1970 Gas Tank Collapse

[Mark P.]

My 1970 L46 gas tank was rusty and so I replaced it about 18 months ago with the correct Quanta unit. I was advised to use a sealed gas cap and it has worked just fine until I took a recent trip. I noticed that the fuel gauge was not working properly and when I got home, I noticed that the fuel filler door had popped open. When I looked, the tank had risen up to pop it open and after opneing the gas cap, the inside of the tank had collapsed in on itself.

Could something have happened to the vent line? I can't imagine that it would create that much vacuum to collapse the tank if the line just got crimped. Why would this take that long to occur unless something seriously went wrong? Should I have just replaced the tank and utilized a vented cap and thus avoided the chance of possible collapse?

I would appreciate any and all responses with advice.

Thanks,
Mark

[Kenneth B.]

Re: 1970 Gas Tank Collapse

My 1970 L46 gas tank was rusty and so I replaced it about 18 months ago with the correct Quanta unit. I was advised to use a sealed gas cap and it has worked just fine until I took a recent trip. I noticed that the fuel gauge was not working properly and when I got home, I noticed that the fuel filler door had popped open. When I looked, the tank had risen up to pop it open and after opneing the gas cap, the inside of the tank had collapsed in on itself.

Could something have happened to the vent line? I can't imagine that it would create that much vacuum to collapse the tank if the line just got crimped. Why would this take that long to occur unless something seriously went wrong? Should I have just replaced the tank and utilized a vented cap and thus avoided the chance of possible collapse?

I would appreciate any and all responses with advice.

Thanks,
Mark

CALL QUANTA. BAD TANK or You must have a super fuel pump?
KEN

SEE SIMILAR THREADS

[Mike G.]

Re: 1970 Gas Tank Collapse

the reason it only showed up now is because the tank is nearly air tight not completely air tight. when you drive a short time and park it the tank over time leaks the vacume out. when you drive far and alot of fuel is displaced the vacume builds. i have heard of this happening before. the vent line runs along side the fuel line to the fuel pump. if that line is blocked it will create enough vacume to do that. its not a problem with the tank. if you get a new one it will do the same thing if the problem is not fixed. a vented cap will prevent this but its not a real fix.

[Kenneth B.]

Re: 1970 Gas Tank Collapse

the reason it only showed up now is because the tank is nearly air tight not completely air tight. when you drive a short time and park it the tank over time leaks the vacume out. when you drive far and alot of fuel is displaced the vacume builds. i have heard of this happening before. the vent line runs along side the fuel line to the fuel pump. if that line is blocked it will create enough vacume to do that. its not a problem with the tank. if you get a new one it will do the same thing if the problem is not fixed. a vented cap will prevent this but its not a real fix.

I agree. that's why I said to read the old posts below.
KEN

[Mark P.]

Re: 1970 Gas Tank Collapse

Are you saying that it is definitely a tank problem with the vent? Or could it be an issue with the vent return line?

Mark

[Joe L.]

Re: 1970 Gas Tank Collapse

All late 1969 and 1970-74 Corvette fuel tanks (+ all GM SERVICE fuel tanks for 1963-74 Corvette applications sold after 1970 until they were discontinued about 2 years ago) included an integral pressure-vacuum valve. The Quanta reproductions of the L69-74 tanks also includes the valve. If the valve is working properly, it does not matter what cap you put on the tank (but, like Quanta, I recommend the sealed cap). I would say almost certainly that the pressure vacuum valve on your tank was defective.

[Joe L.]

Re: 1970 Gas Tank Collapse

Are you saying that it is definitely a tank problem with the vent? Or could it be an issue with the vent return line?

Mark

Mark-----


If the integral pressure/vacuum valve is working properly, it does not matter what the situation is with the return line or lines.

[Mark P.]

Re: 1970 Gas Tank Collapse

Well, I called Quanta today and they take no responsibility. They say it's my fault or my venting system is faulty. Sounds to me like they don't stand behind their product. I could have sworn that the tank had a vent system in it, but I guess their vent system can't be trusted for anything and they don't guarantee it. Sounds like a heck of a way to do business to me. I even threatened to send them the tank so they could look at it, but they said no way...they don't want it. Shoot, I would have drained the gas out! Too bad I can't get one from somebody else because I am no longer a satisfied customer. They didn't even offer to help...just passed the blame.

Now that I got that out of the way, how do I diagnose what's wrong and should I do it with that tank still on the car? Also, anybody know any higher-ups in Quanta that I can complain to? Any help would be very much appreciated.

Thanks,
Mark

[Tom L.]

Re: 1970 Gas Tank Collapse

I don't think your going to find much in the way of "higher ups". I've been there a few times and it looks like a pretty small outfit. I've never seen more than two employees there. They don't manufacture the tanks. I think they're made in Canada.

[Joe L.]

Re: 1970 Gas Tank Collapse

Well, I called Quanta today and they take no responsibility. They say it's my fault or my venting system is faulty. Sounds to me like they don't stand behind their product. I could have sworn that the tank had a vent system in it, but I guess their vent system can't be trusted for anything and they don't guarantee it. Sounds like a heck of a way to do business to me. I even threatened to send them the tank so they could look at it, but they said no way...they don't want it. Shoot, I would have drained the gas out! Too bad I can't get one from somebody else because I am no longer a satisfied customer. They didn't even offer to help...just passed the blame.

Now that I got that out of the way, how do I diagnose what's wrong and should I do it with that tank still on the car? Also, anybody know any higher-ups in Quanta that I can complain to? Any help would be very much appreciated.

Thanks,
Mark

Mark-----


I just do not understand how a tank could collapse from excessive vacuum if the integral pressure/vacuum valve is working properly. The ONLY "venting system" on such a tank is the integral pressure/vacuum valve. There is no other "venting system" that is external to the tank and which, presumably, would be your responsibility, which could have caused the problem.

The removal of fuel from the tank by the fuel pump will create a vacuum. That vacuum has to be relieved by the integral pressure/vacuum valve since all 1970-74 Corvettes used a sealed fuel cap.

The integral pressure/vacuum valve does not relieve to ambient; it has pressure and vacuum set-points. However, it should NEVER allow vacuum in the tank to get to the point of collapsing the tank. If it did, why even have the valve?

[Joe L.]

Re: 1970 Gas Tank Collapse

Mark-----


One more thing I thought of: are you sure that the tank that you got from Quanta had the integral pressure/vacuum valve installed? It's presence can easily be confirmed by looking at the top of the tank, about 6 or 8 inches to the driver side of the filler opening. If it's there, it will be seen as a small, round, more-or-less flat device soldered into the tank. If there is no integral pressure/vacuum valve and you used a sealed type cap, then it's no wonder that your tank collapsed.

However, if the valve is present AND ASSUMING ITS OPERATING AS DESIGNED, you should not expect the tank to collapse regardless of what type of gas cap you had on it and regardless of any other connections to the tank. ALL 1970 tanks should have the pressure/vacuum valve. If yours does not, then it's not a 1970 tank. Period.

[Ken A.]

Re: 1970 Gas Tank Collapse

Quanta does not make the tank, it is made in Canada by a tank /fuel sender company. Sounds like they've cut some corners on steel thickness due to the rise in prices. Use a vented cap on the next tank is my advice.

[Joe L.]

Re: 1970 Gas Tank Collapse

Quanta does not make the tank, it is made in Canada by a tank /fuel sender company. Sounds like they've cut some corners on steel thickness due to the rise in prices. Use a vented cap on the next tank is my advice.

Ken-----


Yes, Quanta is not an actual manufacturer of fuel tanks. I believe these tanks are manufactured by Superior Industries which is a Canadian-based firm.

If the tank has an integral pressure-vacuum valve which is functioning properly, it should not be necessary or, even, advisable to use a vented type cap. The pressure vacuum valve should assume all of the functions of the vented cap. While it's possible that there has been a reduction in tank material thickness, I really doubt it. Too many product liability issues for that sort of change. Plus, even if the tank were thinner, it should not collapse if the pressure-vacuum valve is operating properly.

[Harmon C.]

Re: 1970 Gas Tank Collapse

Mark
If you can live without the logo that is not seen. Auto City Classics sells tanks made in Canada that look about the same and save you a few bucks.

[Tom L.]

Joe, is this it?

I just happen to have a new Quanta tank for a 1970 sitting in the garage waiting to be installed. It has something next to the filler opening. I assume that this is the valve. I can reach into the tank, this part is about 3/4" deep into the tank. My original tank has the same part in the same place.