Fuel Pressure Bypass Regulator Connection

[Ricks72Chlgr440]

I have a 72 Challenger with a fuel tank that has emission tubes that are capped off. It does not have the vapor separator if it ever had one. I want to install a fuel pressure regulator that has a bypass so I can send excess fuel back to the tank. The tank fuel level sender does not have a return line so I'm wondering if I can use one of the capped off lines for the return?

 

[Challenger RTA]

I too had the same thought. Just haven't a reason to yet. I considered a tee at the rubber line with a check valve to prevent feeding to the separator. Also consider if for a fuel vapor separator return if needed. The diagram below is 71. Using it for reference. It shows a vent-liquid return line. Not sure which one on a 72 would feed back to the tank. for what you want to do. You would have to know what line feeds back into the tank.

 

[pschlosser]

from the factory, your 1972 should have had the vapor separator. it is part of the ECS system that became mandatory in 1971. and it sounds like it's been removed at some point, and your ECS tank has the four vent connections capped off.

if so, any of the vents will probably work as a fuel return. All four of those lines feed back into the top of the tank.

that liquid vapor separator at the rear of the car is pretty useful, it's too bad it's been removed. were it still in place, an alternate idea is using the 426/440 fuel sending unit, because it includes the return line fitting for use with the vapor separator from the front of the car. in some cases, there were two fuel-vapor separators, the ECS one on all cars (with ECS) and the vapor-lock-preventing one at the mechanical fuel pump and 426/440 cars.