Usage:
3500 Series Engines
The complete procedure to check and adjust the fuel injector timing is given in the Testing and Adjusting sections of the following Service Manuals for 3500 Series Engines: Pages 59, 60 of Form SENR2374 for 3500 Series Marine Engines, Pages 75, 76 of Form SENR2352 for 3500 Series Industrial Engines, Pages 59, 60 of Form SENR2362 for 3500 Series Generator Set Engines, and Pages 3-24, 3-25 of Form SEBR0548 for Vehicular Engines. Additional information is given in this article to make sure that the dial indicator readings are interpreted correctly by the service technician.
Dimension (A), shown in the illustration, is the actual fuel timing dimension of the unit injector. It is the distance from the top surface of the injector follower to the injector body. The body is used as a reference surface for measurement. If this dimension is not within the specifications given in the Fuel Setting and Related Information microfiche, the injection timing will be either advanced or retarded.
The specifications for the fuel timing dimension are not the same for all 3500 Series Engines. For example, Dimension (A) is 87.00 ± .20 mm (3.425 ± .008") on a correctly timed injector used in a current production high speed engine (1301 to 1800 rpm). On a low speed engine (900 to 1300 rpm) Dimension (A) is 87.64 ± .20 mm (3.450 ± .008"). The above dimensions are used here as examples only and may not be correct for future production engines. The correct fuel timing dimension for the engine that is being inspected must be obtained from the Fuel Setting and Related Information microfiche before any adjustment is made to Dimension (A).
Find the correct fuel timing dimension from the Fuel Setting and Related Information microfiche. Use the chart below to find the dial indicator setting that corresponds to the specified timing dimension. Use the 6V3117 Set Gauge to set the dial indicator to the desired reading.
After the dial indicator has been correctly set, place the indicator with the attached timing fixture on the injector follower surface. The roller on the lifter assembly must be on the base circle of the cam lobe and not on any other portion of the cam lobe. The correct position of the lifter assembly roller is shown in the illustration. Refer to the appropriate Service Manual for the procedure to correctly position the cam follower.
If the injector is correctly timed, the dial indicator will show a reading of 0.00 ± .20 mm. If the dial indicator gives a reading of + .21 mm or greater, this means the stem of the indicator has moved toward the dial indicator and Dimension (A) is shorter than it should be. Since the injector plunger is directly connected to the injector follower, a reading of + .21 mm means the injector plunger has moved too far down the injector barrel toward the combustion chamber. Timing will be too far advanced in this case.
If the dial reading is - .21 mm or less, Dimension (A) is longer than it should be. Negative numbers become less in value as they get larger (farther away from zero). Thus - .22 is less than - .21, - .23 is less than - .22, and so forth. The plunger is too far up the injector barrel and away from the combustion chamber. Timing will be too far retarded in this case.
To correct these last two conditions it will be necessary to loosen the locknut on the adjustment screw and turn the adjustment screw until 0.00 mm is indicated on the dial face. Tighten the locknut to a torque of 70 ± 15 N·m (50 ± 11 lb ft) and check Dimension (A) again.
Service Reporting
If the timing dimension needs to be measured and recorded for service reports before any changes are made to the dimension, proceed as follows:
1. Use the 6V3117 Set Gauge and the correct dimensions from the chart to set the dial indicator to the desired setting as previously described. Remember, if the dial indicator has been correctly set up off-engine in this manner, the indicator reading on-engine will always be 0.00 ± .20 mm on a correctly timed injector.
2. Compute the actual timing dimension (Dimension A) as measured on-engine. To do this, the dial indicator reading must be either added to or subtracted from the specified fuel timing dimension. Subtract the dial indicator reading from the specified dimension if the indicator reading is a positive number. Add the reading to the specified dimension if the reading is negative.
EXAMPLE 1. The specified timing dimension is 87.64 mm. The on-engine dial indicator reading is +0.27 mm. In this case the actual timing dimension is .27 mm subtracted from 87.64 mm. This equals 87.37 mm. Injector timing is too far advanced.
EXAMPLE 2. The specified timing dimension is 87.00 mm. The on-engine dial indicator reading is -0.49 mm. In this case, the actual timing dimension is the sum of 0.49 and 87.00 mm. (Ignore the negative sign when the negative dial indicator reading is added to the specified timing dimension.) This equals 87.49. Injector timing is too far retarded.
3. Record the data on the service report.
Dimension (A) is the fuel timing dimension.