture valve consists of apiston which communicates with the control On reversible engines, the roller guide forair system of the engine. In the event of ac- each fuel pump incorporates an angularlytuation of the shut-down system, or the "Fuel displaceable reversing link.Oil Leakage Alarm System", (option) or whenSTOP is activated, compressed air is supplied The fuel pump is actuated by a cam on theto the top of the piston, causing the piston to camshaft. The movement is transmittedbe pressed downwards and `puncture' the oil through the roller guide to the plunger in theflow to the fuel valve. As long as the punc- barrel of the pump housing which > throughture valve is activated, the fuel oil is returned the high-pressure pipes > is connected withthrough bores to the pump housing, and no the fuel valves on the cylinder cover.injection takes place.

Fuel Oil System roller guide and the pump base, so that the

The fuel oil is supplied through a pipe on the the camshaft. The pump base is attached tofront of the pump housing from the electrical- the camshaft housing by four studs. ly driven circulating pump. The oil pressureis kept constant by means of the overflow The thread on two of these is long enough tovalve, Plate 90915, which is located between permit the gradual easing of the roller guidethe main fuel oil supply line to the pumps spring when dismantling the components.and the return line. The fuel pump and the The plunger rests on a thrust piece in thefuel valves are designed for circulation of neck of the roller guide and is locked to thewarm oil, enabling them to be preheated roller guide by a bayonet lock. The roller gui-during standstill and in between the fuel oil de itself is prevented from turning injections.

upward movement, injection commences

A roller guide housing containing the fuel

the indicator drive, is bolted on to the side of

The roller guide is forced downwards by theaction of a helical spring fixed between the

roller of the roller guide follows the cam on

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by means of a guide block mounted in the Alternative 1:liner of the housing. Each fuel pump is, via drain pipes, connec-

The top of the roller guide neck is located corporates a level switch. The drain tank isinside the pump base and is equipped with a also equipped with an overflow pipe, whichcap. This cap, together with a sealing bush has a small drain bore below, whereby oilthat is shrunk into the pump base, form a from small leakages can be drained to thelabyrinth to prevent fuel oil from entering the outlet, without actuating the level switch.camshaft lube oil.

Each roller guide housing is provided with a ages in the system, the aforementioned borelifting device which can lift the fuel pump rol- will not be large enough to allow the increa-ler guide roller free of the fuel cam. The lif- sed oil quantity to pass, and the oil level inting device is mounted on the side of the rol- the drain tank will rise until it reaches theler guide housing. level of the overflow pipe. The rising oil level

For operation of the lifting device, see the alarm.instruction book, Volume II, Procedure 909-5.

The drain pipes of each fuel pump are con-Reversing mechanism (only reversible engines)

Reversing is achieved by shifting the roller inthe fuel pump drive mechanism at each cy- taining cylinder.linder. The link connecting the roller guideand roller is provided with a reversing arm, Alternative 3:and a pivot is mounted at the top end of the The drain pipes of each fuel pump are con-reversing arm. The pivot travels in a rever- nected to a diaphragm valve, which sets offsing guide connected to an air cylinder. The an alarm and activates the automatic liftinglink is self-locking in either the AHEAD or arrangement for the fuel roller guide, in orderASTERN position without the aid of external to stop the fuel oil flow from the pertainingforces. Each cylinder is reversed individually, pump.and the reversing mechanism is activated bycompressed air.

Fuel Oil High-Pressure Pipes Plate 90910

Plate 90913 The fuel valve consists of a valve head 173,

All high-pressure pipes in the system are within the valve body are non-return valveprovided with flexible, steelwire-armoured 207 with a combined slide/valve, thrusthoses or a protective outer pipe. The space spindle 220 with thrust spring 244, thrustbetween the pipe and the protective hose foot 256, and spindle guide complete 041. communicates, through drilled passages inthe flanges, with a drain bore in the pump When the fuel valve is fitted in the cylindertop cover. cover, the valve parts are tightened together

Fuel Oil Leakage Alarm (Option) thrust spindle and spindle guide complete to(Required for Unattended Machinery the valve body, which is pressed into theSpaces, UMS) tapered bore in the cylinder cover. The union

ted to a common drain tank, which in-

In the event of pipe fractures or major leak-

will cause the level switch to actuate an

Alternative 2:

nected to a diaphragm valve, which sets offalarm and activates the puncture valve inorder to stop the fuel oil flow from the per-

Fuel Valve

union nut 124 and valve body 100. Fitted

by the pressure from the nuts being transmit-ted through valve head, non-return valve,

nut keeps valve

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head and valve body together during dis- closed spindle of the non-return valve willmantling of the fuel valve. prevent the circulating pump from pressing

The spindle guide complete 041 consists of risk of the engine cylinder being filled withspindle guide 053, nozzle 077, thrust piece oil.016 and cut-off shaft 028. The spindle guideis assembled with a press fit.

Cut-off shaft 028 is pressed against the ta-pered valve seat of spindle guide 053 by the stroke, the pressure has risen to about 10action of the thrust spring 244, the spring bar, the force of the spring of the non-returnpressure being transmitted through the slot- valve will be overcome and the spindleted thrust foot 256. The thrust spring deter- pressed back against the shoulder of themines the opening pressure of the valve. thrust piece.

Optionally, an extra disc can be inserted to Position III:raise the opening pressure by 25 bar.

The non-return valve 207 consists of hous-ing, thrust piece, slide and spring. The non-return valve is assembled with a press fit.

The slide of the non-return valve is pressedby the spring against the tapered valve seatinside the non-return valve. In this positionthe head of the slide uncovers a small borearranged for circulation purposes in thethrust piece.

The functioning of the fuel valveis as follows:

Position I:The electrical fuel oil circulating pump circu-lates preheated oil through the fuel pumpand fuel valve. In the fuel valve the oil pas-ses through the central bore of the valve he-ad and continues to the thrust piece in thenon-return valve, leaving through the circula-tion bore of the latter. Thence the oil is pas-sed through the interior of the valve body toan outlet pipe on the side of the valve head.

The space round the tapered valve seat ofthe spindle of the non-return valve is alsofilled with oil, but the circulating pumppressure is insufficient to overcome the forceof the spring and the lift spindle.

If, for some reason, cut-off shaft 028 shouldnot close during engine standstill, then the

oil through the nozzle, and thus obviate the

Position II:When, at the beginning of the delivery

When the spindle of the non-return valve ispressed upwards, the circulation bore of thethrust piece is closed, and the oil passes theseat of the spindle and enters the spaceround cut-off shaft 028 in the spindle guide.When the pressure has risen to the presetopening value of the fuel valve, the spindle islifted, and oil is forced through the nozzleinto the engine cylinder.

At the termination of the delivery stroke, firstcut-off shaft 028 and then the spindle of thenon-return valve will be pressed against theirrespective seats, the injection of fuel stops,and oil is again circulated through the valve(position I).