Fuel lines - why have 2 ?

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Johnny71dusty

Johnny71dusty

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So I have have 4 A body’s and none of the slant cars have had a return fuel line but my 318 cars have .

I have a 318 challenger too and wondering if it’s really a must for have the return line or not . I get why it’s there . But is it a must ? Because many cars in late 60s early 70s didn’t have one either .

I just don’t want to run a second line if I don’t have too.
 
Is it actually a return line or a vapor line? I'm guessing it's a vapor line. My 68 A-body has 1 fuel line. The tank is vented at the fuel filler tube. My 73 Challenger has two lines. One is the feed and the other is the vapor line. The vapor line runs from the vapor separator back by the tank, to the charcoal canister in the engine compartment. The tank is vented through the charcoal canister.

If you look at your second line, my guess is that it runs to a vapor separator and doesn't actually route fuel back to the tank.
 
Johnny71dusty said:
So I have have 4 A body’s and none of the slant cars have had a return fuel line but my 318 cars have .

I have a 318 challenger too and wondering if it’s really a must for have the return line or not . I get why it’s there . But is it a must ? Because many cars in late 60s early 70s didn’t have one either .

I just don’t want to run a second line if I don’t have too.
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Car has 2 two lines going all the way up front . I don’t know if it’s a vapor line or a return line . My tank also has 4 vents up above the rear . My A body’s I don’t think have ever had that either
 
Here is what the vapor separator looks like on my 73 318 Challenger. The 4 lines coming out of the tank go into the separator. Then there is 1 line that comes out of the separator and goes to the engine compartment. That is a vent/vapor line. That is the line the tank vents through.
1002013.jpg
 
Johnny71dusty said:
Return line
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It is NOT a return line unless someone "made" it so. It is the TANK VENT and ties into the evap emission system in the car. These changed year to year, so it's important to look up the exact year to see what -is- what. You can download service manuals for free up through 74 from MyMopar.
 
This system first appeared on CA state cars in '70. I'm not sure if it was "all" federal in 71 or not, but some 71's had it and by 72, all cars did. Again this changed over the years

Of particular annoyance is the change in fuel filler caps The emissions caps ARE NOT VENTED. They are known as "pressure vacuum" caps and they have spring loaded reliefs to relief vacuum or pressure above certain levels. Ordinarily the tank is vented through the 1/4" line going up front

I believe Steve, OldManMopar first posted this photo:

abody-gas-caps-67-70-70-cal-and-71-72-74-75-76-copy-jpg-jpg.jpg
 
New fuel with ethanol boils at a low temperature. This boiling cause a rich mixture due to the floats not working properly. So even if your car didn't come with a return it is a good Idea to add one. Keeping the fuel flowing prevents boiling.
cures the problem. All carbureted mopars 85-87 came with a return filter to try and correct this issue.

I added a return to the Duster and what a difference in EGT's and performance

DSCF0171.JPG


Steve 098.JPG
 
Back to the original question. Look for N95 on the fender tag or broadcast sheet.
 
Johnny71dusty said:
So I don’t need that second one if it’s a vent/ vapor line only ? Correct ?
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What do you mean "you don't need it?" IT IS THE VENT. Of course you need it, or you are going to have to "build" the 69/ earlier old style vent. You need a tank vent of some sort
 
67Dart273 said:
What do you mean "you don't need it?" IT IS THE VENT. Of course you need it, or you are going to have to "build" the 69/ earlier old style vent. You need a tank vent of some sort
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It doesn’t need to run all the way up the car to engine bay though

DE152304-C9FB-47A5-B5D5-E77D9A630B1F.png
 
Johnny71dusty said:
It doesn’t need to run all the way up the car to engine bay though

View attachment 1715843638
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The problem is that if you end the line "down under" it may siphon. It does not hurt anything in the engine bay. You need either leave it there or rebuild it to the old 69 type You can easily get yourself into a situation. You can end up with an unvented tank, a vent that siphons fuel overboard and so on. That line does not weigh much and it does not hurt a thing, and it is necessary.
 
67Dart273 said:
The problem is that if you end the line "down under" it may siphon. It does not hurt anything in the engine bay. You need either leave it there or rebuild it to the old 69 type You can easily get yourself into a situation. You can end up with an unvented tank, a vent that siphons fuel overboard and so on. That line does not weigh much and it does not hurt a thing, and it is necessary.
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The tank has 4 vents already , I’m very confused on why one needs to go all the way t the front of the car . I’ll buy the line I guess . If my 5 A body’s didn’t have have the affine line going all the way up front not have 4 vents tubes at the tank I don’t get why a 74 challenger needs it.
 
My cars tank is gone and the 4 into 1 air separator thing I’m seeing in pics is gone and my thought is my other cars never had this / why does this one need it. Why did my other 7 vintage mopars and my current duster not have this and I’ve never experienced vapor lock .
 
OK I've tried to explain this to you. This is the last time

1...Go to MyMopar and download a 69, a 72, and the 73 service manuals and look at that section on the evap emissions and you will see the changes over the years

2...ALL TANKS need a vent

3...Up through 70-71 when tanks were vented BY the vent tube in the filler, the vent connected UP HIGH in the filler tube and THAT CONNECTION formed a "vacuum break" so the thing did not siphon. The only time that vent would overflow is if the tank was somehow extremely full and parked on a "sidehill" with the filler side down, and ONLY THEN it would spill fuel at the vent until the level dropped below the vent connection, and stop

4....None of the caps are truly vented. Up through the evap cars, the cap was SEALED. Caps after that are pressure/ vacuum "relief" and they are NOT considered vented. RELIEF

5...With the evap tanks there MUST be a way to prevent siphon. Some models had the tank in the trunk "vapor separator" and this allowed some fuel to come up into that tube and then drain back to the tank. THE LINE GOING to the front comes "up high" in the engine bay

6...The later cars/ tanks had a vapor separator IN the tank, and only ONE vent line leaving the tank. With those model cars it is more important than ever to keep the line to the front UP HIGH to prevent siphon.

That is all I have to say. You do not seem to want to believe anybody. So do whatever you want. I do not care
 
67Dart273 said:
OK I've tried to explain this to you. This is the last time

1...Go to MyMopar and download a 69, a 72, and the 73 service manuals and look at that section on the evap emissions and you will see the changes over the years

2...ALL TANKS need a vent

3...Up through 70-71 when tanks were vented BY the vent tube in the filler, the vent connected UP HIGH in the filler tube and THAT CONNECTION formed a "vacuum break" so the thing did not siphon. The only time that vent would overflow is if the tank was somehow extremely full and parked on a "sidehill" with the filler side down, and ONLY THEN it would spill fuel at the vent until the level dropped below the vent connection, and stop

4....None of the caps are truly vented. Up through the evap cars, the cap was SEALED. Caps after that are pressure/ vacuum "relief" and they are NOT considered vented. RELIEF

5...With the evap tanks there MUST be a way to prevent siphon. Some models had the tank in the trunk "vapor separator" and this allowed some fuel to come up into that tube and then drain back to the tank. THE LINE GOING to the front comes "up high" in the engine bay

6...The later cars/ tanks had a vapor separator IN the tank, and only ONE vent line leaving the tank. With those model cars it is more important than ever to keep the line to the front UP HIGH to prevent siphon.

That is all I have to say. You do not seem to want to believe anybody. So do whatever you want. I do not care
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So with all that - a line all the way to the front of engine , it’s not needed as they didn’t do it for many many years . . That’s what you’re saying. But it needs to vent somewhere yes I know this. But it doesn’t need 4 lines and one going up to engine bay. High In engine bay is still lower than fill tube


3...Up through 70-71 when tanks were vented BY the vent tube in the filler, the vent connected UP HIGH in the filler tube and THAT CONNECTION formed a "vacuum break" so the thing did not siphon. The only time that vent would overflow is if the tank was somehow extremely full and parked on a "sidehill" with the filler side down, and ONLY THEN it would spill fuel at the vent until the level dropped below the vent connection, and stop
 
Then just rip it off and throw it in the ditch. You already knew what you were going to do before you ever came here.
 
Are you looking for advice or are you simply expecting people to validate your incorrect assumptions?
 
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