Oval valve seal is the most common failure. This is due to the valve cone and valve seat cone surface with a tight cone is not due to scratches and other reasons. Fault performance and plunger wear similar. Can use the same method to check. In dismantling the fuel injection pump. If the past occasionally found no abnormalities, should check the sealing of the oil valve parts. First check the couple's two collars with pressure relief ring cylinder and valve cone surface, the method of checking the cone surface is mouth mouth suck parts seat mouth. With the tip of the tongue against the mouth, try to catch the tongue. If you can suck, indicating normal cone seal; if unable to absorb, then the cone is not sealed, it should be re-grinding. Dilute chromium oxide abrasive paste with oil and apply a small amount on the cone of the valve plug with the valve plug facing downwards. Gently grind until resumed seal. It is noteworthy that Do not make grinding green into the cylinder, so as to avoid the loose surface of the syphilis decompression zone. Check the decompression ring cylinder method is to use the left forefinger aldehyde oil to block the seat under the mouth of the couple, pinch the spool with the right hand to mention, in the wear belt is pulled out of the seat hole, if you can feel finger suction, Then decompression with a cylindrical surface with a good, if you can not feel the finger suction, then decompression ring cylinder with poor, should be replaced even parts.