Need info on a return line back to the fuel tank - The 1947 - Present Chevrolet & GMC Truck Message Board Network

streetmaster42 · 03-05-2008, 05:24 AM

Need some advice on putting a return line on the fuel system. The 76 GMC had an I6 in it, and it only had just 2 lines coming out of the fuel tank when i tore my truck down, i guess one of them was a return line, not real sure about that one. I've always thought that it went to the charcoal canister, its only been 10 yrs since i tore this thing down LOL. I replaced the I6, with a 350 sbc, and it has 110gph Holley mech pump on it. Im putting the stock tank back on soon, and im not sure if i need a return line with my set up or not. Since i replaced the I6 with a 350sbc, should i then replace the 2 line fuel pump, with a 3 line fuel pump, im not really up on all this fuel system stuff. (Please Advise)

James McClure · 03-05-2008, 02:57 PM

Street: Check the size of the lines on the sending unit. If both lines are 3/8" one line goes to the fuel pump and the other is a tank vent and it just goes over the side of the tank and has a vent cap on it. If one line is 1/4", it's supposed to go back to the fuel pump in which case the pump will or should have 3 connections on it. The 1/4" connection on the pump is really sort of a pressure regulator and also keeps fuel circulating back to the tank to cool keeping evaporative emmissions down. You can use a 3 line sender with a 2 line pump, just cap the 1/4" fitting on the sender, but if you have a 3 line pump you have to use a 3 line sender or replace the pump with a 2 line pump to match the sender. Hope this helps

jim

streetmaster42 · 03-06-2008, 01:53 AM

The stock pump that i got for my truck at AutoZone has 2 lines on it. I figured that one line went to the carb, and the other went to the tank. Theres also a 2 lines coming out of the sending unit, (1# 5/16)(2# 3/18) and the 5/16 line on the sending unit has a piece of hose with a bolt screwed into it.

James McClure · 03-06-2008, 02:57 AM

streetmaster: OK, yours is matched correctly 2 for 2. Only problem is the line with the bolt in it. The bolt has to come out and have a vent end put in. The end to which I refer looks alot like the one for the rear end. If it's not there I'm not sure where you would get one, but your local Chevy store might be able to help you out. jim

streetmaster42 · 03-06-2008, 05:03 AM

Ok im starting to get whats going on with this emissions thing. Ill take that line with the hose on it, (Off) and run it back to the charcoal can, and be done with that. I now have to figure out if the PSV on my 350 splits off with one hose going to the char canister, and the other to the carb. Or if the PCV just goes to the carb. I know that the EGR goes to a TVS switch, but the hose from the TVS goes to the carb, aswell as the vacume advance, the mod valve for the TH350. The big problem im dealing with is, i have 1405 Edelbrock performer series carb that only has 2 small vacume port in the front of it. The one on the left is constant, and the one on the right is not. Do i (T) off the vacume advance with the hose from the TVS hose. Theres also the hose from the charcoal canister that goes to the carb, not sure if it needs to be hooked to a constant port or not. I guess what i need is a detailed list of how i can make all this work with the Edelbrock carb.

03-05-2008, 05:24 AM	#1
streetmaster42 Registered User Join Date: Aug 2007 Location: Uniontown,PA Posts: 60	Need info on a return line back to the fuel tank Need some advice on putting a return line on the fuel system. The 76 GMC had an I6 in it, and it only had just 2 lines coming out of the fuel tank when i tore my truck down, i guess one of them was a return line, not real sure about that one. I've always thought that it went to the charcoal canister, its only been 10 yrs since i tore this thing down LOL. I replaced the I6, with a 350 sbc, and it has 110gph Holley mech pump on it. Im putting the stock tank back on soon, and im not sure if i need a return line with my set up or not. Since i replaced the I6 with a 350sbc, should i then replace the 2 line fuel pump, with a 3 line fuel pump, im not really up on all this fuel system stuff. (Please Advise)

03-05-2008, 02:57 PM	#2
James McClure One shot, one kill. Join Date: Dec 2007 Location: Saratoga Springs NY Posts: 859	Re: Need info on a return line back to the fuel tank Street: Check the size of the lines on the sending unit. If both lines are 3/8" one line goes to the fuel pump and the other is a tank vent and it just goes over the side of the tank and has a vent cap on it. If one line is 1/4", it's supposed to go back to the fuel pump in which case the pump will or should have 3 connections on it. The 1/4" connection on the pump is really sort of a pressure regulator and also keeps fuel circulating back to the tank to cool keeping evaporative emmissions down. You can use a 3 line sender with a 2 line pump, just cap the 1/4" fitting on the sender, but if you have a 3 line pump you have to use a 3 line sender or replace the pump with a 2 line pump to match the sender. Hope this helps jim __________________ 1984 K20 350M engine with 465,000 miles. Well, it's finally done!! Almost 2 years of work, but it was really worth the effort. Little stuff left to do is mount winch, wet sand & buff out and build belly pan\running boards. Body work takes lots and LOTS of beer!!!! God, Guts and Guns made America and God, Guts and Guns will preserve it! The worst thing you could do is get into my sights, but that don't matter, you'll never know it, cause you'll never hear the shotJim or Paladin whichever you choose.

03-06-2008, 01:53 AM	#3
streetmaster42 Registered User Join Date: Aug 2007 Location: Uniontown,PA Posts: 60	Re: Need info on a return line back to the fuel tank The stock pump that i got for my truck at AutoZone has 2 lines on it. I figured that one line went to the carb, and the other went to the tank. Theres also a 2 lines coming out of the sending unit, (1# 5/16)(2# 3/18) and the 5/16 line on the sending unit has a piece of hose with a bolt screwed into it.

03-06-2008, 02:57 AM	#4
James McClure One shot, one kill. Join Date: Dec 2007 Location: Saratoga Springs NY Posts: 859	Re: Need info on a return line back to the fuel tank streetmaster: OK, yours is matched correctly 2 for 2. Only problem is the line with the bolt in it. The bolt has to come out and have a vent end put in. The end to which I refer looks alot like the one for the rear end. If it's not there I'm not sure where you would get one, but your local Chevy store might be able to help you out. jim __________________ 1984 K20 350M engine with 465,000 miles. Well, it's finally done!! Almost 2 years of work, but it was really worth the effort. Little stuff left to do is mount winch, wet sand & buff out and build belly pan\running boards. Body work takes lots and LOTS of beer!!!! God, Guts and Guns made America and God, Guts and Guns will preserve it! The worst thing you could do is get into my sights, but that don't matter, you'll never know it, cause you'll never hear the shotJim or Paladin whichever you choose.

03-06-2008, 05:03 AM	#5
streetmaster42 Registered User Join Date: Aug 2007 Location: Uniontown,PA Posts: 60	Re: Need info on a return line back to the fuel tank Ok im starting to get whats going on with this emissions thing. Ill take that line with the hose on it, (Off) and run it back to the charcoal can, and be done with that. I now have to figure out if the PSV on my 350 splits off with one hose going to the char canister, and the other to the carb. Or if the PCV just goes to the carb. I know that the EGR goes to a TVS switch, but the hose from the TVS goes to the carb, aswell as the vacume advance, the mod valve for the TH350. The big problem im dealing with is, i have 1405 Edelbrock performer series carb that only has 2 small vacume port in the front of it. The one on the left is constant, and the one on the right is not. Do i (T) off the vacume advance with the hose from the TVS hose. Theres also the hose from the charcoal canister that goes to the carb, not sure if it needs to be hooked to a constant port or not. I guess what i need is a detailed list of how i can make all this work with the Edelbrock carb.



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