[MMunger]

I recently acquired a restored 70 T/A. Working back through prior owners info, it seems it was done about 18 years ago and only had 550 miles on it since.
Since getting it about a month ago I have put on about 125 additional miles.
The issue is I have now ran it out of gas twice.

When the car arrived the gauge was very close to empty. I drove it to a close gas station and it only took about six gallons, and the gauge then showed full. From this my first thought was the in tank float was not accurate.

Since I knew the car was full I drove it a few times over the next week or so and it ran out of gas at about 60 miles. This time the gauge showed about 2/3 full.
Luckily I was right next to a gas station when it started to starve for fuel and I nursed it in. Again, it was full with a little over six gallons.

Over the next week or so I drove it a little, but didn't think that much. I took it to meet some buddies for dinner near my house, and again pulling into the parking lot it started to starve for fuel. I got it parked in the parking lot and had a buddy bring me five gallons to put in the car. It started right up and I drove it straight to a near by gas station. Again to fill it up, it only took about two additional gallons (again about 6-7 total) and the gauge shows full.

My first thought is the fuel pick up in the tank has a hole in it and it starts sucking air instead of fuel when the level in the tank gets below that.
This is my speculation, but not having an F-Body prior to this not sure if this is possible or may be something else.

Thoughts or input?

Mike

[GRNMTGOAT]

I wonder if you have a non vented gas cap, therefore pulling a vacuum till you remove the cap to refuel?

[MMunger]

Interesting thought. I just went out to the garage to check, and the cap doesn't say "vented" on it. Would the original cap have said "vented' on it?

[Formulabruce]

On a Norwood built and sold outside of CA, would gave a vented cap. Tiny, but vented. A vaccum could create this but you would hear a huge whoosh sound when you take off cap

[78w72]

are you filling it until the pump shuts off or just until the gauge says full? sounds like the sender is bad & not reading right.

if you fill until the tank is actually full & it dies after 60 miles or other low mile number there may be a problem with the pick up like you mentioned or something else. but if you fill just to the gauge reads full its the sender or gauge.

a 70 (non ca) should have a vented cap, it allows air in but will stop air/fuel going out. its a small hole but if working it will vent the tank. they sell new vented caps at auto parts stores.

[MMunger]

I am filling it up until the pump stops, which unfortunately is so full I have been getting some out of the neck, even when going really slow.

That's pretty much exactly what my cap looks like. Is there an easy way to tell if it is vented or not?

[78w72]

if you look at about the 5 oclock position on the pic i posted, you can see a small hole in the cap, that is the vent. hard to tell if your cap has that, if it doesnt its not a vented cap. on the inside it has the hole like yours.

you can test it by sucking in on the inside hole & it should flow air without too much suction, then blowing out it will stop air flow, kinda like a PCV valve or one way valve. yours looks pretty dirty so if it is a vented cap maybe its plugged up. the new caps are cheap.

[NOT A TA]

My first thought reading the OP was non vented cap got stuck on a '70 like others mentioned and that looks like it might not be a vented cap. So I'd try driving it and stopping to see if it sucks air when the cap is removed. Should have a cap like this

[MMunger]

So I looked closely at the cap again today and it does not have the vent like in 78w72's image.
Mine is definitely more like the pics NOT A TA posted, but does not say "Anti Surge - Vented"

I am starting to lean towards cap being incorrect. It is supposed to be nice out all next week so I'll drive it some and see if it sucks air when I remove the cap.

[necdb3]

If the tank is unvented, the tanks normally collapse from the tank going into a vacuum. Is the tank collapsed? Being that wasn't mentioned I doubt that's his problem. I would drop the tank and inspect the pick up and sending unit. It's likely has the wrong one being someone just restored the car.

[78w72]

try a new vented cap... vented caps will stop the tank from collapsing or building a vacuum creating the "sucking air" scenario. or go one step further & buy a tank vent with roll over protection, i got one for my unvented 70 tank from tanks inc & it works great, no pressure or vac in the tank.

https://www.firebirdcentral.com/1969..._p/fue-59r.htm

https://www.tanksinc.com/index.cfm/p...prod/prd98.htm

[Transamric]

I see that your valve in your cap is pretty crusty so that even if it is a vented design (and it appears it is), it may not be working properly. As others have said, just buy a modern aftermarket cap as a trial. If nothing changes with the problem, we'll go to the next test step.

[Transamric]

BTW, I'm not too many miles away from you. So perhaps an in person test session may prove helpful. (I'm a retired auto tech/shop owner).

[MMunger]

I'm revisiting this issue as I still have the issue after replacing the cap with a new vented one. Next step is to replace the fuel pick up.
I went onto Firebird Central to order one and they have listed one with a return line and one without.
I am out of town so can't get to the car to check but want to order the correct fuel pick up and sending unit.

Being a Norwood car I would think no return line but want to make sure to order the right one.

Is this the correct one? https://www.firebirdcentral.com/1970...8_p/fue-26.htm

[78w72]

Originally Posted by MMunger

I'm revisiting this issue as I still have the issue after replacing the cap with a new vented one. Next step is to replace the fuel pick up.
I went onto Firebird Central to order one and they have listed one with a return line and one without.
I am out of town so can't get to the car to check but want to order the correct fuel pick up and sending unit.

Being a Norwood car I would think no return line but want to make sure to order the right one.

Is this the correct one? https://www.firebirdcentral.com/1970...8_p/fue-26.htm

that looks like the right one for a non return set up. might want to consider getting one with a return, if your tank isnt vented thats an easy way to add a vent valve, or if you ever use a later vapor return factory pump that is where it can be connected.