Dual tank/fuel gauge problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

USSkoval · 03-21-2010, 03:57 PM

I have another question about my '79 crew cab, this one involves the dual tanks and fuel gauge. It seems that the passenger side tank is the only one that works, but I really can't tell for sure. I do know that it is the one being used right now. Also, the gas gauge does not work at all. It was showing about 1/2 tank at all times before I removed the cluster.

Can a non-op valve cause the gas gauge not to work, or would it be the switch? Or maybe just the gauge is bad? I don't know how to test anything because the only diagram I can find shows a 4-wire switch. My switch in the dash has 5 wires... pink, pink/black, pink/white, light green, and light blue. The wires all appear to be OK.

kris's66lwb · 03-21-2010, 09:24 PM

i got the same problem any help for us guys?

Justins76 · 03-21-2010, 10:53 PM

When my selector solenoid goes bad it defaults to the RH tank.

USSkoval · 03-23-2010, 08:12 PM

Anymore help?

**old Rusty C10** · 03-23-2010, 08:20 PM

I popped out my dash switch on the 82 and then i checked the power on it when i switched it and i found my switch was bad. then i found that the valve at the bottom was bad ( prolly from years of not being used) but you should be able to test it with the test lite...i got my crossover valve on the bottom at auto zone as that was the cheapest the switch i got over the counter at advanced

USSkoval · 03-23-2010, 09:45 PM

I guess my biggest question is, will the gauge not operate at all if the switch and/or valve is bad? I have a good used switch and valve coming, when they get here I'll try the switch first, then the valve. I'm just wondering if there is simply a bad wire or two causing everything not to work.

3QTRTONS · 03-25-2010, 12:19 AM

I just replaced the Selector Valve on my 74 Super 20 - that was why my left tank was appearing to be 'empty' and 'inop', which it really wasn't.
BTW, the valve is a real 'treat' to replace.... with the bed on.
Overhead fuel line work / gotta hate it!

USSkoval · 03-25-2010, 12:30 AM

Just a small update for those that may be searching this topic in the future.

There is 5 terminals in the dash switch connector, I *think* I have them figured out as follows:
Blue- Sender signal from left side tank
Pink/White- Sender signal from right tank
Pink- Signal from switch to gauge
Pink/Black- Switched 12v power from ignition
Green- 12v power to valve (activates left tank)

The tank switching valve has a single wire hookup (green wire) and is self-grounding. This valve has nothing to do with the gauge readings. It seems that if it fails, you won't know it until you run out of gas.

In my case, the switch is working (I also had a blown fuse) and my fuel gauge is bad (needle spins around freely with no resistance at all). Hopefully tomorrow I can reinstall the gauge cluster with a fuel gauge from an '82 S-10, then see if my sending units operate correctly. I will also check out the valve, I'm suspecting either a bad wire or just a bad valve.

USSkoval · 03-25-2010, 12:32 AM

Quote:

Originally Posted by 3QTRTONS

I just replaced the Selector Valve on my 74 Super 20 - that was why my left tank was appearing to be 'empty' and 'inop', which it really wasn't.
BTW, the valve is a real 'treat' to replace.... with the bed on.
Overhead fuel line work / gotta hate it!

Does your valve also have the single wire that plugs into it?

3QTRTONS · 06-13-2010, 12:07 AM

SORRY, lost the thread til now....
Yes, I have the earlier 3 port style... 1 wire.

Did you end up taking care of the problem(s)???

USSkoval · 06-13-2010, 12:40 AM

Yes, most of the way. I had the blown fuse, bad gauge, and the harness unplugged at the firewall, so it wasn't hard to get working. The gauge does not read correct for the driver side tank and the rubber fuel hose leaks on that tank too. So I need to drop that tank and replace the sender and hoses... in the mean time, I'm just using that tank as a reserve.

Fixwhataintbroke · 06-14-2010, 12:14 PM

Just to add my two cents: The switch is easily rebuildable, just pop a couple tabs and clean the contacts, mine had 2 metal tabs, 2 springs, and 2 push pieces. Also, I discovered that you can switch between tanks about 6 times semi-fast and the gauge (for me at least) will kick in.

RootBreaker · 12-18-2017, 08:39 PM

I know a very OLD thread...
but I was googling for something else and found this...

so since I did an awesome job in MSPaint... years ago.. thought id add this for anyone else that is curious as I color coded including the switch...

03-21-2010, 03:57 PM	#1
USSkoval Registered User Join Date: Jul 2009 Location: West Jefferson, OH Posts: 999	Dual tank/fuel gauge problem I have another question about my '79 crew cab, this one involves the dual tanks and fuel gauge. It seems that the passenger side tank is the only one that works, but I really can't tell for sure. I do know that it is the one being used right now. Also, the gas gauge does not work at all. It was showing about 1/2 tank at all times before I removed the cluster. Can a non-op valve cause the gas gauge not to work, or would it be the switch? Or maybe just the gauge is bad? I don't know how to test anything because the only diagram I can find shows a 4-wire switch. My switch in the dash has 5 wires... pink, pink/black, pink/white, light green, and light blue. The wires all appear to be OK.

03-21-2010, 09:24 PM	#2
kris's66lwb resident wrencher Join Date: Dec 2006 Location: ramona california Posts: 720	Re: Dual tank/fuel gauge problem i got the same problem any help for us guys?

03-21-2010, 10:53 PM	#3
Justins76 OutOfMyMind & I'llNeverKnowWhy Join Date: Apr 2004 Location: Another world, some other time Posts: 672	Re: Dual tank/fuel gauge problem When my selector solenoid goes bad it defaults to the RH tank. __________________ -Justin-Out of my mind and I'll never know why 1976 Chevrolet Silverado C10 350 4bbl / TH350 Big10 longbed 1986 Pontiac Firebird T-Top 5.0L TPI 700R4 WS6 1992 Pontiac Firebird T-Top 5.0L TBI 700R4 My cardomain page I don't like to save, it's more fun to spend!!

03-23-2010, 08:12 PM	#4
USSkoval Registered User Join Date: Jul 2009 Location: West Jefferson, OH Posts: 999	Re: Dual tank/fuel gauge problem Anymore help?

03-23-2010, 08:20 PM	#5
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,268	Re: Dual tank/fuel gauge problem I popped out my dash switch on the 82 and then i checked the power on it when i switched it and i found my switch was bad. then i found that the valve at the bottom was bad ( prolly from years of not being used) but you should be able to test it with the test lite...i got my crossover valve on the bottom at auto zone as that was the cheapest the switch i got over the counter at advanced __________________ 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!!

03-23-2010, 09:45 PM	#6
USSkoval Registered User Join Date: Jul 2009 Location: West Jefferson, OH Posts: 999	Re: Dual tank/fuel gauge problem I guess my biggest question is, will the gauge not operate at all if the switch and/or valve is bad? I have a good used switch and valve coming, when they get here I'll try the switch first, then the valve. I'm just wondering if there is simply a bad wire or two causing everything not to work.

03-25-2010, 12:19 AM	#7
3QTRTONS Registered User Join Date: Mar 2010 Location: Warren, ME. Posts: 233	Re: Dual tank/fuel gauge problem I just replaced the Selector Valve on my 74 Super 20 - that was why my left tank was appearing to be 'empty' and 'inop', which it really wasn't. BTW, the valve is a real 'treat' to replace.... with the bed on. Overhead fuel line work / gotta hate it! __________________ 1994 C1500 rclb 1988 C1500 rclb 1969 ES5500 B E A S T 1983 C10 'farm truck' 1976 K20 Suburban 1984 K10 Suburban 1981 Jeep CJ5/350 Vortec 1941 Dodge WC18 Ambulance 2000 GMC Bus (parts warehouse)

03-25-2010, 12:30 AM	#8
USSkoval Registered User Join Date: Jul 2009 Location: West Jefferson, OH Posts: 999	Re: Dual tank/fuel gauge problem Just a small update for those that may be searching this topic in the future. There is 5 terminals in the dash switch connector, I think I have them figured out as follows: Blue- Sender signal from left side tank Pink/White- Sender signal from right tank Pink- Signal from switch to gauge Pink/Black- Switched 12v power from ignition Green- 12v power to valve (activates left tank) The tank switching valve has a single wire hookup (green wire) and is self-grounding. This valve has nothing to do with the gauge readings. It seems that if it fails, you won't know it until you run out of gas. In my case, the switch is working (I also had a blown fuse) and my fuel gauge is bad (needle spins around freely with no resistance at all). Hopefully tomorrow I can reinstall the gauge cluster with a fuel gauge from an '82 S-10, then see if my sending units operate correctly. I will also check out the valve, I'm suspecting either a bad wire or just a bad valve.

06-13-2010, 12:07 AM	#10
3QTRTONS Registered User Join Date: Mar 2010 Location: Warren, ME. Posts: 233	Re: Dual tank/fuel gauge problem SORRY, lost the thread til now.... Yes, I have the earlier 3 port style... 1 wire. Did you end up taking care of the problem(s)??? __________________ 1994 C1500 rclb 1988 C1500 rclb 1969 ES5500 B E A S T 1983 C10 'farm truck' 1976 K20 Suburban 1984 K10 Suburban 1981 Jeep CJ5/350 Vortec 1941 Dodge WC18 Ambulance 2000 GMC Bus (parts warehouse)

06-13-2010, 12:40 AM	#11
USSkoval Registered User Join Date: Jul 2009 Location: West Jefferson, OH Posts: 999	Re: Dual tank/fuel gauge problem Yes, most of the way. I had the blown fuse, bad gauge, and the harness unplugged at the firewall, so it wasn't hard to get working. The gauge does not read correct for the driver side tank and the rubber fuel hose leaks on that tank too. So I need to drop that tank and replace the sender and hoses... in the mean time, I'm just using that tank as a reserve. __________________ -Andy '77 K5 Blazer '78 K10 Shortbed '78 C20 Suburban '79 K30 Crew Cab Dually '84 C10 Short Stepside '88 K20 Suburban

06-14-2010, 12:14 PM	#12
Fixwhataintbroke Enthusiast Join Date: Jun 2010 Location: Graham, Wa. Posts: 192	Re: Dual tank/fuel gauge problem Just to add my two cents: The switch is easily rebuildable, just pop a couple tabs and clean the contacts, mine had 2 metal tabs, 2 springs, and 2 push pieces. Also, I discovered that you can switch between tanks about 6 times semi-fast and the gauge (for me at least) will kick in.

12-18-2017, 08:39 PM	#13
RootBreaker Registered User Join Date: Jun 2009 Location: Williamstown, NJ Posts: 10	Re: Dual tank/fuel gauge problem I know a very OLD thread... but I was googling for something else and found this... so since I did an awesome job in MSPaint... years ago.. thought id add this for anyone else that is curious as I color coded including the switch... __________________ Chrome dont get you home and looking at my truck is definite proof!!!! http://www.supermotors.net/users/RootBreaker



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