Why are my vent lines leaking?

[DynaBro]

Soldier connections at the nipple/tank junction are probably cracked.

Nope. It really did just end up being a pressure issue due to the short line being converted to a return line, and the return nipple being blocked off. Restoring a secondary venting path by loosening the gas cap stopped the seeping. Hard to believe that little vent is so important, but with a full tank it apparently can be. At least that appears to be the case as of right now. Drove an hour yesterday to lower the fuel level some, no drips so far. I will be taking it out for a last drive of the season today with a new vented cap to confirm. For now a vented cap should suffice. Then this summer I'll get a new sending unit from Vans and replumb the whole thing.

 

[R/T Boy 67]

Food for thought. Reproduction sending units are notoriously inaccurate, so you might want to repair the one you have.

 

[DeltaV]

A few general comments on the pictures posted earlier.

1) looks like old hoses. Replace them.

2) do the old hoses have markings to indicate they are rated for gasoline? You can check after you replace and throw them in the trash can.

3) Take a look at Gates Barricade hose. It's compatible with all types of hose.

4) worm drive clamps...not stock items...used when the stock hoses were replaced with unknown hose grade in the past. I used to use the worm drive style of clamp on all types of hose, but not any longer.

I no longer use these on fuel hose.

I now use the following types on fuel hoses. Accessibility sometimes dictates which one to use.

You will need a special clamping/crimping tool/pliers for the last one. Buy extra of this last style in case you get the crimp wrong.

 

[DeltaV]

Why would the tank be pressurizing while parked in a cool environment?

I'm assuming there's no clean and easy method of checking for line blockage?

The return goes to the front and is hooked up in pic.

View attachment 1760989

My favorite hose cluster. Not!

 

[DynaBro]

Food for thought. Reproduction sending units are notoriously inaccurate, so you might want to repair the one you have.

I read the Vans ones were the best and redesigned to fix that? Not the case?

 

[DynaBro]

My favorite hose cluster. Not!

View attachment 1762234

Yeah that's going to need to be addresses as well. Any idea what he was thinking connecting the return line through the feed filter? Just from the flow standpoint alone that's counterintuitive. I doubt the return fuel even ends up in that filter at all.

 

[DynaBro]

A few general comments on the pictures posted earlier.

1) looks like old hoses. Replace them.

2) do the old hoses have markings to indicate they are rated for gasoline? You can check after you replace and throw them in the trash can.

3) Take a look at Gates Barricade hose. It's compatible with all types of hose.

4) worm drive clamps...not stock items...used when the stock hoses were replaced with unknown hose grade in the past. I used to use the worm drive style of clamp on all types of hose, but not any longer.

I no longer use these on fuel hose.
View attachment 1762219

I now use the following types on fuel hoses. Accessibility sometimes dictates which one to use.

View attachment 1762220View attachment 1762221View attachment 1762222
You will need a special clamping/crimping tool/pliers for the last one. Buy extra of this last style in case you get the crimp wrong.

Actually first item on my to do list today. That's WHERE I am driving.

 

[Sixpactogo]

Whoever bastardized your fuel system is to blame for your issue. Your car came with a 3/8" fuel line and 1/4" return from the factory. Mopar did this to alleviate vapor lock problems. When you decide to fix it properly, you will need to get the correct vapor separator that restricts the fuel returning to the tank. (the filter setup you have more than likely does not have that restricted orifice) Here is a picture of the correct separator. (part # 1739230) It is the black canister mounted to the fuel pump bolt. Also you will need to either replace the sender or if your gauge reads correctly now, I would repair your return tubing where that idiot pinched it off. While you are at it, blow some air through that vent tube that ends up in the frame rail to make sure it vents properly and then put that unvented gas cap back on. In the mean time leave the cap loose or put on a vented one.

 

[DynaBro]

Whoever bastardized your fuel system is to blame for your issue. Your car came with a 3/8" fuel line and 1/4" return from the factory. Mopar did this to alleviate vapor lock problems. When you decide to fix it properly, you will need to get the correct vapor separator that restricts the fuel returning to the tank. (the filter setup you have more than likely does not have that restricted orifice) Here is a picture of the correct separator. (part # 1739230) It is the black canister mounted to the fuel pump bolt. Also you will need to either replace the sender or if your gauge reads correctly now, I would repair your return tubing where that idiot pinched it off. While you are at it, blow some air through that vent tube that ends up in the frame rail to make sure it vents properly and then put that unvented gas cap back on. In the mean time leave the cap loose or put on a vented one.

View attachment 1762252

Those came on 383 cars?

 

[Sixpactogo]

I assumed your car was a 440 car since the sender appears to have a 3/8" fuel tube and a 1/4" return tube that is pinched off. If your car is a factory 383 car it would have had a 5/16" fuel tube with no return. Looks like we need more information. Does your car have the 3/8" fuel line and 1/4" return mounted to the passenger side or did the PO add all of that stuff?

 

[DynaBro]

I assumed your car was a 440 car since the sender appears to have a 3/8" fuel tube and a 1/4" return tube that is pinched off. If your car is a factory 383 car it would have had a 5/16" fuel tube with no return. Looks like we need more information. Does your car have the 3/8" fuel line and 1/4" return mounted to the passenger side or did the PO add all of that stuff?

Upgrades is my guess. It’s as highly optioned as a factory 383 came performance wise with the A31 package but as far as I know that had no influence on fuel lines. But you’re correct about the larger lines, which he mentioned in his service diary.

My plan was to fix the sending unit and route the return back there to the small nipple where it belongs. The only thing I’m scratching my head about is why he routes the return line from the pump back into the filter shared with the feed line. But I did some research and it’s common. Lots of people saying helps equalize pressure. If it works I guess it works but I would have fed the return line direct to the tank.

 

[Sixpactogo]

That setup with the filter is the same as the vapor separator and is much cheaper than the mopar separator. Biggest problem is the Mopar vapor separator has a smaller orifice in that 1/4" nipple that returns excess fuel back to the tank. It was designed to stop vapor lock after shut down. The fuel left over in the pump would boil and cause vapor lock. The return line eased that problem. The issue with those aftermarket filters is there is no regulating orifice in most of them and it allows too much fuel to go back to the tank starving your engine. You didn't mention that your engine was starving so it is possible that your filter has some reduction flow. Mopar fixed a lot of problems before we even knew they could be a problem. However, it seems like we try to cheap charlie the system and create more problems. Case in point.....Look at the picture of my six pack engine. Notice the serpentine belt system? I thought it was the cats meow until I had overheating problems. Turns out the smaller crank pulley and larger water pump pulley was slowing down the flow of coolant causing the water to stay in the engine too long. Mopar designed the correct pulley sizes and I screwed it up causing my own problems blaming it on the radiator, fan and water pump not doing their job when it was my doings all along. I think if you get your car back to the way Ma built it, your problems will go away too.

 

[DynaBro]

Which for me would be the correct sending unit with smaller lines. But actually only smaller rubber portions because the steel lines are stock and correct. Which will be fairly easy if the sending unit job goes well.

 

[Sixpactogo]

Yeah. If you already have the return line going back to the tank, I suggest getting the mopar vapor separator and fixing that return nipple on the sender. Verify your vents are not plugged. Your issues should go away.