Fuel Return Line

[Ricks72Chlgr440]

I have a 72 Challenger with a fairly new tank that has 4 vent tubes that are currently capped off. I want to start using a return line from the fuel pressure regulator but am not sure which of the vent tubes to connect to.

 

[Challenger RTA]

Here's a start. to figure out what you want to do.
The ECS systemm had nothing to do with the vapor separator.
The vapor separator/filter was used on all '70 440 4bbl - 440 6bbl - HEMI cars.

The return line from the vapor separator goes to the sending unit with or without ECS.
the vapor separator goes into the tank

The ESC has no provision for what you want to do. It returns vapor from what I understand.
I think this is what you have to do.

 

[pschlosser]

You can use, of course, one of the four ECS fuel tank vapor line for your return. I'm not sure its designed for pressurized liquid fuel return, but it will probably work. You can road test the concept using 30 feet of rubber tubing, to connect the fuel pump to the tank and give it a try without a big investment of time.

The factory returns fuel using a different line.

I believe the correct fuel sending unit for 440 and 426 cars with the vapor return line from the engine, have a second nipple fitting on the sending unit. The second fitting is used for fuel return. The unit may also come with 3/8 fuel line instead of the 5/16 found on most other engine models.

There is a also factory hard line, found only on the 440/426 cars with the engine fuel separator. They make this line aftermarket, if you want to install and use that for fuel return, it may look darn good and original.

The presence or absence of this fuel vapor separator return line, has helped me many times, over the years, in confirming and validating claims about 440 and Hemi cars. Without a VIN to confirm, we can drop to our knees, and look under the car for the K-frame skid plate and vapor separator return line. When present on a 'Cuda, they indicate an original 440 or Hemi car.

 

[Steve340]

Use the one labelled Vent - Liquid Return Line indicated in the picture RTA has posted.

 

[Ricks72Chlgr440]

Thanks guys. The tank and sender are almost new so I would hate to replace the sender just to get a return line. I may try one of those vent nipples to see if that works as a return. If I have issues I guess I'll have to pony up for a different sender. On a slightly different but related note, have any of you had good results with a particular regulator that has a return line? The pump I will be using is a Carter P4070. I would only use a regulator for the return line, as the pump is set ~ 6 PSI and really does not need a regulator.

 

[cuda joe]

if you use the vent line don;t use the one that goes to the engine bay. instead run a line to one from the tank by the right rear wheel and cap off the other side

 

[swarthout]

Hello everyone, don’t mean to hijack this thread but I’ve hit a wall on my rebuild. I have a 1973 Dodge challenger with a 340. I’ve routed the main fuel line and what I believe is the vent line which starts at the vent separator near the tank and ends at the front passenger side of my engine bay. My question that I can’t find an answer to is, do I need a return fuel line and if I do what does it connect to in my engine bay? I know where it starts at my gas tank sending unit but I have no clue where it ends up. Also, just confirming I’m supposed to have three fuel related lines running from rear to front. I appreciate any help.

 

[Steve340]

340 cars only had 2 lines. The main fuel feed to the pump and the fuel tank vapor saver line connected to the valve cover breather.
This info is correct for 1971 but things may have changed for 1973 but I don't think so.
The third line is for the "fuel vapor separator" and is only fitted to the 440 and 426 cars and is the one that returns liquid fuel to the tank.
My 340 car the fuel tank sender only has one 3/8 nipple.
There is a full description of both systems in the Fuel System section of the factory service manual.

 

[swarthout]

340 cars only had 2 lines. The main fuel feed to the pump and the fuel tank vapor saver line connected to the valve cover breather.
This info is correct for 1971 but things may have changed for 1973 but I don't think so.
The third line is for the "fuel vapor separator" and is only fitted to the 440 and 426 cars and is the one that returns liquid fuel to the tank.
My 340 car the fuel tank sender only has one 3/8 nipple.
There is a full description of both systems in the Fuel System section of the factory service manual.

Outstanding! Much obliged!