Facts About Generators
GeneratorsDirectoryCompareRepairEnginesControllersPartsManufacturersGuides
Search models or part #
Home›Repair guides›Atomizes — Meters — Pressurizes):

Detroit Diesel 53 — Atomizes — Meters — Pressurizes):

For the Detroit Diesel 53.

Browse Detroit Diesel generators & specs →

Procedure

  1. Accurately times the moment of fuel injection.
  2. Atomizes the fuel for vaporization and mixing with the air in the combustion chamber.
  3. Meters and injects the correct amount of fuel required to maintain engine speed and to handle the load.
  4. Creates the high pressure required for proper fuel injection. FOLLOWER ~~ FOLLOWER SPRING + FILTER GEAR GEAR RETAINER UPPER tl ae : CONTROL PORT BUSHING RACK SPILL 159! DEFLECTOR NUT 598 VALVE SEAT INJECTOR VALVE VALVE stop CAGE Fig. 1 — Fuel Injector Assembly EFFECTIVE EFFECTIVE EFFECTIVE STROKE NO IDLING INJECTION tOaD LOAD 4209 LOAD Fig. 2 — Fuel Metering from No Load to Full Load Combustion required for satisfactory engine operation is obtained by injecting, under pressure, a small quantity of accurately timed, metered and fineiy atomized fuel oil into the combustion chamber. Metering and timing during fuel injection is accomplished by an upper and lower helix machined in the lower end of the injector plunger. (Fig. 2) illustrates the fuel metering from no load to full load by rotation of the plunger in the bushing. (Fig. 3) illustrates the phases of injector operation by the vertical travel of the injector plunger. The continuous fuel flow through the injector serves, in addition to preventing air pockets in the fuel system, as a coolant for those injector parts subjected to high combustion temperatures. To vary the power output of the engine, injectors having different fuel output capacities are used. The fuel output of the various injectors is governed by the effective stroke of the plunger and the flow rate of the spray tip. INJECTION STROKE STROKE INJECTION Fig. 3 ~ Phases of Injector Operation Through Vertical Travel of Plunger SEC. 2.1. Page 1 2.1 Fuel Injector DETROIT DIESEL 53 OUTLET IDENTIFICATION TAG Fig. 4 ~ Injector Identification Since the helix angle and the plunger design determines the operating characteristics of a particular injector, it is imperative that the specified injectors are used for each engine. If injectors of different types are mixed in an engine, erratic operation will result and may cause serious damage to the engine or to the equipment which it powers. Each fuel injector has a circular disc pressed into a recess at the front side of the injector body for identification purposes (Fig. 4). Each injector control rack (Fig. 1) is actuated by a lever on the injector control tube which, in turn, is connected to the governor by means of a fuel rod. These levers can be adjusted independently on the control tube, thus permitting a uniform setting or fine tuning of all of the injector racks. The injectors used in engines with a four valve cylinder head require an offset injector body due to the restricted area around the exhaust valve mechanism. A narrower injector clamp is required with the offset injector body and may not be used with the standard injectors. Most offset body injectors, designated as the “S” type, incorporate a clamp seat which is machined lower on the injector body and requires the current narrower clamp (Fig. 5). The fuel injector combines in a single unit alli of the parts necessary to provide complete and independent fuel injection at each cylinder. Page 2 INJECTOR WITH HIGH CLAMP (FORMER) SPRING 2 LOW | CLAMP STAMPED U INJECTOR WITH LOW CLAMP (CURRENT) W156 Fig. 5 - Comparison of High Clamp and Low Clamp Injectors Operation Fuel, under low pressure, enters the injector at the inlet side through a filter cap and filter positioned over the rack (Fig. 1). From the filter, the fuel passes through a drilled passage into the supply chamber, that area between the plunger bushing and the spill deflector, in addition to that area under the injector plunger within the bushing. The plunger operates up and down in the bushing, and is supplied fuel through the two funnel-shaped ports in the bushing wall. The motion of the injector rocker arm is transmitted to the plunger by the follower which bears against the follower spring (Fig. 6). In addition to the reciprocating motion, the plunger can be rotated around its axis by the gear which meshes with the control rack. To accomplish fuel metering an upper helix and a lower helix are machined in the lower part of the plunger. The helix relationship to the ports ---CHUNK BREAK--- changes with the rotation of the plunger. As the plunger moves downward, under pressure of the injector rocker arm, some of the fuel under the plunger moves into the supply chamber through the lower port until the port is covered by the lower end of the plunger. The fuel below the plunger continues to move up through the T-drilled passage in the plunger into the fuel metering recess and into the supply chamber through the upper port until that port is covered by the upper helix of the plunger. With the upper and lower ports both covered the remaining fuel trapped under the plunger is subjected to increased pressure by the continued downward movement of the plunger. : iS DETROIT DIESEL 53 Fuel Injector 2.1 Fig. 6 — Fuel Injector Mounting When sufficient pressure is built up, the injector valve is lifted off of its seat and the fuel is forced through small orifices in the spray tip and atomized into the combustion chamber until the lower port becomes uncovered. A check valve, mounted in the spray tip, prevents air in the combustion chamber from entering the fuel injector through the spray holes. At the end of the stroke the injector plunger is then returned to its original position by the injector follower spring. (Fig. 3) shows the various phases of injector operation by the vertical travel of the injector plunger. On the return stroke of the plunger, the bore of the bushing is again filled with fuel oil through the ports. The constant circulation of fresh cool fuel through the injector renews the fuel supply in the chamber, helps cool the injector and also effectively removes all traces of air which might otherwise accumulate in the system and interfere with accurate metering of the fuel. The fuel injector outlet opening, through which the excess fuel oil returns to the fuel return manifold and then back to the fuel tank, is directly adjacent to the inlet opening. Changing the position of the helices, by rotating the plunger, retards or advances the closing of the ports and the beginning and ending of the injection cycle. At the same time, it increases or decreases the amount of fuel injected into the cylinder. (Fig. 2) shows the various plunger positions from no load to full Joad. With the control rack pulled out all the way (no injection), the upper port is not covered by the helix until after the lower port is uncovered. Consequently, with the rack in this position, all of the fuel is forced back into the supply chamber and no injection of fuel takes place. With the control rack pushed all the way in (full injection), the upper port is covered shortly after the lower port has been covered, thus producing a maximum effective stroke and maximum injection. From this no injection position to full injection position (full rack movement), the contour of the upper helix advances the closing of the ports and the beginning of injection. General Instructions for Injector Care and Overhaul The fuel injector is one of the most important and precisely built parts of the engine. The injection of the correct amount of atomized fuel into the combustion chamber at exactly the right time depends upon this unit. Because the injector operates against the high compression pressure in the combustion chamber, efficient operation demands that the injector assembly is maintained in first-class condition at all times. Proper maintenance of the fuel system and the use of the recommended type fuel filters and clean water-free fuel are the keys to trouble-free operation of the injectors. Due to the close tolerances of various injector parts, extreme cleanliness and strict adherence to service instructions is required. Perform all injector repairs in a clean, well lighted room with a dust free atmosphere. An ideal injector room ts slightly pressurized by means of an electric fan which draws air into the room through a filter. This pressure prevents particles of dirt and dust from entering the room through the door and windows. A suitable air outlet will remove solvent fumes along with the outgoing air. Provide the injector repair room with a supply of filtered, moisture-proof compressed air for drying the injector parts after they have been cleaned. Use wash pans of rust-proof material and deep enough to permit all of the injector parts to be completely covered by the cleaning solvent when submerged in wire baskets of 16 mesh wire screen. Use baskets which will support the parts so as to avoid contact with the dirt which settles at the bottom of the pans. Rags should never be used for cleaning injector parts since lint or cther particles will clog parts of the injector when it is assembled. A lint-free paper tissue is a suitable material for wiping injector parts. When servicing an injector, follow the general instructions outlined below:
  5. Whenever the fuel pipes are removed from an injector, cover the filter caps with shipping caps to keep dirt out SEC. 2.1 Page 3 2.1 Fuel Injector DETROIT DIESEL 53 of the injector and prevent damage. Also, protect the fuel pipes and fuel connectors from damage and the entry of dirt or other foreign material. After an injector has been operated in an engine, do not remove the filter caps or filters while the injector is in the engine. Replace the filters only at the time of complete disassembly and overhaul of an injector. Whenever an injector has been removed and reinstalled or replaced in an engine, make the following adjustments as outlined in Section 14: a. Time the injector. b. Position the injector control rack. Whenever an engine is to be out of service for an extended period, purge the fuel system, then fill it with a good grade of rust preventive (refer to Section 15.3). When a reconditioned injector is to be placed in stock, fill it with injector test oil J 26400. Do not use fuel oil. Install shipping caps on both filter caps immediately after filling. Store the injector in an upright position to prevent test oil leakage. NOTICE: Make sure that new filters have been installed in a reconditioned injector which is to be placed in stock. This precaution will prevent dirt particles from entering the injector due to a possible reversal of fuel flow when installing the injector in an engine other than the original unit. e DDC recommends that flared end fuel pipes not be reused. Remove Injector 1. Clean and remove the valve rocker cover. Discard the gasket. Remove the fuel pipes from both the injector and the fuel connectors (Fig. 6). NOTICE: Immediately after removal of the fuel pipes from an injector, cover the filter caps with shipping caps to prevent damage and to prevent dirt from entering the injector. Also, protect the fuel pipes and fuel connectors from damage and the entry of dirt or foreign material. e DDC recommends that flared end fuel pipes not be reused. Crank the engine to bring the upper ends of the push rods of the injector and valve rocker arms in line horizontally. If a wrench is used on the cran

Source: manual:Detroit-Diesel-Series-53-Service-Manual-03.pdf. Figures and steps are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.