Vapor Recovery Line - do you need it?

[Flexicoker]

I need to replace all the rusted out hardlines that run down the tunnel, since the asbestos cement goop they were incased in holds water real nice.

 

Sooo... This is a '73, and I really don't want to have to weave the vapor recovery line in there since the engine/tranny and everything else are in place. The brake/fuel lines shouldn't be as hard.

 

So for those of you that disconnected it, did you just plug the line at the tank? Did you route a vent tube with a check valve somewhere? Did it stink like gas after you did it?

 

Thanks,

Eric

[Tony D]

If your tank is sealed properly with all the vapor lines intact, you will need that line to have a filter on the end so the tank can 'breathe' when the fuel is siphoned out driving down the road.

I saw a clubmembers' 73 die on the side of the road with 'no fuel pressure' after 20 minutes of highway driving. Opened the gas tank thinking his 'fuel gauge was bad' and got the 'giant sucking sound'... Car ran fine for another 25-30 minutes till it started stumbling again---then we realized the filler neck was sucked right down FLAT! We were confounded by how it happened, he had just had "all the hoses replaced out back here" and figured 'waitaminit'---went up front and there was a cap on the vapor line in the engine bay. "It was capped like that years ago---I've never had a problem before!" Shore nuff, with the cap off, he drove from Palm Springs all the way back to LA without even a stumble...he ended up sticking a K&N filter from a promotional keychain on there so it looks good. LOL

[WizardBlack]

If your tank is sealed properly with all the vapor lines intact, you will need that line to have a filter on the end so the tank can 'breathe' when the fuel is siphoned out driving down the road.

I saw a clubmembers' 73 die on the side of the road with 'no fuel pressure' after 20 minutes of highway driving. Opened the gas tank thinking his 'fuel gauge was bad' and got the 'giant sucking sound'... Car ran fine for another 25-30 minutes till it started stumbling again---then we realized the filler neck was sucked right down FLAT! We were confounded by how it happened, he had just had "all the hoses replaced out back here" and figured 'waitaminit'---went up front and there was a cap on the vapor line in the engine bay. "It was capped like that years ago---I've never had a problem before!" Shore nuff, with the cap off, he drove from Palm Springs all the way back to LA without even a stumble...he ended up sticking a K&N filter from a promotional keychain on there so it looks good. LOL

 

And a car idling long enough is a fire hazard. Pull the line out back to the rear and install a breather at the back of the car and AWAY from the exhaust. Please don't leave it open in the engine bay.

[Tony D]

If you do it out back, I would run the hose up to the vapor recovery tank, make a 'double loop' and then do the venting outside the passenger area, don in the area by the filler neck, behind that plate you can remove in the Right Rear Wheel Well. The tall rise and double loop will prevent the expansion of gasoline on a hot day and full tank from rising to the point where it can puke out the end of a hose simply vented overboard from the vent fitting on the tank, and lifted minimally to clear the top of said tank.

 

Some of the Non-US cars were vented in that area simply by a vent tube off the filler neck---though it's a straight hose in that application, and moulded into the filler neck. I have one of those setups on my 73, and no vapor recovery line.

[JMortensen]

And a car idling long enough is a fire hazard. Pull the line out back to the rear and install a breather at the back of the car and AWAY from the exhaust. Please don't leave it open in the engine bay.

I think that might be overstating the danger a bit. There are lots of cars on the road with small fuel leaks and very few of them burn up.

 

I had a related embarrassing incident at the track once. I had dead headed my fuel system and had not done anything with the return line. I mean nothing. It was just the fuel line sitting there disconnected in the engine bay. So I came in from a session and popped the hood and there was fuel everywhere in the right side of the engine compartment. Apparently under braking the gas was running forward and out the line and dumping onto the fenderwell. I stuck a bolt in the return line and secured it with a hose clamp and that served as my fix for the next 4 or 5 years...

 

I don't recall where the vent line attaches to, but if you're pulling some g's on deceleration you might be dribbling some gas through that K&N in the engine compartment.

[cygnusx1]

I drove my WRX since day one to 100K miles with a factory installed fuel leak. The fuel would puddle on the block about four inches in front of the turbine. The dealer would not fix it, the NHTSA, Subaru of North America, all said it was a NON-ISSUE. The smell of fuel in the cold weather was unbearable. I had to run with recirc vents or it would suck fumes into the cabin. There were about 2000 reported and documented cases at the NHTSA of the same issue. The case was closed, Subaru dealers were issued a technical service bulletin, and were told to charge customers for the parts and labor to fix/replace a defective fuel line......anyway despite the bitter feelings....100K miles of it and still no fire. I used to hope it would burn. I ended up biting the bullet and having it fixed by a dealer for $500 because my wife was pregnant and would not ride in the "gas car" anymore.

 

The fuel line fix required several hours of labor because the leaky factory hose clamp was buried under the intercooler and intake manifold.

 

Despite the high risk of fire with the puddle of fuel and the red hot turbine, none of them ever burned up.

[zcarnut]

...Some of the Non-US cars were vented in that area simply by a vent tube off the filler neck---though it's a straight hose in that application, and moulded into the filler neck. I have one of those setups on my 73, and no vapor recovery line.

 

The earliest USA 240Zs were built like that as well. I have number 1841 and it even lacks the inside expansion tank above the filler tube. No vent tube down the transmission tunnel was used and no vent valve (next to the carbs). Even the back of the air filter housing is different.

[Flexicoker]

Sweet, thats what I wanted to hear. I'm probably going to plug it and run a vented gas cap... Or just run it up and back down.

 

High five!

[JMortensen]

The earliest USA 240Zs were built like that as well. I have number 1841 and it even lacks the inside expansion tank above the filler tube. No vent tube down the transmission tunnel was used and no vent valve (next to the carbs). Even the back of the air filter housing is different.

Hmm... wonder if that's a CA thing. I know 1439 had the expansion tank. I think 472 did as well, but I can't quite be positive. They were both CA cars.

[WizardBlack]

I think that might be overstating the danger a bit. There are lots of cars on the road with small fuel leaks and very few of them burn up.

 

That may be but I have personally seen one. It totalled the car. A WRX as a matter of fact. All it takes is something else in the engine bay to start a spark/small fire/etc. and it will take off. In the case of the one I saw, it was aftermarket wiring that wasn't rated well enough. I'd suspect that on a Z you would have the same risk since it has fusible links rather than proper fuses. That was enough to light off the dense fuel vapors and POOF. I remember seeing the puddle of aluminum on the ground under the front of the car. That is what USED to be some of the fuel rails, various aluminum bits, etc. I even got to see about 12 little steel wires wrapped around all the accessory pullies. All the rubber in the belt had burned off and left the spindly little steel wire reinforcements left on the pullies.

I'd recommend the above poster's proposed vapor neck. If you have sealed the line off well enough, you will build vacuum in the gas tank as you use fuel on a trip and end up sucking so hard it collapses the filler neck and eventually the car shuts off since the pump can't get anything. That is assuming everything is still sealed up like it should be. I would run a small elevation hump and then terminate in a K&N at the right rear of the car.