Troubleshooting for insufficient engine power of Caterpillar CAT3512

A Caterpillar CAT3512 engine has insufficient power, which is manifested as: normal operation in neutral gear; When operating in II and III gears, the throttle automatically returns to 1150-1250r/min(the working range should be 1500-1800r/min), the pump pressure is 25Mpa, and black smoke is emitted. White smoke is emitted at low idle speed and when the machine stops. The fuel return pipe is overheated and the fuel consumption is excessive.

The possible causes of the malfunction may be poor fuel quality, low fuel pressure, incorrect valve clearance, a certain cylinder of the engine not working, wrong fuel injection timing, incorrect fuel quantity setting value, air leakage in the intake system, problems with the brake and its control lever, and carbon deposits in the turbocharger.

Eliminate the problem step by step from simple to complex: First, check if the fuel quality is qualified. Use fuel of qualified quality. Check whether each cylinder of the engine is working properly. After inspection, all cylinders are working normally. Check whether the fuel pressure is too low, whether the return fuel volume is too large, and whether the pressure of the return fuel valve is sufficient. Therefore, check the return fuel valve. Check the valve clearance and adjust the intake and exhaust valve clearances according to the allowable range of the valve clearance for the CAT3512 engine. Then, adjust the fuel injection timing and fuel quantity according to the instructions for setting the fuel injection timing and fuel quantity of this machine.

After completing the above checks and conducting a test run, it was found that when operating in I-III gears, the smoke exhaust was normal, but the rotational speed and pump pressure were both low. When operating in III gear, the brake does not move. After manually operating the throttle to control the connecting rod to accelerate, both the engine speed and the pump pressure of the large pump increased, but there was a phenomenon of black smoke. This might be caused by uneven acceleration when manually operating the throttle to control the connecting rod to accelerate.

Check the brake again at that time. First, check the circuit part of the brake, and the result is normal. When the brake was disassembled, dirt was found accumulated inside. Inspect and clean all components, install the brakes that have been inspected, and test the machine again. It was found that the fault phenomenon was somewhat alleviated.

Install a new brake and test the engine to observe the working conditions of each gear. The engine speed, pump pressure and exhaust are all normal.