GOVERNOR AND FUEL INJECTION PUMP 6N0253 - Caterpillar

* As a replacement for 5L5644, 5L5645 install solenoid without modification. Extra plunger (1) is not needed. * As a replacement for 3L6657, 3L6672 install plunger (1) in place of plunger (2). The information that follows is for use on those solenoids that have an adjustable shaft that connects to the plunger.
The solenoid has two windings that are known as "pull in" and "hold". When the solenoid is activated, the plunger must be permitted to bottom (make its complete stroke). If it does not bottom, the result can be permanent damage within a very short time. A wrong adjustment of the solenoid plunger shaft is the cause of this type of damage.
* Adjust the length of the solenoid plunger shaft according to the dimensions given in the Service Manual Specifications. In the test that follows, when the solenoid is initially (first) activated, a high current reading will be seen on the ammeter for approximately 1/10 second, then the low current reading will be seen if the solenoid is adjusted correctly. * Install solenoid (3) on the governor. Connect a power source (4) (either 12 volt or 24 volt, according to the voltage of the solenoid) and an ammeter (5) to the solenoid as shown. Activate solenoid (3), check the current draw on ammeter (5), and check for the following conditions.1 - If the reading on the ammeter is the same as that shown in column (A) and the engine will shut down (stop), solenoid adjustment is correct.2 - If the reading on the ammeter is the same as that shown in column (A), but the engine does not shut down, adjust the shaft of the solenoid so it is shorter, until the engine does shut down, and the reading on the ammeter is the same as that shown in column (A), after the solenoid is activated.3 - If the ammeter reading is the same as that shown in column (B), adjust the solenoid shaft so it is longer, until the engine does shut down, and the reading on the ammeter is the same as that shown in column (A), after the solenoid is activated.