How to block off fuel return line in Classic Industries Fuel Sending Unit.

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73Dart340Sport

73dart340
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Hello Mopar experts,

I’m reinstalling a Classic Industries fuel sending unit with a 3/8 fuel line and a either 5/16” or 1/4” return line. I am running a carb and do not need the return line and therefore I would like to plug it. (See attached picture) I used a rubber vacuum plug as a temporary fix however I’m guessing that this is not the brightest idea. Any ideas as to what I should do?
62E16CA1-F9EB-4E0D-8F21-EDF144DC2739.jpeg
 
I would block it off with a return line.
 
I used the old style 50/50 lead solder from the inside, after I crimped it down to a slot. Worked well. Later solders like 95/5 do not stick as well.
 
I may want that return for the future! A cap like that is not good!

Get a short piece of line with a better solution, like a shoulder bolt in the end that can be clamped well!
 
I don't even like those caps for vacuum. Years ago I had one blow off with a backfire on a cold morning, and one other had "gone soft" and the fitting sucked a disc the size of the tube into the engine. Did not seem to hurt the engine but the 3/8 fitting caused a ridiculous air leak

I know it's ugly, but a short hose with a sawed off bolt and a pair of clamps WORKS.

Or take it apart and solder it shut. You might "trial fit" and see if some bolt size will accidently "almost fit" perhaps you can tap the inside of the fitting, "dope up" the bolt with some good sealer, and screw it in there.
 
Hello Mopar experts,

I’m reinstalling a Classic Industries fuel sending unit with a 3/8 fuel line and a either 5/16” or 1/4” return line. I am running a carb and do not need the return line and therefore I would like to plug it. (See attached picture) I used a rubber vacuum plug as a temporary fix however I’m guessing that this is not the brightest idea. Any ideas as to what I should do?View attachment 1715512411


The rubber cap like in your picture has been on mine for years with a hose clamp. Probably not the best solution, but it works. Replaced the fuel sender recently, it was still in good shape, so I put it back on.
 
The rubber cap like in your picture has been on mine for years with a hose clamp. Probably not the best solution, but it works. Replaced the fuel sender recently, it was still in good shape, so I put it back on.

Its your car! Keep the insurance up, JMO!
 
Bad if you want 3/8” line feed. About the only choice, be safe!!
 
I just asked the same question a few days ago and after a lot of research and conversations I agree with rusty you should use it for the return line and use a fuel filter with the third nipple. There was a video posted in my thread that can explain it better than me. I will find it and repost it here
 
I liked the video and plan to check out more of his videos today! However my understanding is that the 5/16 tube that I have plugged in the picture is the fuel return line which I would need if I had an electric fuel pump and EFI. The Vent line is run to the vent fitting which is on top of the tank which would allow for vapor expansion. My reference is the 1973 Dodge Chassis service manual 14-54 through 14-59. I wanted to clarify that the vent return fitting is on top of the tank and the 5/16 tube protruding out of the have of the sending unit is for fuel return. Feedback??

I’ve been married for 30 years, I’m used to being wrong!
 
Have you done
I don't even like those caps for vacuum. Years ago I had one blow off with a backfire on a cold morning, and one other had "gone soft" and the fitting sucked a disc the size of the tube into the engine. Did not seem to hurt the engine but the 3/8 fitting caused a ridiculous air leak

I know it's ugly, but a short hose with a sawed off bolt and a pair of clamps WORKS.

Or take it apart and solder it shut. You might "trial fit" and see if some bolt size will accidently "almost fit" perhaps you can tap the inside of the fitting, "dope up" the bolt with some good sealer, and screw it in there.
 
I plugged mine with a sealed piece of rubber hose and clamped it on tight with a hose clamp. I have not had any issues with leaking at this point.
 
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