PURPOSE: To prevent contamination of oil filler port as well as to improve the extent of appearance quality by forming a part of an engine hood with a door member capable of covering the oil filler port, and opening or closing the door member in use of a feeler jutting out of the back of this door member and a plate spring being engaged thereto.

CONSTITUTION: A part of a side wall rear end in an engine hood 16 is pivotally attached to a car body 10 independently, forming it into a door member, free of opening or closing, capable of covering an oil filler port 12. When the door member 20 is closed, the oil filler port 12 is covered, and sealed by a sealing member 32, while energizing force of a plate spring 30 via a feeler 22b of a first hinge 22 is made to act as moment in the normally closed direction. On the other hand, the door member 20 is pulled, the door member 20 is lightly opened by elastic deformation in the plate spring 30 with rotation of the feeler 22b and resilient energization after going beyond a dead center. In addition, the rotation of the feeler 22b is regulated by a bending part 30a of the plate spring 30, thus the door member 20 is kept in a specified opening position.