Fuel filler door conundrum

[Marlon L]

I must be overlooking something here. It has been a few years since I purchased the car and took it apart, so I don't know if it was always like this. I have the flip open fuel filler door, and it doesn't seal against the filler neck. The seal on the door is 1" from the filler neck when closed?? I understand it's supposed to seal on the the filler neck of course. The flange on the filler neck is welded, so I can't pull it further out of the tank from what I can see. Any insights?


Thanks,
Marlon

 

[Mopars & Missiles]

Where's your gas cap? That seals the filler tube.

 

[Marlon L]

Is there supposed to be an 1/4 turn cap on the filler well then?

 

[Challenger RTA]

Did you have a Charger before? It's not a Charger.

 

[Marlon L]

No, this cap was on my 73 Challenger

 

[Challenger RTA]

There is a rubber cup on the fuel door. It is for vibration and a tight fit. Not to seal the filler neck.

 

[Challenger RTA]

Is there supposed to be an 1/4 turn cap on the filler well then?

Yes.

 

[Marlon L]

That rubber seal does not come in contact with the filler neck though in mine. There would definitely be evaporation issues as well as dirt and the moisture getting in to the filler neck. It seems that the filler neck should stick out of the car another inch in order to seal against that rubber, but it's welded to the flange on the inside. If I used the original cap, It looks like it would fit fine, but this chrome door sits off the car and inch.

 

[Mopars & Missiles]

 

[Mopars & Missiles]

Do it your way, don't believe what us dummies tell you.

 

[Marlon L]

That's what I was thinking I needed to do... Put an actual cap inside like that. The car didn't have one on it when I bought it so it would have been evaporating and getting contamination in it. It amazes me that the tank was as clean as it was when I took it out... It was so shiny inside It looked like something you could cook in.

 

[Challenger RTA]

Do it your way, don't believe what us dummies tell you.

Been there. Had the engine running and but not in gear. Wondering why I wasn't going anywhere.

 

[Steve340]

The "internal" cap is vented for vacuum/pressure and to allow for the correct operation of the vapor saver system.
They were on EBAY.

 

[Mopars & Missiles]

The "internal" cap is vented for vacuum/pressure and to allow for the correct operation of the vapor saver system.
They were on EBAY.

The gas cap is "NON-VENTED". This is clearly shown in the photos above. The filler tube itself, just inside the trunk, has provisions for the fuel system venting which goes down through the trunk floor and into the frame rail where it is open to the atmosphere.


Edit: At least this is true on a 1970 model, others may vary.

 

[Steve340]

Perhaps on your car that is correct. But I have checked both the 1970 and the 1971 factory service manuals and it shows the vented pressure/vacuum cap is required for the ECS system in both years.
In any case it is going to be better having the vented cap in my opinion, no matter what system is on the car.
I can't see the down side of using the vented cap if he needs to buy one. Might as well get the ECS compatible one.

 

[Mopars & Missiles]

Perhaps on your car that is correct. But I have checked both the 1970 and the 1971 factory service manuals and it shows the vented pressure/vacuum cap is required for the ECS system in both years.
In any case it is going to be better having the vented cap in my opinion, no matter what system is on the car.
I can't see the down side of using the vented cap if he needs to buy one. Might as well get the ECS compatible one.

Yes, that's the problem with many systems on these cars, there are variations due to local regulations. For the most part I suspect that the Cleaner Air System (CAS) cars far outnumber the Evaporation Control System (ECS) cars. ECS was a California requirement if I recall correctly? If so, that ECS system would be in place on far far fewer cars than what were sold in the other 49 states. But yes I agree with you, I don't see the harm in using a VENTED cap on either system, provided you are not trying to be 100% OEM correct with the car in question.


And yes, the diagram of the CAS system I posted is correct for my car.

 

[moparleo]

The fuel cap cover was only Factory available on 70-71 cars.
Naturally it will attach to 72 -up cars but was never an option.
Big emission changes started in 1972 across the board.
Safety changes starting in 73 like 5 mph bumpers on all passenger cars.

 

[moparleo]

I would also recommend that you change the 4 mounting screws to anti theft type.
Only takes a few seconds with a cordless drill/ screw driver to steal your cap/cover.