To prevent early deterioration and breakage of an O-ring by a method wherein a high pressure and an impact pressure are prevented from being propagated directly to the O-ring to effect liquidtight sealing of a timer housing.

In the timer device of a distribution type fuel pump, O-ring grooves 64 and 65 separated. away from a cylinder bore 52 are formed in the end face of a timer housing 51. O-rings 66 and 67 are inserted in the O-ring grooves 64 and 65 and timer covers 55 and 56 are fixed to the end face of the timer housing 51. Thus, the O-rings 66 and 67 are separated away from a cylinder bore 52, and a fuel pressure in the cylinder bore 52 is not propagated to the O-rings 66 and 67.