Gas Tank Sending Unit Help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

BrookelynnGreen · 01-13-2012, 10:46 PM

I have a truck with dual gas tank setup. I currently use my right tank. And I looked today and I have no left side gas tank. If I buy a left side tank from a salvage can I just install it?
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BrookelynnGreen · 01-14-2012, 06:54 AM

My 86 has a dual tank setup, and its missing the left side gas tank. I got under the truck to see what all I needed and I saw 3 metal fuel lines that probably connect to a 3 hole sending unit. Why does it have 3 holes?? Can someone tell me? I don't know anything about this, and I want to put a new tank in there but I need to know if I have to buy a 3 hole sending unit since the truck has 3 fuel lines that lead to the left side. My right side works like a charm fyi.
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**old Rusty C10** · 01-14-2012, 09:45 AM

one line goes to the fuel pump one line is to the charcoal cannister and the other line is either an overflow or vent tube.. mine had the same exact thing

BrookelynnGreen · 01-14-2012, 09:47 AM

Do I need a left side gas tank with a 3 hole sending unit? Anyone know?
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Prong · 01-14-2012, 04:46 PM

To do it right, you need the 3 line unit. The connections are as follows: 3/8" is fuel feed, the 5/16" is vapor line, and the 1/4" is for fuel return line. You have a 6 port switching valve, correct?

BrookelynnGreen · 01-14-2012, 04:48 PM

What is a 6port valve switch?
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bmchevy1979 · 01-15-2012, 11:29 AM

He is talking about the tank selector valve on the right side frame rail

wilkin250r · 01-15-2012, 01:58 PM

I just pulled my gas tank and had to diagnose problems this last summer. The components are fairly simple, you just need to make sure you have all of them.

In the cab, there is the tank selector switch and associated wiring.

Under the truck, you obviously already have the fuel lines from the tank, you just need to make sure they are the same as the tank you are getting. If you have three lines, like Prong said above, the largest is the main fuel line, the second is the vent line (also called the vapor line) and the smallest is the fuel return line.

Near the fuel tanks, attached to the frame rail under the truck, there is a fuel selector valve. It should look something like this, and there are a couple different wiring configurations. It's the item that actually routes the fuel from whichever tank you have selected.

And then the obvious, you'll have to make sure everything is connected properly and in working order. Let's start with finding the components, and then we'll move on to testing them.

01-13-2012, 10:46 PM	#1
BrookelynnGreen Registered User Join Date: Sep 2011 Location: Albany, New York Posts: 125	Fuel tank help I have a truck with dual gas tank setup. I currently use my right tank. And I looked today and I have no left side gas tank. If I buy a left side tank from a salvage can I just install it? Posted via Mobile Device __________________ -Samuel "Knowledge Is Power"

01-14-2012, 06:54 AM	#2
BrookelynnGreen Registered User Join Date: Sep 2011 Location: Albany, New York Posts: 125	Gas Tank Sending Unit Help My 86 has a dual tank setup, and its missing the left side gas tank. I got under the truck to see what all I needed and I saw 3 metal fuel lines that probably connect to a 3 hole sending unit. Why does it have 3 holes?? Can someone tell me? I don't know anything about this, and I want to put a new tank in there but I need to know if I have to buy a 3 hole sending unit since the truck has 3 fuel lines that lead to the left side. My right side works like a charm fyi. Posted via Mobile Device __________________ -Samuel "Knowledge Is Power"

01-14-2012, 09:45 AM	#3
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,313	Re: Gas Tank Sending Unit Help one line goes to the fuel pump one line is to the charcoal cannister and the other line is either an overflow or vent tube.. mine had the same exact thing __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

01-14-2012, 09:47 AM	#4
BrookelynnGreen Registered User Join Date: Sep 2011 Location: Albany, New York Posts: 125	Re: Gas Tank Sending Unit Help Do I need a left side gas tank with a 3 hole sending unit? Anyone know? Posted via Mobile Device __________________ -Samuel "Knowledge Is Power"

01-14-2012, 04:46 PM	#5
Prong Registered User Join Date: May 2007 Location: CO Posts: 475	Re: Gas Tank Sending Unit Help To do it right, you need the 3 line unit. The connections are as follows: 3/8" is fuel feed, the 5/16" is vapor line, and the 1/4" is for fuel return line. You have a 6 port switching valve, correct?

01-14-2012, 04:48 PM	#6
BrookelynnGreen Registered User Join Date: Sep 2011 Location: Albany, New York Posts: 125	Re: Gas Tank Sending Unit Help What is a 6port valve switch? Posted via Mobile Device __________________ -Samuel "Knowledge Is Power"

01-15-2012, 11:29 AM	#7
bmchevy1979 Registered User Join Date: Dec 2010 Location: Visalia, Ca Posts: 707	Re: Gas Tank Sending Unit Help He is talking about the tank selector valve on the right side frame rail __________________ <Brandon> 1974 Chevrolet K5 Blazer 350sbc/SM465/NP205, dana44 front, corp 14bolt rear with 4.10s and a powertrax locker, custom rear bumper 400sbc in the works. 1981 GMC C1500 stepside 250i6, 3spd, 12bolt with 3.08s 2.5/4drop on 15x10 with 275/50r15 81 GMC C3500 cab-chassis dually with utility bed 350sbc, Sm465, 14bolt with 4.10s nv4500 getting ready to go in 1979 Chevrolet K5 R.I.P. http://67-72chevytrucks.com/vboard/s...d.php?t=434096 1976 Chevrolet C10 R.I.P. http://67-72chevytrucks.com/vboard/s...d.php?t=434195

01-15-2012, 01:58 PM	#8
wilkin250r Registered User Join Date: Sep 2010 Location: Lake Tahoe, Nevada Posts: 755	Re: Gas Tank Sending Unit Help I just pulled my gas tank and had to diagnose problems this last summer. The components are fairly simple, you just need to make sure you have all of them. In the cab, there is the tank selector switch and associated wiring. Under the truck, you obviously already have the fuel lines from the tank, you just need to make sure they are the same as the tank you are getting. If you have three lines, like Prong said above, the largest is the main fuel line, the second is the vent line (also called the vapor line) and the smallest is the fuel return line. Near the fuel tanks, attached to the frame rail under the truck, there is a fuel selector valve. It should look something like this, and there are a couple different wiring configurations. It's the item that actually routes the fuel from whichever tank you have selected. And then the obvious, you'll have to make sure everything is connected properly and in working order. Let's start with finding the components, and then we'll move on to testing them.



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