COVER AS-VALVE 2696348 - Caterpillar

All Truck EnginesThis article gives the procedures used at Caterpillar to make engine fuel settings and the procedure that must be used in the field. It also tells why there can be differences between the fuel setting dimension on the fuel setting microfiche, the dimension on the engine information plate and the actual setting.
Before a new engine arrangement is built, design specifications and engine tests are used to find the correct fuel setting for that engine rating. Over a period of time as engines are built, components will change a small amount. Because of these changes the fuel setting specification must be changed to keep the average engine power as close as possible to the rating. The new fuel setting specification is then stamped on the engine information plate. The fuel setting microfiche has fuel setting dimensions for all the engines, but the dimension on the microfiche may not be exactly the same as the one on the engine information plate. The microfiche is changed only when the specification has changed more than 0.25 mm (.010 ") from what the setting was before. The dimensions in the microfiche can be used for engines which are to be set for a rating which is different from the rating set at the factory.
The dimension on the engine information plate is the most accurate and must be used as long as the engine is still in its original factory configuration.A new fuel setting "checking" tolerance must now be used on all engines. The new "checking" tolerances is 0.25 mm (.010") is only for when a fuel setting is checked. If the fuel setting is within the "checking" tolerance it must not be changed. The " checking" tolerance is not to be used to adjust the fuel setting. If the fuel setting dimension is outside the tolerance, it must be set to the dimensions on the engine information plate. 0.13 mm (.005 ") of the "checking" tolerance is necessary because it is possible for different servicemen with different sets of tools, to get different results. The other 0.13 mm (.005 ") is because of tolerances and changes at the factory.
When an engine is tested on a dynamometer and has correct Brake Specific Fuel Consumption (BSFC), it is permissible to adjust to a setting that is 0.25 mm (.010") different than the dimension specified on the engine information plate to get correct fuel rate and 3% of the rated power. However, if the setting from the dynamometer test is not within 0.25 mm (.010") of the information plate setting, it is recommended that the engine be thoroughly checked to make sure assembly or adjustment is correct. Remember, when a recheck of this by a different serviceman is made, the dimension can be as much as 0.28 mm (.015 ") different from the dimension on the plate.