Usage:
3116 (9GK) Truck Engines
Reference: Service Manual, SEBR0551, 3116 Diesel Truck Engine
The catalytic converter is a device located in the exhaust stream of an engine. The catalytic converter promotes chemical reaction to reduce air pollutants. Caterpillar has a combined (integral) catalytic converter/muffler package.
Some precautions should be noted for the operation of catalytic converter/mufflers. If a vehicle has operated for 72 or more consecutive hours without any operation under loaded conditions, the vehicle should be operated at rated conditions for 5 to 15 minutes. This should "clean out" the catalytic converter.
If the vehicle is not responding properly, see "Troubleshooting - Low Power", in the Reference. Proper driving techniques and maintenance are key factors in assuring full life of catalytic converter/mufflers. Be sure to follow the "Operating the Engine" and "Maintenance Schedule" section of the Operation And Maintenance Manual.
Periodic visual inspection of the converter/muffler is a good idea. Regular checks for indentations, damaged mounting hardware, and leaks can prevent faulty converter/muffler operation. See "Disassemble And Assemble - Converter/Muffler" in the Reference for replacement of catalytic converter/muffler components.
Problem 1. Loss of Engine Response/Power Loss
Vehicles equipped with catalytic converter/mufflers, especially those that idle for long periods of time and/or operate in cooler climates, are susceptible to plugging. One indication of a plugged converter/muffler is poor engine response. The following two methods may be necessary for checking/unplugging converter/mufflers.
NOTE: Method 2 should be performed after every 100 hours of continuous idling operation. This will help avoid plugging of converter/mufflers.
A. Install a back pressure tap on a straight length of exhaust pipe. This back pressure tap should be located as close as possible to the turbocharger or exhaust manifold (on a naturally aspirated engine), but the tap should be at least 305 mm (12 in) downstream of a bend. If an uninterrupted straight length of at least 457 mm (18 in) is not available [305 mm (12 in) preceding and 152 mm (6 in) following the tap], care should be taken to locate the tap as close as possible to the neutral axis of the exhaust gas flow. To make the pressure tap, weld or braze a 1/8inch NPT "half coupling" to the exhaust pipe at the desired location. Then drill a 3.18 mm (.125 in) diameter hole through the exhaust pipe wall inside the "half coupling". Remove any burrs from inside the exhaust pipe around the hole that was just drilled. The gauge or gauge hose can be attached to the "half coupling".
B. Attach a water manometer or back pressure gauge [range 0 to 2032 mm (0 to 80 in) of water recommended] in the previously installed back pressure tap.
C. Operate the vehicle at high idle for one to two minutes while continuously monitoring back pressure.
D. If the back pressure is greater than 1016 mm (40 in) of water, proceed to Method 2 that follows.
E. If the back pressure does not exceed 1016 mm (40 in) of water, refer to the Reference, "Troubleshooting: Low Power".
A. If possible, operate the vehicle under loaded conditions [exhaust temperature between 300 and 400°C (572 and 752°F) for 5 to 15 minutes]. This may "clean out" the converter.
B. If the high idle back pressure is not less than 1016 mm (40 in) of water, place the vehicle on a chassis dynamometer.
C. Operate the vehicle at rated conditions for 5 to 15 minutes while continuously monitoring back pressure. When the back pressure stabilizes, check high idle back pressure again.
D. If back pressure is not less than 1016 mm (40 in) of water, the converter/muffler should be replaced.
E. If back pressure is less than 1016 mm (40 in) of water, refer to the Reference, "Troubleshooting: Low Power".
Problem 2. Damaged Converter/Muffler
If a converter/muffler has been damaged due to a road hazard, shipping, installation, or other reason, Problem 1 (above) may be the result. Regular visual inspections should be performed.
Converter/muffler damage:
If a converter/muffler has been damaged and you are experiencing poor engine response and/or low power, replace the entire converter/muffler. Refer to the converter/muffler installation guidelines when replacing the unit.