3114, 3116 and 3126 Engines Caterpillar

This procedure assists in identifying a cylinder that has either of the following problems:

• Misfiring

• Engine knock

1. Proceed to Step 2 if an infrared thermometer or an exhaust temperature pyrometer is not available. Start the following procedure with a cold engine. Take all measurements within the first five minutes of operation. The temperatures of the exhaust manifold ports should be within 20 °C (68 °F). Low exhaust temperature can indicate that a cylinder is receiving less than the correct amount of fuel which can cause misfiring. High exhaust temperature can indicate that a cylinder is receiving more than the correct amount of fuel which can cause engine knock.

   1. Start the engine and operate the engine at low idle.

   2. Measure the temperature at the center of the number one exhaust manifold port and at the center of the number six exhaust manifold port. Compare the two temperatures.

   3. Measure the temperature of the number two exhaust manifold port and the number five exhaust manifold port. Compare the two temperatures.

   4. Measure the temperature of the number three exhaust manifold port and the number four exhaust manifold port. Compare the two temperatures.

2. Start the engine. Allow the engine to operate until the normal operating temperature is reached or until a misfire is detected.

3. Stop the engine and remove the valve cover.

4. Start the engine and operate the engine at low idle.

Show/hide table



Illustration 1	g00598910
(1) Fuel injection rack (2) Fuel-on direction

5. Use a screwdriver to move each fuel injection rack (1) to the fuel-on position. If an injector is delivering less than the correct amount of fuel, the cylinder will misfire. Moving the fuel injection rack to the fuel-on position will lessen the misfire. This may also eliminate the misfire. If an injector is delivering more than the correct amount of fuel, moving the fuel injection rack to the fuel-on position will increase an existing engine knock. Stop this test if the misfire or the engine knock can not be attributed to a specific cylinder.

6. If a misfire or engine knock can be isolated to a single cylinder, check the injection timing and the synchronization of the suspect cylinder. Make adjustments, if necessary. If adjustment does not resolve the problem, replace the injector. Ream the injector sleeve if the seat area for the injector is pitted. Replace the injector sleeve, if necessary. Refer to Troubleshooting, "Unit Injector". Verify synchronization and timing after replacing an injector.