86 Honda accord, gasoline carb, auto

I bought this old 86 Honda accord car about six months ago and have
fallen in love with it.

My problem: about a month ago, it began running out of gas after using
only seven of the maximum ten gallons, now it only takes seven gallons
to fill it back up. Each time I remove the cap cap off the gas tank,
I hear a big rush of air, so I thought vacuum may be the problem, put
the gas cap back on, and drove another mile and out of gas. Still only
holds seven gallons.

Any thoughts or opinions would be very welcome,
thank you all
regards
david

 

Your fuel pickup in the tank may have a hole rusted into the side of
it as a result of water condensation in the tank.

 

Are you literally running out of gas, or do you mean that the gauge
shows empty?

Do you have the original gas cap?

As gas is pumped out of the tank, obviously air needs to enter the tank.
In the good old days, on some cars the air vent was a check valve in the
gas cap. Not sure if they still did this in 86. Every so often people
would replace the OEM gas cap with one that didn't have the vent, and
the result was that the gas tank would collapse as gas was pumped out of
it. I would think that a clogged EVAP system on newer cars could cause
the same problem. I would get under the car and check if the gas tank
looks OK.

 

Have you actually looked at the tank to make sure there isn't a big dent
in the bottom?
If no dent, then the fuel pick up tune isn't reaching all the way down for
some reason.