Fuel line cap problem/solution

[Spin'em75]

Went to give my '75 duster a good wax and clean...kept noticing a faint gas smell every time I'd bend over to wipe the tire well...lord behold, had a pretty good gas leak going on and my driveway was starting to puddle up. Noticed it was coming from this gas (vacuum?) Line located underneath and near the alternator. The rubber was torn and brittle already. Ran quickly to the auto store and purchased another set of random caps and a hose clamp. Leak stopped.

My question is: is this setup normal? If it is, is there another solution instead of a rubber cap and hose clamp? Hate for this to happen again, and I've never encountered this problem before. Any help or input would be appreciated.

 

[67Dart273]

That is part of the evap emissions controls and IS THE ONLY "functional" vent for the tank. The fuel caps have what is known as "pressure vacuum" reliefs. These are relief valves, NOT operational vents. Get into your shop manual and read the section on the evap in the emissions chapter as well as the chapter covering fuel tanks.

Generally, that line must be "up high" in the engine bay so that it will not siphon. Some guys plumb them into the non vacuum section of the PCV system, AKA whatever is leading to the air cleaner

My opinion, if you are going to pull or replace the tank, look up the very simple 69/ earlier vent system, which is a tube connection welded up high in the filler tube. They work well

 

[Spin'em75]

That is part of the evap emissions controls and IS THE ONLY "functional" vent for the tank. The fuel caps have what is known as "pressure vacuum" reliefs. These are relief valves, NOT operational vents. Get into your shop manual and read the section on the evap in the emissions chapter as well as the chapter covering fuel tanks.

Generally, that line must be "up high" in the engine bay so that it will not siphon. Some guys plumb them into the non vacuum section of the PCV system, AKA whatever is leading to the air cleaner

My opinion, if you are going to pull or replace the tank, look up the very simple 69/ earlier vent system, which is a tube connection welded up high in the filler tube. They work well

Thanks. My handbook will be here soon. I've got an uncle who will be handing his down to me. In the meantime since I don't have it, is this setup normal, and is it common for these rubber caps to be there or be replaced? Is the fuel only passing through since the line was busted?

 

[67Dart273]

No idea. These systems changed a bit almost every year, and so did the cap. You need to read that manual. I don't have anything later than a 74 manual. I did have I think a 76 manual, but I've had a bit of a house fire. That and many others are now gone

 

[Kendog 170]

Earlier style. Vent line goes into the raer frame rail.
1967-1969 Dodge Dart Valiant Gas Fuel Tank Filler Neck Tube fits 67 68 69 | CHBFNT718 | Taiwan

 

[67Dart273]

That tube, tho, will not fit a Duster

 

[Kendog 170]

Opps. Good point. Still that style

 

[67Dart273]

The newer cars, the tube is installed from the outside of the fender, AKA the tube flange is on the outside when installed. This means if you convert your tube to the old pre-70 style (Actually some 70's did not have evap) you cannot have a vent fitting that protrudes from the fill tube. If you can silver braze, etc, it is not much of a job to braze a fitting into the tube that is flush. If you do so, pull the tube and carefully measure the clearance between the tube and the fender hole so you know how much protrusion you can deal with.

The older ones, the tube was stuck "down in" from the trunk, then brought back up and out to enter the fender hole from the inside of the trunk.

 

[H22A4]

Does your 75 Duster still have the charcoal canister?

Here’s how the system works (from 75 FSM).

Don’t listen to anyone who says a charcoal canister is power robbing equipment; it is a passive system that doesn’t rob a single hp nor impact performance in any way. It’s there to eliminate the gas smell you have now.

 

[Spin'em75]

Does your 75 Duster still have the charcoal canister?

Here’s how the system works (from 75 FSM).
View attachment 1716401510View attachment 1716401511

View attachment 1716401512


Don’t listen to anyone who says a charcoal canister is power robbing equipment; it is a passive system that doesn’t rob a single hp nor impact performance in any way. It’s there to eliminate the gas smell you have now.

Thanks a bunch for this! So my duster does not have the canister. The vent line/overfill limiting valve is sealed off by a rubber cap and clamp hose. I just did the same after noticing the rubber became torn off/brittle randomly to prevent the leak that was occurring. Is it recommended to maybe purchase and go back to the charcoal cannister?