71 Fuel Tank with 5 vent lines on side

[71RR4406]

I have a 71 Plymouth CA car.
I am replacing the tank with the 4 vent model and going to connect to factory standards as long as the Evaporator tank is functional.

So the question is not with the new tank or how it needs to be hooked up.
I get all of that. Evap line to breather, fuel return to correct filter. Etc.

The problem is my existing tank has 5 vents on the side.
What is this and why?
I can not find any inf on this.

Please post your knowledge of this, what seems to be some sort of rare tank.

 

[6872n73]

Out of the driver side of the tank? or the front of the tank? (Just behind the shock. Mount(

 

[TopBanana72]

My understanding is that b bodies prior to April 1972 (at least Chargers, not sure about Plymouths) had the tank with the 5 vents on the side. Hoses went from the tank to an evap expansion tank positioned inside the driver's side wheel well. This is why the wheel well is larger on the driver's side (looking at it from the trunk). One line went from this expansion tank up to the 3-nipple breather on the valve cover (1971) or to the charcoal canister (1972). Your 71 should have this expansion tank (again, I am assuming Dodges and Plymouths would be the same). After April 1972, the vents were relocated to the front of the tanks and tank was redesigned with an expansion area on top of the tank, thus eliminating the separate expansion tank. Both styles of tank are available in repop from what I've seen.

 

[71RR4406]

So i have the 5 vents on the side, and 5 vents on the evap tank.
One line on the evap goes to the front, to the breather.
That leaves 4 lines to the tank.
Then i have one open on the tank.

So where would that go?
Could it be a fuel return?

 

[TopBanana72]

Correction.. Now that I think of it, the post April 1972 cars may have an additional expansion tank which is smaller, mounted to the frame near the front of the tank where the 4 vent lines are. The vent lines go into this "vapor separator" tank and then one line up to the front charcoal canister. Your 71 still would not have this front separator tank, but should have the wheel well mounted one.

 

[TopBanana72]

So i have the 5 vents on the side, and 5 vents on the evap tank.
One line on the evap goes to the front, to the breather.
That leaves 4 lines to the tank.
Then i have one open on the tank.

So where would that go?
Could it be a fuel return?

Not sure. Are you confirming you have the wheel well mounted evap tank?

 

[71RR4406]

Yes rear evap wheel well tank.
Everything i find and every manual comes up with the 4 vent tank.
I just can not figure the 5 vents on thw actual tank.

 

[TopBanana72]

mmm, well I know I have the 5 side vents on mine (like your pic). The 5 vents might be a 1972 thing and maybe 71's had 4. I know there is a diagram in my 1972 FSM showing the system. I'll have to dig that up and find it. It's a little late for me to go find it now, but you have me curious. I know they changed things yearly during the emissions years. I'll see what I can find out. A lot of people don't know about this evap stuff because they are mostly ignored or not restored to factory spec. It's a shame because there is no performance hit on keeping the evap system.

 

[TopBanana72]

California cars might have had some emissions weirdness too..

 

[71RR4406]

Thanks.. let me know.

Also this was an original CA car early 71 before the LA plant shut down.

Also the car had a few owners from what i can tell, and it may not even be the original tank.

 

[T2R9]

Interesting, never seen one with 5 ports. Both my 71 and 72 manuals only show the 4 as mentioned.

 

[pjm8047]

Here are some pics from the 71/72 manuals.
First two are from the 71 manual and the other two the 72 manual

 

[T2R9]

Same as my manuals. Both show 4 port tanks.

 

[pjm8047]

Im thinking it was the wrong tank probably wasn’t original to the car

 

[71RR4406]

It is strange.
Everything else on the tank looks identical to the 4 port new one I have.

 

[TopBanana72]

Yes, others are right. I was wrong. Mine too really has 4 ports like the diagram, not 5.

Answer then to original question: I have no idea. The only thing I can think of is California emissions weirdness.

 

[pjm8047]

Some stuff I found

 

[6872n73]

Just for reference pics. You might see if you can get a camera to see where or what the fifth one does.
Curious minds want to know now.

 

[71RR4406]

I am taking the tank down in a week or so. I will see if I can find out. I have a Remote Camera i will put in the tank.

 

[pjm8047]

From the 70-71parts manual. Looks like only one tank was available for it.