Fuel Return Line Missing?

[miguel schindler]

This is my 68 IH 1200c 3/4 ton 2WD. 90k original miles. Ive had it about 6 months. At the top of the fuel pump in the photo I have circled a small tube with a flange on it where it appears that a hose should attach? Something is missing as it leaks fuel when the engine is running. Is it supposed to be a return line to the tank for the excess fuel in the pump? How do I fix this? I am handy but not awesome at fixing stuff on my own. I can follow instructions well. Thanks for any suggestions.

 

[FDChappie]

I think that tube is for a vacuum pump, which would not be needed for your truck. If it's leaking gas it is probably because the diaphragm is bad. I'd replace that pump asap because gas can get into the crankcase and dilute the oil.

 

[Robert Kenney]

That is to vent the back side of the pump diaphragm. Most simply had a vent in the casting. If there is fuel there it indicates the diaphragm has a hole in it and the pump is bad.
On a marine application, that would be plumbed to the carburetor air horn so it wouldn’t end up in the bilge and possibly cause a fuel fire or explosion. On the automotive application it can be vented out and down with a short hose.