The nozzle-and-holder assembly consists of the nozzle and the holder. The holder includes all of the required filters, springs and connec- tions.
The nozzle affects the diesel engine’s output, fuel economy, exhaust-gas composition and operating refinement. This is why the nozzle test is so important.
An important tool for assessing nozzle performance is the nozzle tester.
Nozzle tester
The nozzle tester is basically a manually oper- ated fuel-injection pump (Fig. 1). For testing, a high-pressure delivery line (4) is used to connect the nozzle-and-holder assembly (3) to the tester. The calibrating oil is contained in a tank (5). The required pressure is gener- ated using the hand lever (8). The pressure gage (6) indicates the pressure of the cali- brating oil; a valve (7) can be used to discon- nect it from the high-pressure circuit for specific test procedures.
The EPS100 (0684200704) nozzle tester is specified for testing nozzles of Sizes P, R, S and T. It conforms to the standards defined in ISO 8984. The prescribed calibrating oil is defined in ISO standard 4113. A calibration case containing all the components is required to calibrate inspect the nozzle tester.
This equipment provides the basic condi- tions for reproducible, mutually compatible test results.
Test methods
Ultrasonic cleaning is recommended for the complete nozzle-and-holder assemblies once they have been removed from the engine. Cleaning is mandatory on nozzles when they are submitted for warranty claims.
Important: Nozzles are high-precision com- ponents. Careful attention to cleanliness is vital for ensuring correct operation.
The next step is to inspect the assembly to determine whether any parts of the nozzle or holder show signs of mechanical or thermal wear. If signs or wear are present, it will be necessary to replace the nozzle or nozzle-and- holder assembly.
The assessment of the nozzle’s condition pro- ceeds in four test steps, with some variation depending on whether the nozzles are pintle or hole-type units.
Chatter test
The chatter test provides information on the smoothness of action of the needle. During injection, the needle oscillates back and forth to generate a typical chatter. This motion en- sures efficient dispersion of the fuel particles. The pressure gage should be disconnected for this test (close valve).
Pintle nozzle
The lever on the nozzle tester is operated at a rate of one to two strokes per second. The pres- sure of the calibrating oil rises, ultimately climbing beyond the nozzle’s opening pres- sure. During the subsequent discharge, the nozzle should produce an audible chatter; if it fails to do so, it should be replaced.
140 Service technology Nozzle tests
Fig. 1
1 Suction equipment 2 Injection jet 3 Nozzle-and-holder
assembly
4 High-pressure test line 5 Calibrating oil tank
with filter 6 Pressure gage 7 Valve 8 Hand lever Keep your hands away from the nozzle jet. Spray from the nozzle stings and penetrates the skin.
There is a risk of blood poisoning.
Wear safety goggles.
3
1 2 4 5 6 7 8
Nozzle tester with nozzle-and-holder assembly
1
æ
UWT00
7
When installing a new nozzle in its holder, always observe the official torque specifica- tions, even on hole-type nozzles.
Hole-type nozzle
The hand lever is pumped at high speed. This produces a hum or whistling sound, depending on the nozzle type. No chatter will be present in some ranges. Evaluation of chatter is difficult with hole-type nozzles. This is why the chatter test is no longer as- signed any particular significance as an as- sessment tool for hole-type nozzles.
Spray pattern test
High pressures are generated during this test. Always wear safety goggles.
The hand lever is subjected to slow and even pressure to produce a consistent discharge plume. The spray pattern can now be evalu- ated. It provides information on the condition of the injection orifices. The prescribed re- sponse to an unsatisfactory spray pattern is to replace the nozzle or nozzle-and-holder assembly.
The pressure gage should also be switched off for this test.
Pintle nozzle
The spray should emerge from the entire periphery of the injection orifice as even tapered plume. There should be no concen- tration on one side (except with flatted pin- tle nozzles).
Hole-type nozzle
An even tapered plume should emerge from each injection orifice. The number of indi- vidual plumes should correspond to the number of orifices in the nozzle.
Checking the opening pressure
Once the line pressure rises above the opening pressure, the valve needle lifts from its seat to expose the injection orifice(s). The speci- fied opening pressure is vital for correct op- eration of the overall fuel-injection system.
The pressure gage must be switched back on for this test (valve open).
Pintle nozzle and hole-type nozzle with single-spring nozzle holder
The operator slowly presses the lever down- ward, continuing until the gage needle indi- cates the highest available pressure. At this point, the valve opens and the nozzle starts to discharge fuel. Pressure specifications can be found in the “nozzles and nozzle-holder components” catalog.
Opening pressures can be corrected by re- placing the adjustment shim installed against the compression spring in the nozzle holder. This entails extracting the nozzle from the nozzle holder. If the opening pressure is too low, a thicker shim should be installed; the response to excessive opening pressures is to install a thinner shim.
Hole-type nozzle with two-spring nozzle holder This test method can only be used to deter- mine the initial opening pressure on two- spring nozzle-and-holder assemblies.
The is no provision for shim replacement on some nozzle-and-holder assemblies. The only available response with these units is to replace the entire assembly.
Leak test
The pressure is set to 20 bar above the open- ing pressure. After 10 seconds, formation of a droplet at the injection orifice is acceptable, provided that the droplet does not fall.
The prescribed response to an unsuccessful leak test is to replace the nozzle or nozzle-and- holder assembly.
Technical Terms
A
Absolute manifold-pressure compensator, 92
Actuator mechanism, electric, 100 Adjustments, 136
Altitude-pressure compensator, 91
B
Blind-hole nozzle, 113
C
Calibration devices, mechanical, 84 Cam shapes, 25
Cavitation, 127
Characteristic data of fuel-injection systems (overview), 5
Checking start of delivery, 138 Closed-loop control, 40 Combination governors, 54 Constant-pressure valve, 27 Constant-volume valve, 26 Control-lever stops, 84 Control-rack travel sensors
(Semi-differential short- circuiting ring) p Sensor Control-rod stops, 85 Control-sleeve actuator mechanism, 101 Control-sleeve in-line fuel-injection pump, 6, 104 Crossflow scavenging, 28 D Delivery valve, 26 Dimensions of diesel fuel-injection technology, 109 E Effective stroke, 22
Electric actuator mechanism, 100 Electric shutoff valve, 12 Electrohydraulic shutoff device, 13 Electronic Diesel Control EDC, 48 –, overview, 128
Electronic flow
measurement system, 135 Electronic idle-speed
control system, 93
Electronic Service Information, 133
F
Flatted-pintle nozzle, 111 Flow measurement methods, 134 Fuel delivery actuator mechanism, 107 Fuel filter, 11
Fuel lines, 10 Fuel preheating, 11 Fuel supply system, 10 Fuel tank, 10
Fuel-delivery control, 23-39
Fuel-injection pump test benches, 134 Full load, 42
G
Generator governor, 55 Glass gauge method, 134 Governor, 40 –, design, 56 –, functions, 44 –, overview, 52 –, type designations, 52 –, types, 47
Governors and control systems for in-line fuel-injection pumps, 53 Gravity-feed fuel-tank system, 17
H
Heavy-duty insert fittings, 124 High-precision technology, 117 High-pressure connection fittings, 124 High-pressure fuel lines, 125 History of the governor, 41 Hole-type nozzles, 112
I
Idle, 42
Idle-speed regulation, 45 In-line fuel-injection pump, 18 –, adjustment, 136
–, areas of application, 6 –, control, 7
–, design and method of operation, 19 –, EDC overview, 128
–, fitting and drive system, 19 –, for alternative fuels, 38 –, history, 25
–, operation (venting, lubrication), 39 –, shutting down, 39 –, size A, 31 –, size CW, 36 –, size M, 30 – size MW, 32 –, size P, 33 –, size P10, 34 –, size P9, 35 –, size ZW and ZWM, 35 –, system overview, 6 –, testing, 136-139 –, types, 6, 28 Intermediate-speed regulation function, 45 L
Leakage return channel, 24 Longitudinal scavenging, 28
M
Main filter, 11
Manifold-pressure compensator, 89 Manual priming pump, 11, 17 Maximum speed control function, 45 Maximum-speed governor, 52 Measured variables on diesel engines, 103 Minimum/maximum-speed governor, 52 Multifuel operation, 38 N
Needle-motion sensor p Sensor No load, 42
Non steady-state operation, 43 Nozzle cones, 114
Nozzle holders, 118
–, type designation codes, 118 –, without fuel leakage
connection, 119 Nozzle tests, 140-141 Nozzle-and-holder assembly, 118 Nozzle-needle damper, 121 Nozzles, 108 O Open-loop control, 40 Organic fuels, 38 Overflow valve, 12 Overrunning, 43 P Part load, 43
Perpendicular connection fittings, 125 Pintle nozzles, 110
Pneumatic governors, 40 Pneumatic idle-speed increase, 92 Pneumatic shutoff device, 97 Position control loop, 107 Preliminary filter, 11, 17 Preliminary phase, 22 Press pumps, 37 Pressure-relief phase, 22 Prestressed high-pressure delivery lines, 126 Presupply pump, 14 Proportional response of the governor, 43
Pulse-width modulation signal, 100 Pump plunger, 24
Pump-and-barrel assembly, 20 142 Index of technical terms