Fuel line question ..

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orangecrush

orangecrush

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Will this work : 73 Dart has a tank with vapor return line, I'm running a new 3/8 line to pump can I cap off the nipple for the vapor line or should I run it "elsewhere" for ventilation ?
 
I am doing the same thing and just did a search on the subject the other day. It seems the concensus was just to buy a vacuum cap and cap it off.
 
How is the tank vented if it's capped off? Weren't the pre-smog cars built w/ vented caps? Don't I remember some cars having a vent tube run up in the trunk and then back out? I don't remember if they were Mopes, though. Also, if the cap is the vent, would a high horsepower engine use gas faster than the vent could work? :dontknow:
 
That's my concern - my 67 Dart had a vent tube that ran up the filler neck so....how will this tank be vented if I plug that there nipple thingy !
 
The fuel tank must be vented somehow or you will end up with a vacuum condition in the tank as fuel is drawn out.

Run a hose somewhere unobtrusive where fumes won't get into the passenger compartment or the hose won't get in water and cap it off with a small fuel filter like the cheap clear sintered brass ones. If you're creating serious HP, cap it off with a small K&N breather filter.
 
I capped mine,(71 Duster) and had no problems. I'm quite certain my cap is vented.
The end of the vent must be higher than the fuel level will ever be.
If you top it off up to the gas cap, whatever is above the level of the vent opening will be lost.
How do I know this?
 
If my memory serves me, those cars that had a vapor return line up the side of the fill tube, the vent attached to the top of the fillerneck.
That would actually be back into the tank, so the cap must be vented.
My 68 Runner has that ventline up into the trunk and back out into the frame rail.
But the filler on that is behind the license plate, below the level of the vent.
 
Run no vent on a fuel tank and see what happens......I did on an old Ferd by accident! You'd be suprised the vacuum a mechanical pump will pull, sucked the center of the tank right up like a squashed pop can. Needles to say I drove home with a nice split in the tank after I popped the cap!! Dumb kid I was!!(well I was driving a Ford)
 
All I am saying is that the sending unit I took out did not have an extra vent on it so I am going to cap the new one off. If the tank is vented somewhere else, that's great, but I'm not going to add an additional vent.
 
ramcharger said:
The fuel tank must be vented somehow or you will end up with a vacuum condition in the tank as fuel is drawn out.

Run a hose somewhere unobtrusive where fumes won't get into the passenger compartment or the hose won't get in water and cap it off with a small fuel filter like the cheap clear sintered brass ones. If you're creating serious HP, cap it off with a small K&N breather filter.
Click to expand...

I'll go this route - now just need to figure where I can terminate where fumes won't be an issue AND it's above filler neck, hmmmm ... any suggestions ?
So all these things did back in the day was vent back into engine bay, into the charcoal cannisters ?
 
orangecrush said:
I'll go this route - now just need to figure where I can terminate where fumes won't be an issue AND it's above filler neck, hmmmm ... any suggestions ?
So all these things did back in the day was vent back into engine bay, into the charcoal cannisters ?
Click to expand...

Yep, into the canister then out a hose to a valve on the carb to be burned in the combustion chambers. Prior to this style of evaporative emission control it was just vented to the atmosphere. If your cap is vented (like a few others said) you're good to go and don't have to worry about it unless you're running a huge amount of fuel.
 
I vented the cap on my duster. took it apart and drilled two small (3/16) holes in the brass part. then added a way for it to vent through the handle on the outside of the cap. No pressure build up problems for me. I'm not autocrossing the car, so I haven't had any seepage problems either.
 
dusterdon said:
I vented the cap on my duster. took it apart and drilled two small (3/16) holes in the brass part. then added a way for it to vent through the handle on the outside of the cap. No pressure build up problems for me. I'm not autocrossing the car, so I haven't had any seepage problems either.
Click to expand...

I knew some MacGyver type would eventually chime in - thanks
 
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