The Dodge Challenger Message Board

Does anyone know what is inside these tanks? It sounds like there is a valve inside mine when you shake it from side to side. I have been cleaning up some small parts with EvapoRust and have also been soaking this tank.

I blew compressed air into the tank through one of the four tubes on the back side. Very little air blew out the tube that leads to the charcole canister. I also have a pinhole leak in the tank and I need to know if it is worth saving or if I need to get a new one. Thanks

Hey Burdar - i know a bit about these bastards. I have one on my 73 and i took it off at first and just plugged up the 4 take off vents from the tank. Big mistake. I had all sorts of problems with what i thought was my new TQuad, but it was actually becasue the tank was pressurising! The fuel cap provided such a good seal ( it had no pressure relief like the factory ones) that the rising pressure in side the tank was pushing fuel through the lines and over riding the floats in the carb. I knew there was heaps of pressure (i guessed at least 5-7psi) because there was a huge whoosh of gas whenever i undid the fuel cap. So i had to put this vapour cannister back on. However that didn't solve the problem becasue not only did i not have a charcoal cannister (evaporative purge gas collection), but the evaporative fuel gas line was blocked with rust. So in the end, i connected it all up but had to use a temporary plastic fuel cap with a vent hole in it.

But back to the evap cannister. That rattle you hear is a one way valve. It stops fuel going through it when you over fill the tank. But the design allows gas fumes from the tank into the cannister to be collected/stored and shunted off to the charcoal cannister which is then purged everytime the engine starts. If you want you car original with the Evaporative emmisions equipment then you should run it all. It won't affect performance. But i would say, by now, most charcoal canisters have passed their "Use-By Date".

You can easily braze up the pin hole, but if the whole unit is scaly rusty like mine, its probably like that inside as well. Many other Mopars used this type i think, Darts, Chargers from 72 on, so shouldn't be hard to find a better one at a wrecking yard. Pain to get out though!

I blew through the canister tube into the tank and no air would go in. I blocked three of the four tubes on the other end and blew into the four one. Very little air escaped out the charcole pipe. I assumed that there should be very good flow at that point.

I have a WANTED add on a few sites looking for a new one. One guy in Michigan said he will send me his for free...I'd just have to pay the shippiing but I don't know if that one is any better. I was hoping someone from down south would have one. I imagine that anything tht is up in the rust belt will look like the one I have.

Does anyone have one of these that they can test out for me. I just need to know if there should be a lot of airflow out to the charcole canister or if just a little bit is correct.

Never tried one but i would imagine that airflow through it would be pretty low otherwise it would not be able to do its job??

I have no idea how much airflow there is supposed to be. That's why it would be nice to have another one tested.

If you just need a minimal amount of flow...mine if probably OK. I'll just have to fix the pinhole. It cleaned up really nice in the EvapoRust. It may need another 24 hour soak and should be ready for some metal work. The nice thing about the EvapoRust is that it is cleaning the inside out too.

You could live without it if you use a vented filler cap or vent the filler neck.

i may have misled u there. dont 4get how it operates: the carcoal cannister tube has vacuum applied to it. But only allows enough to purge the stored gases, then shut off. you can test this with you mouth, sucking and blowing and if its working correctly you will see what i mean. It needs to be sealed to prevent the gasses escaping into the atmosphere, its a one-way valve that only operates for a second or two.

dave-r wrote:You could live without it if you use a vented filler cap or vent the filler neck.

Even better.

It's all cleaned up and the internal valve seems to be working properly now. I see what you mean when you said to suck and blow on the tube. It does only open for a short time before it closes again.

Here's my next question.

I took the tank to a radiator/gas tank repair shop today and he said it would cost over $15 to braze the two pinholes. I do have access to another one...they want $20 plus shipping for it but even then I don't know if that one is any beter than mine.

Can I solder the pinhole areas or is the solder just going to flow into the holes and not do anything? Can I use some sort of epoxy that isn't affected by fuel or do I need to have the holes brazed?

Solder only works on copper and copper alloys.

Brazing will work.

You can get epoxy that is fuel proof. usually sold as tank repair paste.

Brazing is better and easy to do.

Thanks Dave...I'll just call up my father-in-law and see if he can fix it for me. I'm sure he has some brazing rods laying around.