gas tank sucking air in through the pop down cap

[jerry S]

I drove about 45 mins yesterday and when I went to open the trunk, I could hear air getting sucked into the tank. I opened the cap (flip down type) and heard a giant "whoosh!" and the tank made a popping sound, like when you inflate a collapsed plastic coke bottle. That is not good. I suggests to me that the tank was collapsing under vacuum. Is there supposed to be a vent from the tank to the air cleaner? Where should those fittings go on the tank? I got a replacement gas tank when the old one was found to be full of rust. Any suggestions how to fix this?

 

[robbz28]

If i'm not mistaken the gas cap should be vented somehow...My 69 camaro I had used to do that exact same thing, I went to autozone and got a new cap and it never did it again.

 

[pabear89]

Repo flip down covers are not vented and are for show only as stated on the box.
I drilled a 1/16 hole in the caps center for venting, and it does not spill out.
Only other way is to have a vented cap under the flip down cover.

 

[jcode68]

My buddies 67 had the same problem with the tank only better. He had just got the car and didn't know about this problem, he would drive maybe 15 minutes and the car would stall because the pump was starved for gas. Took days to figure out what was going on as it wasn't obvious. He drilled the smallest hole he could and never had a problem again.

 

[jerry S]

a 2mm hole has been drilled and I will see how it goes on Saturday.

 

[dodgestang]

Don't be suprised if you need a new sending unit after this little issue.

 

[other_shoe]

Don't be suprised if you need a new sending unit after this little issue.

Is there a reliable sending unit on the market these days?

My repro has never been close to accurate (e.g. full tank shows as 3/4) , and I got the impression this was a common problem.

 

[horseballz]

Nick,
That's quite a stable that you display.
Gene

 

[jerry S]

the 2mm hole fixed the problem.

As for the sending unit, I know that autometer sells a fuel sender that works with its gauges. I installed autometers on my car and decided to give a repop a try before getting this one and so far, the repop has been holding up perfectly.