After 40 thousand kilometers of the TOYOTA E (4Y - type), there is no medium and high speed after starting, and the carburetor backspray gasoline when the low speed is turned down; the exhaust sound is thick and easy to extinguish. When the cylinder head cover is disassembled, the swing of the valve rocker is very small, and the valve opening is seriously insufficient. The hydraulic tappet is removed and the tappet coupling is blocked and stuck. After cleaning, the fault is slightly improved. Finally, the oil pump was removed and the pump body and rotor shaft were broken, and the oil pump failed. The above fault occurs only if there is no engine oil into the valve hydraulic tappet, which makes the valve opening seriously inadequate. After replacing the oil pump, the trouble is eliminated and the engine work is restored to normal. Fortunately, after the failure of the engine oil pump, the engine only made short idle idle speed, and the crankshaft bearing and connecting rod were lubricated by a small amount of oil with splash, so no serious damage was caused.