94 Explorer engine part identification

[Rhaegal94]

I am troubleshooting some starting issues and while checking vacuum lines/hoses, I came across this opening on the left side of the engine towards the back of the engine bay. Does anyone know what it is for? Should it be connected to something or have a cap on it? If a cap, any idea what size? I don't think I have noticed it before. I have a '94 Ford Explorer XLT.

 

[J_C]

Looks like a fuel rail valve. Yes a cap would help keep gunk out. See if a tire stem cap will fit. If not, an auto parts store will probably carry the right size.

 

[BKennedy]

It's a Schrader valve to test the fuel pressure. A tire stem cap should fit.

 

[Rhaegal94]

@J_C and and @BKennedy , thank you for your replies and help.