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73-87 Chevy _ GMC Trucks => Fuel Systems and Drivability => Topic started by: chevy_guy on August 30, 2012, 08:10:11 am

Title: Fuel Vapor Line???
Post by: chevy_guy on August 30, 2012, 08:10:11 am: I am rebuilding a 79 custom deluxe with a rebuilt and mildy modified 350, I was looking at my gas pump and it has three lines that go to it, the fuel line, return line and a vapor line. I was woindering do I actually need the vapor line...can it be capped or even pulled...If not what does it actually do that I need to keep it....NOW I am by no means an expert engine builder so, lets be nice :)
Title: Re: Fuel Vapor Line???
Post by: slammed79 on August 30, 2012, 09:30:01 am: The vapor line probably runs to your charcoal canister on the core support, and needs to be there for emissions/inspection purposes if your state/county requires them.
Title: Re: Fuel Vapor Line???
Post by: bd on August 30, 2012, 10:04:23 am: Post a picture of the pump.
Title: Re: Fuel Vapor Line???
Post by: chevy_guy on September 05, 2012, 09:17:49 am: Here is the pump with the lines labeled, I am asking if the vapor line can be plugged or removed.
Title: Re: Fuel Vapor Line???
Post by: bobcooter on September 05, 2012, 09:35:34 am: I have a 79 also. I removed all the emissions stuff when I rebuilt mine. I left the charcol canister and a vapor line going to it. I think the vapor line I am talking about comes from the fuel tank. I will try to remember to check and see how mine is set up and let you know.
Title: Re: Fuel Vapor Line???
Post by: zieg85 on September 05, 2012, 09:43:28 am: 2 inlets on the pump and one outlet going to the carb?
Title: Re: Fuel Vapor Line???
Post by: bobcooter on September 05, 2012, 01:19:25 pm: I think one is a return line to the tank to recieve any unused fuel. The vapor line to the charcol canister comes from the tank.
Title: Re: Fuel Vapor Line???
Post by: Captkaos on September 05, 2012, 01:31:29 pm: The three ports are the Supply, Vapor and return. The vapor should return to the tank. It is there to help prevent vapor lock. If you won't need it, you can cap it off.
Title: Re: Fuel Vapor Line???
Post by: chevy_guy on September 05, 2012, 02:45:34 pm: Vapor lock??? ???
Title: Re: Fuel Vapor Line???
Post by: Captkaos on September 05, 2012, 03:16:41 pm: fuel can get heated in hot summer days and turn to vapor basically putting a pocket of fuel vapor in the fuel line starving the carb of fuel not allowing the engine to run and make it hard to crank. This is a normal occurance on low pressure carb'd engines.
Title: Re: Fuel Vapor Line???
Post by: oldschoolgmc on October 02, 2012, 09:22:23 pm: I took the charcoal canister (and the rest of the emissions stuff) off my truck. I bought a cheap fuel filter for a riding lawn mower and capped the end of the vapor line. This allows it to breath without allowing bugs and such to get inside the line.
Title: Re: Fuel Vapor Line???
Post by: 454Man on October 03, 2012, 12:42:45 pm: I plugged mine into the timed vac port on my edelbrock 1406. Haven't had any problems or smelly gas fumes yet :-)