Stupid question on fuel line configuration

JimD

JimD

Waiting for Godot...
Moderator
I have a stupid question on fuel lines. I ask just to convince myself that even I can't screw this up. Here it is.

With a carb'd car that has input and return fuel lines, is it possible to run the car with the input and return reversed on the carb? The car runs pretty well around town and on the highway, but for the life of me I can't find a diagram anywhere that says which line is which. So I have to assume, always dangerous, that since the car is running the lines are correct as currently configured.
 
JimD said:
ISo I have to assume, always dangerous, that since the car is running the lines are correct as currently configured.
Click to expand...

The correct positioning is for the return to go on the carb nipple that points more towards the fuel tank, while the inlet goes to the nipple that is more on the passenger side of the carb. If the two lines are of different sizes, the return is the smaller one.

The car will probably run OK if you mess this up, the routing will just be a bit awkward.

The car will NOT run OK if you mix up the two lines at the fuel tank end.
 
Thanks Eric

Thanks Eric.

OK. I "think" it is all set up right. The return is hooked to the smaller tube coming from the tank, so I will leave it be. The car is running well, I think I just need to do some more adjusting on the carb's idle mixture.
 
No camera today

Hi Hussein,

My camera is dead today and I can't find any batteries around here. Oh well, I think the hoses are fine as is going by Eric's comments. I have been looking at those hoses for months and I am not sure why they bug me so much. :nuts:
 
The lines are different size with the supply line larger at 5/16" and the return line smaller at 1/4". The fittings on the tank and carb are different size to match the difference in size of the hoses. I suppose if you work at it hard enough you could get them reversed.
 
Now I need to check the tank

Thanks carl

You and Eric have me questioning the tank end now. I will do that later today. A quick look in the trunk of the 124 last night has me thinking the small nipple in the sender is connected to the large line running forward and them large nipple is hooked to the smaller line.

There are lots of hoses with the vents and connections for the charcoal cannister back up front as well. A more careful examination is needed.
 
Seems the lines were crossed at the tank.

I went to MWB and looked up a 124 sedan sending unit and found a good picture. The fat tube has a sock on the lower end of the pickup tube. The skinny tube feeds into a rubber hose which terminates at the same "depth" as the sock, which I guess explains why it will run with the lines in either configuration.

I really can't tell a huge difference in the way the car is running, but I think I need to start the carb adjustment procedure over before declaring a minor victory. I took the opportunity to replace the hoses at the tank while I was working there. I will say it started much easier off the fat tube.
 
I need to move this thread Larry

Thanks Larry,

If I would get off my ass and get new batteries for my camera it would have been obvious that this wasn't an X related issue. Sorry. :tomato:

I started this thread in the WF because I thought it would just be a general question on the effect of reversing the fuel input and return lines. The thread has gotten more specific to my 124 Special as I have kept poking at the problem. I will move it over to the "Front-Engine rear drive" forum where it probably belongs at this point.
 
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