Duel Tanks SPILLING FUEL - The 1947 - Present Chevrolet & GMC Truck Message Board Network

WORNBRAKES · 03-09-2005, 10:33 PM

All,
I recently purchased a 76 K10 SWB pickup. I finally got the thing running but I have run into another problem and none of my books have the answer.

The truck has duel tanks. The right tank was empty and I filled up the left tank. After running the engine for a while, the right tank started spilling fuel out the top of the tank and the filler neck. The fuel is transfering into the right tank and is not stopping. My question is, is the selector valve bad or could it be plumed wrong? I can not find a diagram on how to plumb duel tanks. I can replace the valve but it has six ports and there are three hoses routed to it. That is why I suspect that they may be routed wrong.
Any help with this is greatly appreciated.
Thanks,
Mario

ElGracho · 03-09-2005, 10:59 PM

It sounds like they plumbed the return lines together with a tee rather than going through the tank valve. The fuel will take the path of least resistance and therefore return to the right tank (shorter path). There would be a few ways to fix this.

1) Don't use the left tank.
2) Get an older style fuel pump that doesn't have the return.
3) Fix it the right way and replumb the tank valve how it should be. The return lines (1/4") and the feed lines (3/8") should go to the valve from each sending unit. The 5/16" lines are the tank vent lines. My 1980 truck has two charcoal canisters so even the vent lines are not tee'd together.

WORNBRAKES · 03-10-2005, 12:12 PM

Thanks Joe
I seen a T when I was up there. I will take a look at it when I get home and try to get this thing fixed so I can start driving it.
Thanks again,
Mario

03-09-2005, 10:33 PM	#1
WORNBRAKES Senior Member Join Date: Jul 2001 Location: Hughesville, MD Posts: 1,350	Duel Tanks SPILLING FUEL All, I recently purchased a 76 K10 SWB pickup. I finally got the thing running but I have run into another problem and none of my books have the answer. The truck has duel tanks. The right tank was empty and I filled up the left tank. After running the engine for a while, the right tank started spilling fuel out the top of the tank and the filler neck. The fuel is transfering into the right tank and is not stopping. My question is, is the selector valve bad or could it be plumed wrong? I can not find a diagram on how to plumb duel tanks. I can replace the valve but it has six ports and there are three hoses routed to it. That is why I suspect that they may be routed wrong. Any help with this is greatly appreciated. Thanks, Mario __________________ Mario and Mandy Hughesville, MD 20637 69 C10 305/350 71 K5 Basket case 75 K10 Rescue Parting out 77 MG Midget Parting out 15 6.7L Cummins

03-09-2005, 10:59 PM	#2
ElGracho Gentleman Jim Driver Join Date: Nov 2002 Location: Poulsbo, WA Posts: 1,553	It sounds like they plumbed the return lines together with a tee rather than going through the tank valve. The fuel will take the path of least resistance and therefore return to the right tank (shorter path). There would be a few ways to fix this. 1) Don't use the left tank. 2) Get an older style fuel pump that doesn't have the return. 3) Fix it the right way and replumb the tank valve how it should be. The return lines (1/4") and the feed lines (3/8") should go to the valve from each sending unit. The 5/16" lines are the tank vent lines. My 1980 truck has two charcoal canisters so even the vent lines are not tee'd together. __________________ Joe '75 GMC Gentleman Jim '84 Chev C10 Short Wide - Super duper plain (manual steering, manual brakes, no dome light, no cig lighter) '85 Chev C10 Short Wide - Super plain Vortec 4.8 4L60E trans also: '81 K30, '83 C30 Crew Dually, '84 M1028 CUCV, '85 M1009 CUCV, another '85 C10 SWB, '89 R3500 Flatbed

03-10-2005, 12:12 PM	#3
WORNBRAKES Senior Member Join Date: Jul 2001 Location: Hughesville, MD Posts: 1,350	Thanks Joe I seen a T when I was up there. I will take a look at it when I get home and try to get this thing fixed so I can start driving it. Thanks again, Mario __________________ Mario and Mandy Hughesville, MD 20637 69 C10 305/350 71 K5 Basket case 75 K10 Rescue Parting out 77 MG Midget Parting out 15 6.7L Cummins

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