Engine start throttle buzzer

Valve response is usually caused by the failure of valve hydraulic ejector rod.

Working principle of valve hydraulic tappet: The work of hydraulic tappet mainly depends on the oil pressure, the clearance between tappet and seat hole, the clearance between valve stem and tappet and the check ball valve in tappet. When the hydraulic tappet works, under the action of oil pressure, the plunger cavity in the tappet is filled with oil, and the plunger moves downward, which increases the effective working length of the tappet and reduces the valve clearance. Because the force generated by the plunger in the tappet is too small to compress the valve spring, the tappet will not move when the clearance between the tappet and the valve is too small. At the same time, due to the function of the check ball valve in the tappet, the oil pressure in the plunger cavity of the tappet can not be discharged quickly, so that the plunger stays in its original position and maintains its original length to form rigidity, thus pushing the valve to open.

At the beginning of the vehicle, because there is no oil pressure in the cavity, the tappet plunger is at the bottom, and the gap between the tappet and the valve is large, resulting in short-term abnormal sound of the valve. With the operation of the engine, the tappet plunger is adjusted normally and the noise is eliminated.

However, if the hydraulic tappet wears for a long time, or the clearance between the valve stem and tappet and the balance of the check ball valve in the tappet change, it cannot be adjusted normally, and the clearance between the tappet cylinder and the seat hole and the clearance between the valve stem and tappet become larger, there will be noise. Elimination method-replace the valve hydraulic tappet!