EVAP on a 72 C3
Thread Starter
Instructor
Joined: Feb 2005
Posts: 101
Likes: 0
EVAP on a 72 C3
Hey everyone,
I was thinking of plugging the EVAP lines on the driverside of the fuel tank. I was planing on using an electric fuel pump. So I figured while the tank was out ill clean it up and just cap off this EVAP thing on the tank. This should cause any fuel flow problems will it. Im also doing away with the vapor line and just having one SS Braided 6an FUEL line. Do I need to cap off the EVAP line also? Is this a vacuum source leak area?
thanks
randy
I was thinking of plugging the EVAP lines on the driverside of the fuel tank. I was planing on using an electric fuel pump. So I figured while the tank was out ill clean it up and just cap off this EVAP thing on the tank. This should cause any fuel flow problems will it. Im also doing away with the vapor line and just having one SS Braided 6an FUEL line. Do I need to cap off the EVAP line also? Is this a vacuum source leak area?
thanks
randy
Melting Slicks
Joined: Aug 2006
Posts: 3,429
Likes: 20
From: Kingston Ontario
Well, your tank will be getting smaller that way. You don't have a vented gas cap. With a vented gas cap your garage will always smell like gas so thats why I'm leaving my drivers line hooked up..
Le Mans Master
Joined: Aug 2006
Posts: 7,419
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
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I'm pretty sure that if you eliminate the vapor line you will need a vented cap or you can collapse your gas tank.
Thread Starter
Instructor
Joined: Feb 2005
Posts: 101
Likes: 0
as for if everything is there...........the original fuel line and vapor/return? line was removed a year ago for a turbo project which never amounted to anything. So now Im going to use a non return style fuel pump. Isnt that 2nd line on the passenger side a return line???
The EVAP lines are still present but old and I have no idea the condition of the canister. Doest the canister have a vacuum source?
thanks for the help.
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
The return line is for fuel vapor not fuel. These systems are carbureted not high pressure fuel injection.
The vapor canister has charcoal in it to absorb fuel vapors from the gas tank. It also has a line for the PCV valve.
cc
The vapor canister has charcoal in it to absorb fuel vapors from the gas tank. It also has a line for the PCV valve.
cc
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
The fuel return line simply loops cool fuel from the tank to the fuel pump and back, to prevent vapor lock. Both the main fuel line and return are on the passenger's side of the frame.
The Evap system, on the driver's side of the frame provides a slight bit of vacuum in the fuel tank to prevent the "whoosh" of escaping vapors when removing the fuel cap, which took place prior 1971 model cars. Heat from the exhaust system and agitation from driving, would create pressure in the tank, hence the "whoosh" which was thought to pollute the air.
Vacuum for the Evap is sourced from the carb or intake.
If you remove the Evap system, you'll need to cap off the nipple on driver's side of the fuel tank. You'll also need to replace your existing non-vented fuel cap with a vented cap (1970 or ealier). A vented cap has a check valve which allows air into the tank to replace spent fuel, but won't allow fumes out for obvious reasons (unless there's a lot of pressure built up). If you shake a vented cap, you can hear it rattle like a PCV valve. And you'll need to plug the vacuum source for the Evap system.
Good luck!
The Evap system, on the driver's side of the frame provides a slight bit of vacuum in the fuel tank to prevent the "whoosh" of escaping vapors when removing the fuel cap, which took place prior 1971 model cars. Heat from the exhaust system and agitation from driving, would create pressure in the tank, hence the "whoosh" which was thought to pollute the air.
Vacuum for the Evap is sourced from the carb or intake.
If you remove the Evap system, you'll need to cap off the nipple on driver's side of the fuel tank. You'll also need to replace your existing non-vented fuel cap with a vented cap (1970 or ealier). A vented cap has a check valve which allows air into the tank to replace spent fuel, but won't allow fumes out for obvious reasons (unless there's a lot of pressure built up). If you shake a vented cap, you can hear it rattle like a PCV valve. And you'll need to plug the vacuum source for the Evap system.
Good luck!
Last edited by 73, Dark Blue 454; Oct 30, 2009 at 12:21 AM.
Le Mans Master
Joined: Jun 2008
Posts: 5,284
Likes: 235
From: Rockledge FL
fuel pump has an in from tank, out to carb, and return to tank
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Instructor
Joined: Sep 2009
Posts: 135
Likes: 2
From: Waterbury CT.
WHY, WHY, WHY ??? You will gain nothing by blocking off lines to the tank. If your going to use an electric pump; be sure you have a by-pass line going back to the tank or be prepared to have your car park it self on the side of the road in hot weather . VAPOR LOCK. As stated before, that allows cool fuel from the tank to circulate through the system and prevent vapor lock. Good luck.
Team Owner
Joined: Sep 2006
Posts: 31,202
Likes: 4,287
From: Westminster Maryland
Hi Randy,
I'll repeat what a couple of people have already said... be careful about doing away with the fuel separator and charcoal canister, that can lead to a gas smell in the garage.
Regards,
Alan
I'll repeat what a couple of people have already said... be careful about doing away with the fuel separator and charcoal canister, that can lead to a gas smell in the garage.
Regards,
Alan
Thread Starter
Instructor
Joined: Feb 2005
Posts: 101
Likes: 0
The fuel return line simply loops cool fuel from the tank to the fuel pump and back, to prevent vapor lock. Both the main fuel line and return are on the passenger's side of the frame.
The Evap system, on the driver's side of the frame provides a slight bit of vacuum in the fuel tank to prevent the "whoosh" of escaping vapors when removing the fuel cap, which took place prior 1971 model cars. Heat from the exhaust system and agitation from driving, would create pressure in the tank, hence the "whoosh".
Vacuum for the Evap is sourced from the carb or intake.
If you remove the Evap system, you'll need to cap off the nipple on driver's side of the fuel tank. You'll also need to replace your existing non-vented fuel cap with a vented cap (1970 or ealier). A vented cap has a check valve which allows air into the tank replace spent fuel, but won't allow fumes out for obvious reasons (unless there's a lot of pressure built up). If you shake a vented cap, you can hear it rattle like a PCV valve. And you'll need to plug the vacuum source for the Evap system.
Good luck!
The Evap system, on the driver's side of the frame provides a slight bit of vacuum in the fuel tank to prevent the "whoosh" of escaping vapors when removing the fuel cap, which took place prior 1971 model cars. Heat from the exhaust system and agitation from driving, would create pressure in the tank, hence the "whoosh".
Vacuum for the Evap is sourced from the carb or intake.
If you remove the Evap system, you'll need to cap off the nipple on driver's side of the fuel tank. You'll also need to replace your existing non-vented fuel cap with a vented cap (1970 or ealier). A vented cap has a check valve which allows air into the tank replace spent fuel, but won't allow fumes out for obvious reasons (unless there's a lot of pressure built up). If you shake a vented cap, you can hear it rattle like a PCV valve. And you'll need to plug the vacuum source for the Evap system.
Good luck!
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
Thread Starter
Instructor
Joined: Feb 2005
Posts: 101
Likes: 0
you guys are great!
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
We have two discussions going at once.
The fuel return line has nothing to do with venting the fuel tank or the Evap system. If you remove the return line (perhaps your aftermarket fuel pump doesn't have a return line provision), simply plug the nipple on the passenger's side of the fuel tank.
If you're going to keep your Evap system, then keep your original 'closed' (non-vented) fuel cap.
Again, these are two different systems and functions.
The fuel return line has nothing to do with venting the fuel tank or the Evap system. If you remove the return line (perhaps your aftermarket fuel pump doesn't have a return line provision), simply plug the nipple on the passenger's side of the fuel tank.
If you're going to keep your Evap system, then keep your original 'closed' (non-vented) fuel cap.
Again, these are two different systems and functions.
