Seeking education on fuel pumps, gas caps, vapor canister - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**71CHEVYSHORTBED402** · 09-29-2016, 11:30 PM

71 c-10 402: I plan to install the charcoal canister with the rebuild. The aim is a stock set-up. A lot of questions, sorry about that. Appreciate any input.

1. Know which is the inlet from the tank to the fuel pump, #1 or #2 in the image?

2. I read one of these is a return line, "for cooling". Is that true? They also said this set-up requires a vented gas cap. Sounds like a vapor canister set-up, but what do I know.

3. I thought the other line was due to not having the vapor canister active. Is that a different line?

4. Did the original fuel pump have just one line from the tank?

5. With the canister installed, do you recommend I use a vented gas cap or not? Seems not, but.......

**71CHEVYSHORTBED402** · 09-30-2016, 12:13 PM

Ttt

**Boog** · 09-30-2016, 12:42 PM

The larger nipple is the inlet line. The smaller one is the return line to the tank. The tank will vent through a line that runs up in the right rear cab corner then down and to the charcoal canister under the hood Iirc.

**71CHEVYSHORTBED402** · 10-02-2016, 12:35 AM

Thanks Boog. Do you know if the return line was factory? I ask because I see pumps with just an inlet.

The two lines running up the cab has me stumped. Don't see it in the manual at the moment, but I'll know more after I pull the seat.

**Boog** · 10-02-2016, 12:17 PM

We all want to believe everything on our truck is as it came from OE but the truth is things can get changed over these 40 + years for whatever reason.
Here is a good view of the fuel and vent lines for these trucks from the LMC catalog.
http://www.lmctruck.com/icatalog/cb/full.aspx?Page=53

Yes the return line is OE beginning about 71.

**71CHEVYSHORTBED402** · 10-02-2016, 08:17 PM

Thanks again Boog. Here's a pretty good thread on this. http://67-72chevytrucks.com/vboard/s...d.php?t=526634

**71CHEVYSHORTBED402** · 10-07-2016, 10:11 PM

Pulled the bench seat and got under the truck. Unnecessary turns out, but I'm pulling everything anyway. There appears to be just two lines. My set up is the second pic. post 13 (SS strikes again) at http://67-72chevytrucks.com/vboard/s...d.php?t=526634

Unless there's a junction someplace, to me that means the original fuel pumps have one line connected to the tank. The other line runs from the tank straight to the vapor canister. Any confirmation appreciated.

**71CHEVYSHORTBED402** · 10-08-2016, 09:56 PM

Return line (5/16" ID) runs from gas tank to vapor canister. Original fuel pumps had one nipple, check?

Too obvious?

09-30-2016, 12:42 PM	#3
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,103	Re: Seeking education on fuel pumps, gas caps, vapor canister The larger nipple is the inlet line. The smaller one is the return line to the tank. The tank will vent through a line that runs up in the right rear cab corner then down and to the charcoal canister under the hood Iirc. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

10-02-2016, 12:35 AM	#4
71CHEVYSHORTBED402 Senior Member Join Date: Feb 2009 Location: Northern Nevada Posts: 7,189	Re: Seeking education on fuel pumps, gas caps, vapor canister Thanks Boog. Do you know if the return line was factory? I ask because I see pumps with just an inlet. The two lines running up the cab has me stumped. Don't see it in the manual at the moment, but I'll know more after I pull the seat. __________________ Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025

10-02-2016, 12:17 PM	#5
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,103	Re: Seeking education on fuel pumps, gas caps, vapor canister We all want to believe everything on our truck is as it came from OE but the truth is things can get changed over these 40 + years for whatever reason. Here is a good view of the fuel and vent lines for these trucks from the LMC catalog. http://www.lmctruck.com/icatalog/cb/full.aspx?Page=53 Yes the return line is OE beginning about 71. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

10-02-2016, 08:17 PM	#6
71CHEVYSHORTBED402 Senior Member Join Date: Feb 2009 Location: Northern Nevada Posts: 7,189	Re: Seeking education on fuel pumps, gas caps, vapor canister Thanks again Boog. Here's a pretty good thread on this. http://67-72chevytrucks.com/vboard/s...d.php?t=526634 __________________ Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025 Last edited by 71CHEVYSHORTBED402; 10-03-2016 at 12:00 AM.

10-07-2016, 10:11 PM	#7
71CHEVYSHORTBED402 Senior Member Join Date: Feb 2009 Location: Northern Nevada Posts: 7,189	Re: Seeking education on fuel pumps, gas caps, vapor canister Pulled the bench seat and got under the truck. Unnecessary turns out, but I'm pulling everything anyway. There appears to be just two lines. My set up is the second pic. post 13 (SS strikes again) at http://67-72chevytrucks.com/vboard/s...d.php?t=526634 Unless there's a junction someplace, to me that means the original fuel pumps have one line connected to the tank. The other line runs from the tank straight to the vapor canister. Any confirmation appreciated. __________________ Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025

09-29-2016, 11:30 PM	#1
71CHEVYSHORTBED402 Senior Member Join Date: Feb 2009 Location: Northern Nevada Posts: 7,189	Seeking education on fuel pumps, gas caps, vapor canister 71 c-10 402: I plan to install the charcoal canister with the rebuild. The aim is a stock set-up. A lot of questions, sorry about that. Appreciate any input. 1. Know which is the inlet from the tank to the fuel pump, #1 or #2 in the image? 2. I read one of these is a return line, "for cooling". Is that true? They also said this set-up requires a vented gas cap. Sounds like a vapor canister set-up, but what do I know. 3. I thought the other line was due to not having the vapor canister active. Is that a different line? 4. Did the original fuel pump have just one line from the tank? 5. With the canister installed, do you recommend I use a vented gas cap or not? Seems not, but....... __________________ Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025

09-30-2016, 12:13 PM	#2
71CHEVYSHORTBED402 Senior Member Join Date: Feb 2009 Location: Northern Nevada Posts: 7,189	Re: Seeking education on fuel pumps, gas caps, vapor canister Ttt __________________ Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025

10-08-2016, 09:56 PM	#8
71CHEVYSHORTBED402 Senior Member Join Date: Feb 2009 Location: Northern Nevada Posts: 7,189	Re: Seeking education on fuel pumps, gas caps, vapor canister Return line (5/16" ID) runs from gas tank to vapor canister. Original fuel pumps had one nipple, check? Too obvious? __________________ Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025



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