US3690768A

US3690768A - Diesel fuel injection system with improved starting performance

Info

Publication number: US3690768A
Application number: US882829A
Authority: US
Inventors: Shigeo Nagasawa
Original assignee: Mitsubishi Motors Corp
Current assignee: Mitsubishi Motors Corp
Priority date: 1969-02-28
Filing date: 1969-12-08
Publication date: 1972-09-12
Anticipated expiration: 1989-09-12
Also published as: DE2009365A1; FR2031090A5; GB1305087A

Abstract

A fuel injection system for a diesel engine has a plunger barrel with a fuel intake port and a plunger slidable axially in the barrel. A plunger operating cam has a pair of lobes for operating the plunger. During either the intake or the compression stroke, the cam advances the plunger to a first position blocking the port to inject fuel, after which the plunger retracts. At the end of the compression stroke, the cam advances the plunger further to a second position to block the port to inject fuel. A switching device is effective to rotate the plunger between a starting position and a running position. In the starting position, the peripheral surface of the plunger blocks the port during the two fuel injection strokes of the plunger and, in the running position, the plunger is rotated to a position where its peripheral surface blocks the port only upon the further advance of the plunger to the second position. The invention improvement comprises at least one fuel passage in the plunger connecting the peripheral surface to the inner end face of the plunger and communicating with a by-pass fuel intake port in the barrel, only during starting of the engine, and in the second plunger position. The by-pass fuel intake port is spaced angularly from the main fuel intake port.

Description

United States Patent Nagasawa [54] DIESEL FUEL INJECTION SYSTEM WITH'IMPROVED STARTING PERFORMANCE [72] Inventor: Shigeo Nagasawa, Kyoto, Japan [73] Assignee: Mitsubishi Jidosha Kogyo Kabushiki Kaisha, Tokyo, Japan 221 Filed: Dec.8, 1969 211 Appl.No.: 882,829

[30] Foreign Application Priority Data Feb. 28, 1969 Japan .,44/14560 [52] US. Cl ..l23/32 G, 123/l79 L, 123/32 R, 123/179 G [51] Int. Cl. ..F02b 3/00, F02n 17/00 [58] Field of Search ..l23/32.6l, 32.6, 179 L [56] References Cited UNITED STATES PATENTS 1,818,580 8/1931 Prestage "417/457 2,250,877 7/1941 Pischinger ..123/32.6l 2,306,364 12/1942 Skaredoff ..l23/32.61 2,713,310 7/1955 Muraszew ..123/32.61 2,871,796 2/1959 Dreisin et a1. ..12'3/32.6l 2,960,079 11/1960 Monnot et a1. ..123/32.6l

FOREIGN PATENTS OR APPLICATIONS 393,875 8/1922 Germany ..l23/32.61 607,230 12/1934 Germany ..l23/32.6l 851,570 10/1952 Germany; ..123/32.6l 360,980 4/1938 Italy ..l23/32.6l 465,887 9/1951 Italy ..123/32.61 514,011 10/1959 Great Britain [23/3261 [15] 3,690,768 1451 Sept. 12,1972

532,094 1/1941 Great Britain l 23/32.6l 610,095 10/1948 Great Britain ..l23/32.6l 688,003 2/1953 Great Britain ..l23/32.6l 893,621 4/1962 Great Britain ..l23/32.61 960,760 l/l944 France 1 23/3261 Primary Examiner-Laurence M. Goodridge Assistant Examiner-Ronald B. Cox Attorney-McGlew and Toren [5 7] ABSTRACT A fuel injection system for a diesel engine has a plunger barrel with a fuel intake port and a plunger slidable axially in the barrel. A plunger operating cam has a pair of lobes for operating the plunger. During either the intake or the compression stroke, the cam advances the plunger to a first position blocking the port to inject fuel, after which the plunger retracts. At the end of the compression stroke, the cam advances the plunger further to a second position to block the port to inject fuel. A switching device is effective to rotate the plunger between a starting position and a running position. In the starting position, the peripheral surface of the plunger blocks the port during the two fuel injection strokes of the plunger and, in the running position, the plunger is rotated to a position where its peripheral surface blocks the port only upon the further advance of the plunger to the second position. The invention improvement comprises at least one fuel passage in the plunger connect ing the peripheral surface to the inner en face of the plunger and communicating with a by-pass fuel intake port in the barrel, only during starting of the engine, and in the second plunger position. The by-pass fuel intake port is spaced angularly from the main fuel intake port.

1 Claim, l7v Drawing Figures Patented Sept. 12, 1972 4 Sheets-Sheet 1 a m N M m m N w o e m h S B 2 G F Patented Sept. 12, 1972 3,690,768

4 Sheets-Sheet 2 (Prior Ari) FIG. 4

Com lift 2 /First step upon running First step 3 --,--Second step upon stoning siorting\/ Com angle (9 22 Ho Starting Ho 22 j 1F llb r qrllo llo Running llb 22 Fl 6 (Prior Art) o r"x r-\ Anozzle needle volve lift IXVENTOR. Shigeo a 3a sawa Beginning of Compression top reol compress Crank angle 6.

Fl 7 (Prior Art) g ATTORNE YS Patented Sept. 12, 1972 3,690,768

4 Sheets-Sheet 5 Com lift {3 First step upon running Second step upon starting El First step Cum angle upon 22 23 stortmg 2L Z4a 22 t Ila f22- zg -24 24 2 '23 ll 2 j u u 22 724 ,24 22 Q 3 22b 3 I 1. f2 Uz 23 FIG 9A I Fl B INVESTOR.

' Shigeo Naqasawa A TTORHE Y5 Patented Sept. 12, 1972 4 Sheets-Sheet 4 FIG.|IB

FIG.I3A

FIG.I3B

DESEL FUEL INJECTION SYSTEM WITH IWROVED STARTING PERFORMANCE BACKGROUND OF THE INVENTION In a known conventional diesel engine, it has been common practice to start fuel injection several degrees before the upper dead point 3) in the compression stroke and either upon starting or during running.

Ifthe atmospheric temperature is low during starting, then, due to the fact that the entire engine is at a low temperature plus the fact that the'temperature of the intake air is low, the air in a cylinder chamber cannot obtain a sufficiently high temperature even though the air is compressed. Consequently, the ignition lag is extended and, during the injection period of several degrees before the upper dead point in the compression stroke, the time in which the fuel droplet makes contact with the high temperature air, within the compression chamber, is shortened. Thus, ignition of the fuel droplet becomes very difficult.

In another known type of diesel engine, prior to the fuel injection and several degrees before the upper dead point in the compression stroke, an auxiliary fuel injection is performed at the beginning of the compression stroke. In this type of diesel engine, the overall weight of injection of the fuel is substantially constant either upon starting or upon running. The object of this type of diesel engine is to enhance the efficiency of the engine by improving the combustion conditions of the fuel, and also to facilitate control of the operation.

While this type of diesel engine has excellent starting characteristics due to the two-stroke auxiliary fuel injection, it has a disadvantage. Since the second step of auxiliary fuel injection follows the first step and, since the amount of fuel injected in the first step is determined by a cam lift of a plunger, it is impossible conveniently to adjust the time of commencement of fuel infection in the second step without varying the quanti' ty of fuel injected in the first step, and without replacing a plunger operating cam by a cam having a different contour.

SUMMARY OF THE INVENTION This invention relates to fuel injection systems for diesel engines, and, more particularly, to an improved fuel injection system for a diesel engine greatly enhancing the starting performance under low temperature conditions.

The invention is directed to an improvement upon the type of diesel engine fuel injection system mentioned above and involving auxiliary injection of fuel during starting. In this type of fuel injection system, a plunger barrel has a fuel intake port and a plunger is slidable axially in the barrel. A cam operates the plunger and has cam lobes peripherally spaced in such a manner that, after the plunger has been advanced, during the intake stroke or the compression stroke, to a first position, and retracted, the plunger, at the end of the compression stroke, is advanced further to a second position. A switching device is operable to rotate the plunger through substantially 180 between a starting position and a running position.

ln the starting-position, the fuel intake port is blocked by the plunger peripheral surface so as to carry out two fuel injection strokes during the movement of the plunger to the first position and to the second position, respectively. In the running position, the plunger is rotated to a position in which the fuel intake port is blocked by the plunger peripheral surface, to effect fuel injection, only when the plunger is moved to the second position.

In accordance with the invention, a flow passage is provided in the plunger, connecting the peripheral surface of the plunger with its inner end face within the barrel, and a by-pass fuel intake port is provided in the barrel and spaced angularly form the main fuel intake port. In the starting position of the plunger, the flow passage communicates with the by-pass fuel intake port when the plunger is advanced to the mentioned second position. In the running condition of the engine, the plunger is rotated to a position in which the flow passage can no longer communicate with the by-pass fuel intake port.

The invention arrangement has the advantage that, even if the atmospheric temperature is too low for the intake air to obtain a sufficiently high temperature, by setting the switching device at the starting position, the fuel is mixed uniformly with the intake air for a long time and then heated up in the first step of auxiliary fuel injection, so that the ignition lag is reduced to an extent that ignition occurs with certainty. The torque necessary for rotating the engine can be produced in the second step of auxiliary fuel injection. Thereafter, during running of the engine while the temperature of the engine is increased, fuel injection is performed only upon movement of the plunger to the second position, by switching the control or switching device to the running position. Thus, the engine will run smoothly while the fuel is being injected exactly at the rate necessary for running. Furthermore, the rate of fuel injection, during running, may be substantially reduced with respect to the rate of fuel injection during the starting, thus preventing a reduction in thermal efficiency.

More particularly, the inner space of the barrel is connected to the by-pass fuel intake port, only in the starting position of the plunger, between the time the plunger attains its first position and the time the plunger attains its second position. Thus the time of commencement of fuel injection may be arbitrarily adjusted, as well as the quantity of injection in the second step, by appropriately delaying the time at which the by-pass fuel intake port is blocked by the plunger peripheral surface, and without changing the contour of the cam.

An object of the invention is to provide an improved fuel injection system for diesel engines.

Another object of the invention is to provide such a fuel injection system for diesel engines in which the starting operation is greatly improved.

A further object of the invention is to provide such an improved fuel injection system for diesel engines in which the rate of fuel injection, during running of the engine, may be substantially reduced with respect to the rate of fuel injection during starting of the engine, preventing any reduction in thermal efficiency.

Another object of the invention is to provide such a fuel injection system for diesel engines in which the time of commencement of fuel injection, as well as the amount of fuel injection in the second auxiliary injection step, may be arbitrarily adjusted without varying the contour of a plunger operating cam or without changing the plunger operating cam.

For an understanding of the principles of the invention, reference is made to the following description of typical embodiments thereof as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a somewhat schematic longitudinal cross section view of a prior art fuel injection system for a diesel engine;

FIG. 2 is a view similar to FIG. 1 but illustrating a different form of prior art fuel injection system;

FIG. 3 is a partial side elevational view taken along the line IIIIII of FIG. 2, looking in the direction of the arrow;

FIG. 4 is a longitudinal sectional view, to a larger scale, of a principal part of FIG. 2;

FIG. 5 is a schematic diagrammatic view of the fuel injection system shown in FIG. 2;

FIG. 6 is a graphical illustration of the relation between the cam lift and the plunger upon starting and running respectively, of the system shown in FIG. 2;

FIG. 7 is a graphical illustration of the operating principle of the fuel injection system shown in FIG. 2;

FIG. 8 is a schematic diagrammatic view of one embodiment of fuel injection system, for a diesel engine, in accordance with the invention;

FIG. 9A is a somewhat graphical illustration of the relation between the cam lift and the plunger, upon starting and running, respectively, of the embodiment of the invention shown in FIG. 8;

FIG. 93 illustrates, in correlation with FIG. 9A, the respective angular positions of the plunger during starting and during running;

FIG. 10 is a schematic sectional view of the principal part of another embodiment of the invention;

FIG. 11A is an axial sectional view illustrating a modified form of the invention;

FIG. 1 1B is a diarnetric sectional view corresponding to FIG. 1 1A;

FIGS. 12A and 13A are views, similar to FIG. 10, illustrating a further modification of the invention; and

FIGS. 12B and 13B are views, similar to FIG. 9B, but related to FIGS. 12A and 13A, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a known auxiliary chamber type of diesel engine, as illustrated in FIG. 1, when the air compressed in a main chamber b by an upward stroke of a piston a flows into an auxiliary chamber d through a communication part c, the air within chamber d is cooled due to the choke loss at low temperature of the port c. Thus, even at the end of the compression stroke, it is difficult for the air within auxiliary chamber d to reach the ignition temperature. Therefore, during starting, the fuel spray injected from a fuel injection pump e through a nozzle f into auxiliary chamber 11 must arrive in main chamber b by passing through auxiliary chamber d and port c. However, since the speed of the air current flowing from main chamber b through port c is rather high, it is nearly impossible for the fuel spray to arrive in main chamber b against this air current. Accordingly, the

starting performance is very poor, in an auxiliary chamber type of diesel engine, at low atmospheric temperatures.

To enhance the starting performance, there is a known fuel injection system for a diesel engine as illustrated in FIGS. 2 through 7. In this fuel injection system, a main chamber 1 has a piston 2 reciprocable therein, and main chamber 1 communicates with auxiliary chamber 4 through a port of aperture 3. In addition, a nozzle 6 provided with a nozzle needle valve 5 is mounted on auxiliary chamber 4, and a fuel injection pump body 8 is connected to nozzle 6 through tubing 7.

In fuel injection pump body 8, there is slidably fitted, for axial reciprocation, a plunger 12 provided with a notched step portion 11, plunger 12 being mounted beneath a delivery valve holder 10 having a delivery valve 9. Plunger 12 is arranged to be driven axially of body 8 by means of a cam 13 which is rotated in synchronism with the rotation of the diesel engine.

A rack 14 meshes with teeth (not shown) on the outer periphery of plunger 12, and rack 14 is coupled to one end 15b of a fork lever 15 which is pivotally supported approximately at its center portion 15a. The other end of fork lever 15 is in abutment with a sliding shaft 16a of an adjusting mechanism 16. An arm 15d extends from center portion 15a of fork lever 15, and is coupled to an adjustment knob or lever 18 through a spring 17. In addition, fuel injection pump body 8 is provided with a start button 19. 22 is a main fuel intake port provided on plunger barrel 8a within pump body 8.

In this fuel injection system, if adjustment knob or lever 18 is preset to a starting position as shown in FIG. 5, and if start button 19, shown by a broken line in FIG. 4, is moved to the solid line position of FIG. 4, a rack pin 20, projecting from rack 14, is released from a stop 21 for movement of the rack from the running position to the starting position. Thereby plunger 12 is rotated to a position where the upper portion 11a of the notched step portion of inner end face 11 of plunger 12 is opposite fuel intake port 22.

Under these conditions, if the engine is rotated by means of a known starter device, which has not been illustrated, cam 13 is rotated counter-clockwise as viewed in FIGS. 2 and 3. Plunger 12 is displaced by a first cam lobe 13a from a lift 1 shown in the left half portion of the upper section of FIG. 6, to another lift 1 shown in the right half portion of the upper section in FIG. 6. During this period of time, fuel intake port 22 is blocked by upper portion or projection 1 1a of the inner end face 11 of plunger 12. Thus, a first fuel injection step is carried out to inject substantially one-half of the total amount of fuel to be injected. The timing for raising plunger 12 by means of the first cam mold 13a is set at the end of the intake stroke or at the beginning of the compression stroke. Therefore, the fuel injected into auxiliary chamber 4 by the first fuel injection step flows into main chamber 1 through port or aperture 3. During the compression stroke, this fuel is sufficiently mixed with the intake air and is heated to a high temperature.

When first cam lobe 13a passes by the lower end of plunger 12, plunger 12 is lowered for a time to interrupt the fuel injection. Thereafter, a second cam lobe 13b comes into contact with the lower end of plunger 12 to raise plunger 12 and, upon arrival of the plunger at lift 1 a second step of the fuel injection is begun. Meanwhile, the temperature tm, shown in FIG. 7, of the mixture gas consisting of the mixed air and fuel within main chamber ll becomes higher than the temperature tp within auxiliary chamber 4. Thus, gas within main chamber I is more easily ignited than within auxiliary chamber 4. Furthermore, the fuel injected in the second step also flows, at least partially, into main chamber 1 in the period when the speed of the current through aperture 3 is reduced, the fuel flowing through aperture 3 burning with the mixture gas so that the explosion force necessary for starting may be obtained and thus the engine may be started very easily.

When the engine has obtained a predetermined rpm, sliding shaft 16a slides in the direction of the arrow in FIG. 5, under the influence of centrifugal force of a weight 16b of adjusting mechanism 16. Correspondingly, rack 14 is moved, through fork lever so that plunger 12 is turned through 180 and the lower portion 11b of the notched inner end face of plunger 12 is opposite fuel intake port 22.

Under these conditions, even if plunger 22 arrives at lift 1 due to first cam lobe 13a, fuel injection cannot be attained because fuel intake port 22 has not been blocked. It is only when plunger 12 arrives at lift 1 due to second cam lobe 13b, that fuel intake past 22 is blocked by the lower portion lllb of the notched inner end face 11 of plunger 12, to cause the fuel to be injected. Thus, fuel injection in a smaller quantity than during starting, and exactly similar to a conventional engine, is effected for enabling sustaining of a normal running operation.

In addition, even though the engine has not obtained a predetermined rpm, if adjustment knob or lever 18 is set at the running position, plunger 12 is turned and an adjustment is made so that lower portion 11b of inner end face I]. is opposed to fuel intake port 22.

In the known fuel injection system shown in FIGS. 2 through 7, by adjusting the height of the step portion of the inner end face ll of plunger 12, or the lift 1 and of the cam lobes, or both, in various manners, the amount of fuel injected in the first step during starting can be set at 25-75 percent of the total fuel injection amount, and the total fuel injection amount, during starting, can be set at 150-300 percent of the total fuel injection amount for the maximum output upon running.

As mentioned the known fuel injection system shown in FIGS. 2 through 7, has a better performance, during starting, than a direct injection type of engine, due to the fact that, upon starting, a first fuel injection step is effected at the beginning of the compression stroke when the speed of the air current in aperture 3 is low, so that the fuel can enter in sufficient amount into main chamber 1 whereby ignition may occur in chamber 1 at a higher temperature that the temperature tp of the compressed air in auxiliary chamber 4.

, However, since the second step of fuel injection is begun at the movement when plunger 12 rises again and has arrived at cam lift 1 after it had initially been lifted to the level I and then been retracted, and since the fuel injection amount in the first step is defined by the cam lifts l and 1 it is impossible conveniently to adjust the time of initiation of fuel injection in the second step without varying the fuel injection amount in the first step and without replacing cam 13 by another cam having a different contour.

Referring to FIGS. 8, 9A and 9B, in accordance with the present invention, a fuel injection system, such as shown in FIGS. 2 through 7 is modified by providing a by-pass fuel intake port 23 in barrel 8a at a position angularly displaced by in a horizontal plane, with respect to main fuel intake port 22. Particular reference is made to FIG. 9B, as the illustration in FIG. 9A represents a development rather than an actual section, in order to clarify the mutual relation between main fuel intake port 22 and by-pass fuel intake port 23.

In addition, plunger 12 is formed with a communication path or flow passage 24 in a manner such that bypass fuel intake port 23 in barrel 8a, and the inner space of barrel 8a inwardly of the inner face of plunger 12, communicate with each other when plunger 12 is disposed at cam lift 1 and has been rotated to its starting position. Thus, when plunger 12 is rotated to its starting position, so that the upper step portion 11a of notch step portion 11 is opposed to main fuel intake port 22, then, as illustrated in the upper half of FIG. 9, an opening 24a, on the peripheral surface of plunger 12 and corresponding to flow passage 24 is located in the same vertical or axial plane as by-pass fuel intake port 23. When plunger 12 reaches a position corresponding to cam lift 1 due to operation of the plunger by cam lobe 13a, the upper inner space within barrel 8a and by-pass fuel intake port 23 communicate with each other through flow passage 24.

Thus, even if plunger 12 is raised somewhat upwardly from cam lift 1 by the second cam projection 113b, the second step of fuel injection is not commenced until the opening 24a on the peripheral surface of plunger 12, and forming the termination of passage 24, has been displaced upwardly out of alignment with bypass fuel intake port 24 and up to the position of cam lift 1 At the position of the plunger corresponding to cam lift 1 communication between the upper space within barrel 8a and by-pass fuel intake port 24 is interrupted, and thus the second step of fuel injection is initiated.

However, as illustrated in the lower half of each of FIGS. 9A and 9B, when plunger 12 is turned through to be switched to the running state, as opening 24a of flow passage 24, located on the peripheral surface of plunger 12, is directed away from by-pass fuel intake port 23, and also directed at a right angle to main fuel intake port 22, there is no possibility for the upper space within barrel 8a to communicate with either main fuel intake port 22 or by-pass fuel intake port 23 until plunger 12 arrives at a position corresponding to cam lift 1 Thus, the time of initiation of fuel injection, as well as the amount of injection in the running condition, do not differ from those in the case where flow passage 24 is not provided, and therefore they are maintained constant.

In this embodiment of the invention, it is possible to adjust the time of initiation of fuel injection, as well as the amount of injection in the second step during starting, in a very simple and easy manner by varying the diameter, the height, or both of opening 240 on the peripheral surface, without modifying the shape of

cam lobes

13a and 13b. Thus, a fuel injection, upon starting, which is most suitable for the various characteristics of the engine, such as, for example, starting characteristics, output power, noise, etc., to enhance the performance of the engine, can be attained.

In an alternative embodiment of the invention, bypass fuel intake port 23 may be provided in barrel 8a at a position diametrically opposite to main fuel intake port 22, instead of a position at right angles to main fuel intake port 22, and on the same level as in the first mentioned embodiment. In this case, the schematic views in the left lower portion of FIG. 9A should be read as schematic longitudinal sectional views of the fuel injection pump rather than as developments, as mentioned previously. In accordance with this alternative embodiment, if plunger 12 is provided with flow passage 24 in such a manner that this flow passage connects the inner space of barrel 8a with by-pass port 23 at the posiu'on wherein plunger 12 is at the cam lift l and has been rotated to the starting position, then, when plunger 12 is turned by 180 to the running position, even though plunger 12 arrives at a position corresponding to cam lift 1 where the peripheral surface of the lower step portion 11b of plunger 12 blocks main fuel intake port 22, due to the fact that the inner space of barrel 8a and main fuel intake port 22 are connected with each other through flow passage 24, fuel injection is not initiated at cam lift 1 due to the presence of flow passage 24. This is in contrast to an arrangement wherein flow passage 24 is not provided, so that fuel injection is initiated at cam lift 1 It is only when opening 24a of flow passage 24 has passed upwardly across main fuel intake port 22, and thus communication between main fuel intake port 22 and the inner space of barrel 8a has been interrupted, that fuel injection for running is commenced or initiated with delay.

In this manner, according to the alternative embodiment of the invention, not only during starting but also the time for initiation of fuel injection as well as the amount of injection during running can be easily adjusted.

In the embodiment of the invention shown in FIGS. 8 and 9, a notched step portion 11 is provided. However, the same function and advantage can be obtained when the upper or inner end face of plunger 12 is cut obliquely as shown in FIG. 10, and flow passage 24 is formed so as to dispose opening 24a at the side toward the higher end of the obligque end face of plunger 12.

Alternatively, instead of providing different top levels of plunger 12 on the respective sides, by forming the top face of plunger 12 in a plane perpendicular to the axis of the plunger, while providing a plurality of fuel intake ports 22 on barrel 8a at different levels, fitting a sleeve around the outer periphery of barrel 8a so as to be freely displaced in the axial and circumferential directions, and selectively displacing an opening formed in the sleeve to a position opposed to one of the plurality of fuel intake ports 22, there can by achieved two step injection upon starting and one step injection during running. Furthermore, although a single flow passage 24 has been shown in the illustrated embodiments, if desired two or more flow passages may be lgg rovided.

GS. 11A and 11B illustrate the first-mentioned alternative embodiment, the parts being shown in the running stage of a two-stage fuel injection. A sleeve 151 with angularly spaced

radial ports

152a and 152b, and keyed to an operating member by virtue of a key 153, surrounds barrel 8a and is angularly displaceable. The sleeve is also formed with a by-pass 23b. In the position of the parts for running, port l52b communicates with port 22b of barrel 8a. In the starting position, port 152a communicates with port 22a of barrel 8a, radial passage 24a of plunger 12 communicates, through port 23a of barrel 8a with port 23b of sleeve 151, and port 22b is out of registry with port 152b.

The embodiment of the invention having two flow passages is illustrated in FIGS. 12A and 12B, wherein plunger 12 is formed with axially spaced

ports

24a and 24b communicating with port 24. The sleeve 151 is formed with a port 23. The parts are illustrated in the starting position.

FIGS. 13A and 13B illustrate the alternative embodiment involving three axially spaced

ports

24a, 24b, and 240 in barrel 12, and again the parts are illustrated in the starting position.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. In a fuel injection system for a diesel engine, of the type including a plunger barrel, having a radial fuel intake port, a plunger slidable axially in the barrel, a plunger operating cam having peripherally spaced lobes engageable with the plunger and operable, during one of the intake and compression strokes, to advance the plunger to a first position to block the port to inject a first quantity of fuel and then to provide for plunger retraction to free the port, the cam, at the end of the compression stroke, advancing the plunger further to a second position to block the port to inject a second quantity of the same fuel, and a switching device effective on the plunger, only during starting of the engine, to position the plunger angularly so that its peripheral surface blocks the port during advance of the plunger to the first and second positions, to effect two injections of the same fuel, and only during running of the engine, to position the plunger angularly so that its peripheral surface blocks the port, for single injection of the same fuel, only upon advance of the plunger to the second position: the improvement comprising a radial by-pass fuel intake port in said barrel in addition to said first-mentioned radial fuel intake port and at least one flow passage in said plunger connecting said peripheral surface of said plunger to the inner end face of said plunger and communicating with said by-pass fuel intake port, only during starting of the engine, in said second plunger position; there being a plurality of fuel intake ports in said barrel at different levels; and a sleeve enclosing said barrel and displaceable axially and circumferentially thereof; said sleeve having an opening therein cooperable with a selected one of said fuel intake ports.