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Vapor Separator?
#280681
04/07/09 06:57 PM
04/07/09 06:57 PM
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Joined: Jan 2005
Posts: 1,647
IL
71383beep
OP
top fuel
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OP
top fuel
Joined: Jan 2005
Posts: 1,647
IL
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In the process of getting my car ready for this season and I thought that I would tackle the latest wierd issue i had with it last year.
It ocasionally would have very hard starting issues after sitting for a half hour or so after a good drive. It almost seemed like it was flooded. I would have to floor it to get it started, but sometimes even that would not help. I would crank and crank and then let it sit for 30s and then she would fire up.
I was thinking vapor lock, but the carb has a phenolic spacer and the line is AN from the pump to the carb and not near the headers.
Someone recently sugested that I install a vapor separator. I have the 5/16 inch vent line for it, but it goes to the evap contraption behind the left wheelwell and the 5/16" nipple on the tank is capped. This is a CA car if that matters and I have the 3/8" steel fuel line.
I do suspect a venting issue though too because when i pull the fuel cap to put gas in there is a ton of back preassure which I know is not good.
Will a properly installed vapor separator resolve these issues?
'73 GK6 Challenger Rallye - 340 4-Speed
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Re: Vapor Separator?
[Re: Challenger 1]
#280683
04/07/09 07:25 PM
04/07/09 07:25 PM
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Joined: Jan 2005
Posts: 1,647
IL
71383beep
OP
top fuel
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OP
top fuel
Joined: Jan 2005
Posts: 1,647
IL
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Yep,
71 charger Super Bee - 383 auto.
'73 GK6 Challenger Rallye - 340 4-Speed
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Re: Vapor Separator?
[Re: 71383beep]
#280684
04/07/09 08:10 PM
04/07/09 08:10 PM
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Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
Challenger 1
Too Many Posts
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Too Many Posts
Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
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To do it right, you need three fuel lines. One for feed, one for the return from the vapor separator. Both of these connect to the sending unit. The third goes from the valve cover breather to the rear of the car to the tank vapor separator in the trunk. This is how my N95(Cal) 71 E body is layed out. I'm not sure about your car but I'm thinking it is the same. I am sure you want your vapor separator returning to the sending unit. And yes it does work because I have two cars setup this way and drive with AC on in the hottest weather. Here's two of them, I haven't added the third fuel line yet in this picture.  Vapor separator that goes in the trunk.Notice how it has 5 nipples on it and the tank only has 4 vapor hoses.   Third line in place that goes from the VC breather to the rear separator.  And then you know where the V.S. goes up front right? Be sure to check that it has a #54 or so size hole for the return too. There was some bad ones out there I heard with no restriction in the return.  That's where it goes on the motor(fuel pump bolt) 
Last edited by Challenger 1; 04/07/09 08:46 PM.
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Re: Vapor Separator?
[Re: 71383beep]
#280685
04/07/09 09:25 PM
04/07/09 09:25 PM
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Joined: Oct 2005
Posts: 9,065
Milwaukee, WI
In_The_Pink
master
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master
Joined: Oct 2005
Posts: 9,065
Milwaukee, WI
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Quote:
In the process of getting my car ready for this season and I thought that I would tackle the latest wierd issue i had with it last year.
It ocasionally would have very hard starting issues after sitting for a half hour or so after a good drive. It almost seemed like it was flooded. I would have to floor it to get it started, but sometimes even that would not help. I would crank and crank and then let it sit for 30s and then she would fire up.
I was thinking vapor lock, but the carb has a phenolic spacer and the line is AN from the pump to the carb and not near the headers.
Someone recently sugested that I install a vapor separator. I have the 5/16 inch vent line for it, but it goes to the evap contraption behind the left wheelwell and the 5/16" nipple on the tank is capped. This is a CA car if that matters and I have the 3/8" steel fuel line.
I do suspect a venting issue though too because when i pull the fuel cap to put gas in there is a ton of back preassure which I know is not good.
Will a properly installed vapor separator resolve these issues?
You should try a new gas cap first, IMHO. Gas caps are designed to allow air in when too much vacuum is present or too much pressure is present, and from your description, it sounds like the cap isn't releasing the excess pressure. Gas caps seem to be one of those parts which most people never replace, but they do wear out. 
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Re: Vapor Separator?
[Re: Challenger 1]
#280686
04/07/09 09:28 PM
04/07/09 09:28 PM
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Joined: Oct 2005
Posts: 9,065
Milwaukee, WI
In_The_Pink
master
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master
Joined: Oct 2005
Posts: 9,065
Milwaukee, WI
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Quote:
Vapor separator that goes in the trunk.Notice how it has 5 nipples on it and the tank only has 4 vapor hoses.
'71-'72 B-vans used a similar system (four vent tubes originating at each top fuel tank corner, all leading to the vapor separator), with the fifth line from the separator leading to the carb, where excess vapor is drawn in and burned.
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Re: Vapor Separator?
[Re: In_The_Pink]
#280687
04/07/09 09:33 PM
04/07/09 09:33 PM
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Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
Challenger 1
Too Many Posts
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Too Many Posts
Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
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Quote:
Quote:
In the process of getting my car ready for this season and I thought that I would tackle the latest wierd issue i had with it last year.
It ocasionally would have very hard starting issues after sitting for a half hour or so after a good drive. It almost seemed like it was flooded. I would have to floor it to get it started, but sometimes even that would not help. I would crank and crank and then let it sit for 30s and then she would fire up.
I was thinking vapor lock, but the carb has a phenolic spacer and the line is AN from the pump to the carb and not near the headers.
Someone recently sugested that I install a vapor separator. I have the 5/16 inch vent line for it, but it goes to the evap contraption behind the left wheelwell and the 5/16" nipple on the tank is capped. This is a CA car if that matters and I have the 3/8" steel fuel line.
I do suspect a venting issue though too because when i pull the fuel cap to put gas in there is a ton of back preassure which I know is not good.
Will a properly installed vapor separator resolve these issues?
You should try a new gas cap first, IMHO. Gas caps are designed to allow air in when too much vacuum is present or too much pressure is present, and from your description, it sounds like the cap isn't releasing the excess pressure. Gas caps seem to be one of those parts which most people never replace, but they do wear out.
Very good point 
I forgot to mention, Have you ever removed the gas cap and see if it makes a difference?
But nothing should be "capped off" on your fuel system for it to work right.
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Re: Vapor Separator?
[Re: Snoopy]
#280694
04/08/09 02:07 PM
04/08/09 02:07 PM
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Joined: Sep 2003
Posts: 3,426
weymouth,mass.
meepmeep70
master
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master
Joined: Sep 2003
Posts: 3,426
weymouth,mass.
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not to highjack,but can we post a diagram for 70 road runner 440? i'm buying new tank this week,my old tank had the vent running up into the trunk and back out,only one line ran up to the fuel pump,do i need to run two lines up front and install a vapor seperator? back when the second third tube came off tank to 6"hose with a bolt in it  .thanks for your help,and sorry to highjack  ,it was kinda similial question
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Re: Vapor Separator?
[Re: 71383beep]
#280695
04/08/09 05:10 PM
04/08/09 05:10 PM
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Joined: Oct 2008
Posts: 765
Shoreline, Washington
72roadrunnergtx
super stock
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super stock
Joined: Oct 2008
Posts: 765
Shoreline, Washington
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The b-bodies in 71 thru mid-year 72’ had the fuel tank vapor separator located in the driver’s side rear wheel well. The hard line running up to the breather cap in 71’ is the tank’s vent line. Any fuel vapors evaporating from the tank while the car was at rest would be collected in the crankcase to be consumed at next start up via the PCV valve. Any vacuum present in that line would be equal to that of the crankcase while running nothing more. Mid–year 72’ had a redesigned tank vapor separator much smaller and located just forward of the tank. Enclosed carb bowl vents in 71’also connected to the breather cap for the same reason. 72’ had these evaporative lines connected to the charcoal canisters. Not to be confused with the fuel supply line vapor separators that were installed to resolve vapor lock conditions on some big-block/California cars and as mentioned required a return line.  72 1/2' and up vapor seporator  Try leaving the air cleaner off while as it sits hot for the 30mins, see if it starts any better. Quite a few six-packs suffer from vapors evaporating/collecting in the air cleaner after a good heat soak condition making for an over-rich hot start-up within a window of about 15min to about an hour or so. The combined surface area of the fuel in the 3 bowls contributes to a higher than average evaporation rate.
Last edited by 72roadrunnergtx; 04/08/09 05:12 PM.
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Re: Vapor Separator?
[Re: 71383beep]
#280697
04/08/09 06:04 PM
04/08/09 06:04 PM
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Joined: Oct 2008
Posts: 765
Shoreline, Washington
72roadrunnergtx
super stock
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super stock
Joined: Oct 2008
Posts: 765
Shoreline, Washington
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The three nipple breather; tank vent line would connect to a 5/16”nipple. Bowl vent line is 3/8” and the air cleaner hose is something like 7/8”.  BTW a vapor lock condition would lead to fuel starvation at the carb not the flooded condition I interpreted from your first post. The smaller tank vapor separator pictured above for 72 ˝’ replaced the one you have in the LR wheel well.
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