fuel line identification on dual tank system - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Earl Filter · 05-21-2005, 10:16 PM

I took the passenger side tank off my '77 C20 and cleaned it up. This is a dual tank truck, but only the passenger side is hooked up (I got it that way). Off of the fuel sender/pickup on top of the tank there were 3 lines:

The big, fat fuel line to feed the 454
The middle one was about 3 inches long, and had a plug/vent thingy on the end
The third is the smallest of the 3, and went to a hard metal line on the frame that went up to the front of the vehicle.

I couldn't trace the third line, as it was getting dark, but it went up to about the right front control arm area, then went somewhere I couldn't see. What is that line?

79BIG10 · 05-21-2005, 10:54 PM

The third line is a return line from the fuel pump. It bleeds off any excess the pump doesn't sent to the carb.

Earl Filter · 05-22-2005, 12:32 AM

I guess it's been a long time since I've messed with a mechanical fuel pump setup...I didn't realize they had a return. Thanks!

plumbcut · 05-22-2005, 03:32 AM

im pretty sure that only heavy duty and/or AC trucks had the 3rd (return) line for that year....got any pics of the truck? where are you from?

Earl Filter · 05-22-2005, 10:09 AM

Quote:

Originally Posted by plumbcut

im pretty sure that only heavy duty and/or AC trucks had the 3rd (return) line for that year....got any pics of the truck? where are you from?

I just bought the truck from a friend of a friend for $300. It is a C20 3/4 ton, and does have factory A/C. The boxes and compressor mounted in the bed have been there almost since day one. The guy I bought it from bought it from the company he worked for at the time after it did 2 years of service work. He was the driver from new. I'm just west of the Houston, Tx area. Here's a pic of the truck, and one of the SPID sheet:

05-21-2005, 10:16 PM	#1
Earl Filter Registered User Join Date: May 2005 Posts: 212	fuel line identification on dual tank system I took the passenger side tank off my '77 C20 and cleaned it up. This is a dual tank truck, but only the passenger side is hooked up (I got it that way). Off of the fuel sender/pickup on top of the tank there were 3 lines: The big, fat fuel line to feed the 454 The middle one was about 3 inches long, and had a plug/vent thingy on the end The third is the smallest of the 3, and went to a hard metal line on the frame that went up to the front of the vehicle. I couldn't trace the third line, as it was getting dark, but it went up to about the right front control arm area, then went somewhere I couldn't see. What is that line? __________________ Real Name - Brandon Current Vehicles: 1977 C20 Silverado 454/TH400 3.73s 1989 Jaguar XJ6 in the middle of an LT1/4L60E swap

05-21-2005, 10:54 PM	#2
79BIG10 I'm back with 2nd truck! Join Date: Feb 2002 Location: Texas Posts: 3,774	The third line is a return line from the fuel pump. It bleeds off any excess the pump doesn't sent to the carb. __________________ 1979 Chevrolet Bonanza Big10 "Tootsie Roll" 1985 Chevrolet Silverado (wife's) Member of the Southern Bowties Club "Don't underestimate how sexy a fat man who drinks to excess can be." Homer Simpson

05-22-2005, 12:32 AM	#3
Earl Filter Registered User Join Date: May 2005 Posts: 212	I guess it's been a long time since I've messed with a mechanical fuel pump setup...I didn't realize they had a return. Thanks! __________________ Real Name - Brandon Current Vehicles: 1977 C20 Silverado 454/TH400 3.73s 1989 Jaguar XJ6 in the middle of an LT1/4L60E swap

05-22-2005, 03:32 AM	#4
plumbcut california fill Join Date: Apr 2004 Location: Sunny So-Cal Posts: 694	im pretty sure that only heavy duty and/or AC trucks had the 3rd (return) line for that year....got any pics of the truck? where are you from?



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