My fuel sender failed on my 64.5 Mustang, and I noticed that the tank had been replaced with a newer unit (a tank with a drain) by the prior owner. Not sure why, but that gas gauge didn't work despite indicating that it should, so it was time to replace the sender.

When I looked under the car, I noticed that the sender in my car had TWO outlets, one for a tank vent, and one connecting to the gas line. I found out that this 2-outlet unit was designed for cars with fuel injection; mine is a 260 V-8 w/a 2-bbl carb. Therefore, I think that it was installed by the prior by mistake.

My question: if I replaced this defective fuel sender with the original configuration (standard) unit, that being a one-outlet fuel sender, how does the gas tank vent? I see no provision for a vent, and I do not understand how it does. Lack of a vent will collapse the tank, right?

Would someone explain how the tank venting works before I collapse my tank?

Thanks,
=rdsieber

 

On the filler neck there are two key slots that align with the cap. On a factory filler neck, the smaller of the two key slots has a small groove that allows the tank to vent.

 

@Mustang 66:
Thanks for your reply. I attached some photos of what I have, since I couldn't identify what you describe.

 

Yep, right there ->

 

I would pull the tank and replace it with a 22 gallon version that was used in the 1970 Mustang. Use the 1970 sender and one of the modified filler necks meant to adapt the 22 gallon tank to the earlier mustangs. All the screws/bolts line up properly with no issues. I believe both National Parts Depot and CJ Pony can supply everything needed.