Sorry another fuel line question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Brettd85** · 11-12-2025, 08:23 PM

I’m doing a frame off on a 72 blazer and purchased the lines from inline tube. Where does the 1/4” return connect? Is it to the larger 5/16” vent line?? There isn’t a return on the sending unit. I looked at the assembly manual but maybe the wrong year!? Thanks in advance!

truckster · 11-12-2025, 10:29 PM

There's not a return on the stock 72 Blazer. I connected mine to the vent line.

hemi43 · 11-13-2025, 10:26 AM

The fuel line kit might have included a return 1/4" line for those that install an aftermarket fuel injection system.

**1970cstblazer** · 11-13-2025, 11:25 AM

1972 Series 10-30 350 with Turbo Hydramatic transmission called for AC brand fuel pump 40867, which had a 1/4" return nipple per the GM parts manual.

**DeadheadNM** · 11-13-2025, 01:23 PM

Quote:

Originally Posted by 1970cstblazer

1972 Series 10-30 350 with Turbo Hydramatic transmission called for AC brand fuel pump 40867, which had a 1/4" return nipple per the GM parts manual.

This a photo from eBay and the seller may be mistaken. Another seller has the same p/n for a pump that lacks a return line. My 72's didn't have any fuel return line, just the vapor line iirc: https://67-72chevytrucks.com/vboard/...0&postcount=34

InLine Tube is famous for making mistakes

**1970cstblazer** · 11-13-2025, 02:43 PM

Quote:

Originally Posted by DeadheadNM

This a photo from eBay and the seller may be mistaken. Another seller has the same p/n for a pump that lacks a return line. My 72's didn't have any fuel return line, just the vapor line iirc: https://67-72chevytrucks.com/vboard/...0&postcount=34

InLine Tube is famous for making mistakes

Agree on ILT.

Here is the excerpt from the partsbook. Obviously, these have been wrong in the past and can't be considered gospel.

**Brettd85** · 11-13-2025, 07:54 PM

Hmm. Thanks for help so far. All the verbiage online says this 1/4” line replaces the factory one. So consensus is there shouldn’t be a return??

Where does the vent tube that goes forward connect to? I assume the charcoal canister but I can't find a hardline reproduced for that?

hemi43 · 11-13-2025, 09:13 PM

FWIW, that 1/4 "vent" return might be to prevent vapor lock. I know Mopars had these on their high performance engines, but they had it on the fuel filter.
This was used to send fuel vapor back to the tank in case the fuel boiled in the lines due to high temperatures. Maybe this was GM's fix.
My Blazer is a 1970 so I never encountered this.

https://www.moparts.ca/oer-1968-71-d...-426-440-mf282

**Brettd85** · 11-21-2025, 09:35 PM

I’m still having trouble getting confirmation on the 1/4” return and also if there is a hardline for the vent tube to run forward to a charcoal canister? Anyone?

maldo · 03-26-2026, 10:27 PM

I hope this help, I do not see a 1/4 return line in images.

11-12-2025, 08:23 PM	#1
Brettd85 Active Member Join Date: Jan 2011 Location: Redmond, WA Posts: 107	Sorry another fuel line question I’m doing a frame off on a 72 blazer and purchased the lines from inline tube. Where does the 1/4” return connect? Is it to the larger 5/16” vent line?? There isn’t a return on the sending unit. I looked at the assembly manual but maybe the wrong year!? Thanks in advance! Attached Images

11-12-2025, 10:29 PM	#2
truckster Registered User Join Date: Jan 2001 Location: Orem, Utah Posts: 8,264	Re: Sorry another fuel line question There's not a return on the stock 72 Blazer. I connected mine to the vent line. __________________ I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man. - Thomas Jefferson 1972 K/5 Blazer CST 4WD 1963 Corvair Monza Spyder Turbo convertible 1995 Camaro Z/28

11-13-2025, 10:26 AM	#3
hemi43 Registered User Join Date: Mar 2015 Location: Ontario Canada Posts: 1,612	Re: Sorry another fuel line question The fuel line kit might have included a return 1/4" line for those that install an aftermarket fuel injection system.

11-13-2025, 11:25 AM	#4
1970cstblazer All stock and staying that way Join Date: Jul 2003 Location: Elkland, PA Posts: 2,500	Re: Sorry another fuel line question 1972 Series 10-30 350 with Turbo Hydramatic transmission called for AC brand fuel pump 40867, which had a 1/4" return nipple per the GM parts manual. __________________ 1970 K/5 Blazer CST 4WD, TOTM winner December 2024! Medium Bronze poly, 93k ACT. miles, 350, 4 speed, rear positraction, 16.5" x 8.25" HD Kelsey Hayes wheel option, tilt, tach, vacuum, AM/FM, manual throttle...Dad ordered and purchased new 4/70. Frame off restored 1970 K20, To be a clone of my Grandfather's K20, Dark Blue poly, 350, 4 speed, 16.5" X 8.25" Kelsey Hayes wheel option, tilt, tach, vacuum, AM radio. Latest project truck 1972 Cheyenne Super 20 2WD, Dark Blue/White, 90K ACT. miles, 402, TH400, 4.10 open, tilt, tach, vacuum, A/C, AM/FM, manual throttle.. A mostly original paint never rusted Texas survivor... 2017 Sierra 1500 SLT 4WD, Black, 51k miles, 5.3, 6L80E, 3.42 LS, 20" polished wheels, everything but moonroof and 6.2... 2019 Canyon SLT 4WD, White, 71k miles, 3.6, 8L45, 3.23 LS, 18" wheels

11-13-2025, 07:54 PM	#7
Brettd85 Active Member Join Date: Jan 2011 Location: Redmond, WA Posts: 107	Re: Sorry another fuel line question Hmm. Thanks for help so far. All the verbiage online says this 1/4” line replaces the factory one. So consensus is there shouldn’t be a return?? Where does the vent tube that goes forward connect to? I assume the charcoal canister but I can't find a hardline reproduced for that?

11-13-2025, 09:13 PM	#8
hemi43 Registered User Join Date: Mar 2015 Location: Ontario Canada Posts: 1,612	Re: Sorry another fuel line question FWIW, that 1/4 "vent" return might be to prevent vapor lock. I know Mopars had these on their high performance engines, but they had it on the fuel filter. This was used to send fuel vapor back to the tank in case the fuel boiled in the lines due to high temperatures. Maybe this was GM's fix. My Blazer is a 1970 so I never encountered this. https://www.moparts.ca/oer-1968-71-d...-426-440-mf282

11-21-2025, 09:35 PM	#9
Brettd85 Active Member Join Date: Jan 2011 Location: Redmond, WA Posts: 107	Re: Sorry another fuel line question I’m still having trouble getting confirmation on the 1/4” return and also if there is a hardline for the vent tube to run forward to a charcoal canister? Anyone? Last edited by Brettd85; 11-23-2025 at 03:22 PM.

03-26-2026, 10:27 PM	#10
maldo Registered User Join Date: Nov 2015 Location: cali Posts: 768	Re: Sorry another fuel line question I hope this help, I do not see a 1/4 return line in images. Attached Images



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