Second fuel line.. what is it for?

[dpascual1986]

1973 240z. What is the other line on the fuel rail for, the one not connected to the fuel filter? Is it a feed to the carbs or is it a return?

I want to cap it, im trying to clean up my engine bay but it kinda looks important

[Mark Maras]

It's a return line. According to some of the threads I've read it can be eliminated if you use a fuel pressure regulator. 3 1/2 lbs. seems to be what everyone runs on SUs.

Mark in Portland

[dpascual1986]

It's a return line. According to some of the threads I've read it can be eliminated if you use a fuel pressure regulator. 3 1/2 lbs. seems to be what everyone runs on SUs.

Mark in Portland

thanks. I flipped through the forums using "eliminating fuel return" and there are mixed opinions about it. I guess I shouldn't eliminate -if unsure, dont fix what's not broke.

[Stanley]

Removed return line two years ago, no problems. I have a different fuel rail that doesn't pick up as much heat from the engine as the stock one. Fuel pressure usually stays between 3.4 and 3.9 psi while driving. I have seen pressure drop to about 2.5 psi once on the freeway (parking lot conditions) in hot weather, that might have been a warning of impending vapor lock. Only time it ever vapor locked it was 120F, when I still had the return hooked up.

Thought about using the return line as an extra fuel tank vent (might need to run a line to the air cleaners or under the car to prevent gas smell), or use it as a return for a fuel pressure regulator. For now it's capped.

[Mark Maras]

Yeah. I agree. I'm leaving mine on my 260. I thought about changing it but I'm trying not to get caught up in the " as long as I'm here I should". When I really thought about it, that is so far down my list of to-dos that it may never get done. It's a long list. But for those who truly have Z fever it doesn't matter, It's a labor of love with huge rewards that few understand.

Mark in Portland

[dpascual1986]

Removed return line two years ago, no problems. I have a different fuel rail that doesn't pick up as much heat from the engine as the stock one. Fuel pressure usually stays between 3.4 and 3.9 psi while driving. I have seen pressure drop to about 2.5 psi once on the freeway (parking lot conditions) in hot weather, that might have been a warning of impending vapor lock. Only time it ever vapor locked it was 120F, when I still had the return hooked up.

Thought about using the return line as an extra fuel tank vent (might need to run a line to the air cleaners or under the car to prevent gas smell), or use it as a return for a fuel pressure regulator. For now it's capped.

might be a stupid question but what is vapor lock? Are you running stock mechanical fuel pump? Can you show a pic your "different" fuel rail? I was planning to cut the hard lines along the firewall and attach a hose from the firewall to the carbs directly -eliminating the two hard lines on the left side of the engine bay (when looking at it head on).

[Stanley]

Just have mechanical fuel pump for now. Removed the electric one at the tank and put a filter there instead. The fuel rail is welded steel tube connected with a short length of fuel hose to a hose barb on the fuel pump.

Right under the glass filter see where I capped the return line. Doesn't look great. The other hose from the mechanical fuel pump goes to a fuel pressure gauge under the glove box.

Seems to me your idea is OK but I'm not the expert.