1980/11/24 Caterpillar

Kysor Air-Operated Shutdown Actuators For 3406, 3408, 1693 Truck Engines


Some customers have Kysor air-operated shutdown actuators installed on Caterpillar 3406, 3408, and 1693 Truck Engines. With these installations, service personnel will possibly find it necessary to make adjustments or do troubleshooting work on these units. For assistance with possible problems, the information that follows is taken from a Kysor service bulletin. This service bulletin gives information about model applications, troubleshooting, and adjustment specifications for the Kysor air-operated shutdown actuators used on Caterpillar 3406, 3408, and 1693 Truck Engines.

Model Applications

The chart that follows shows the Kysor identification numbers of the different actuators according to engine model applications, and Kysor service part numbers for the main components of the actuators.


The paragraphs that follow are a list of possible problems and causes, with points to be checked and methods to use.

1. Engine stops or will not start.
A. Broken wire to solenoid valve, or loose wire connections.
B. Open coil (broken wire or connection) in solenoid valve. To check, use an ohmmeter to measure coil resistance. The correct coil resistance for a 12 Volt system is 15-21 Ohms, or 67-83 Ohms for a 24 Volt system.
2. Engine will not stop when the switch is turned off.
A. Inlet to solenoid valve closed by dirt or other foreign material.
B. Wrong actuator.
C. Wrong adjustment of actuator. See the topic "Adjustment Specifications".
3. Loss of power. Check the governor and fuel injection pumps according to information in the service manual.
A. Wrong actuator.
B. Wrong adjustment of actuator. See the topic "Adjustment Specifications ".
C. Solenoid valve leakage. To check: Remove the valve and connect it to air pressure and electrical sources as shown in Illustration 1 . Be sure the electrical source is the correct voltage, and the air pressure is not more than 825 kPa (120 psi). Connect the negative ( -) or ground wire of the electrical source to the brass body of the valve, and the positive (+) wire to the screw terminal on the valve. Put a drop of oil in the outlet port (opening) of the valve (the end with male threads) and look for bubbles in the oil. Bubbles are an indication of valve leakage, and a new valve must be installed.

NOTE: During assembly, an application of "Loctite" was used on the threads of the solenoid valve elbow. Use a small amount of heat to loosen the threads.

D. If the reason for loss of power is not found during the above checks and tests, it will be necessary to inspect the engine and fuel injection system for possible problems.

Illustration 1. Connections to check solenoid valve for leakage.

Adjustment Specifications

The correct adjustment specifications are shown in Illustrations 2 and 3. The Illustration Reference Chart shows which illustration to use for specific actuators and/or engine models.

To check the actuator adjustment, use the procedure that follows:

1. Remove the actuator, and remove the gasket from the mounting surface of the actuator. As shown in the illustrations, the adjustment is measured from the surface under the gasket, so the gasket must be removed for accuracy of measurement.

2. Measure the dimensions as shown, first with the plunger extended, then with the plunger retracted.

3. If the measured dimensions are not to the specifications shown, adjustment is necessary. To adjust, loosen the locknut on the plunger and turn the head on the rod. Tighten the locknut to a torque of 6.78-7.91N ·m. (60-70 lb in).

NOTE: During assembly, an application of "Loctite" was used on the threads of the plunger locknut. Use a small amount of heat to loosen the threads.

On plungers that have a locknut with a counterbore, check to be sure the locknut is installed with the counterbore toward the air cylinder.

Illustration 2. Adjustment specifications. See the Illustration Reference Chart for applications.

Illustration 3. Adjustment specifications. See the Illustration Reference Chart for applications.

Caterpillar Information System:

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