Adding a Second Tank to an Original Dual Tank Truck

[hambo]

Hey GM Squarebody,

I'm looking to add a second tank to my truck. It originally was a dual tank truck but the old drivers side tank rusted out so the previous owner just took it out. Now my passenger tank is leaking so I figured I'd replace both tanks so I can have two again.

I found a dual tank truck being parted out and I was wondering what parts I need to run duel tanks again? Under my truck I see a two way valve with one side going to my current tank. I also have the switch on my dash and when I switch it to the drivers tank that isn't there, the fuel cuts off and the truck dies. So the switch and valve I think are working.

What do I need from the parts truck besides the 2nd tank and sending unit? And how are the lines routed for duals? I read that the return and vent lines are possibly split to both tanks? And does the dual tank use a different sending unit that just a normal single tank?

My truck is an 87 TBI 454.

Thanks!


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[crazy4offroad]

The sending units are unique to each side, and the mounting brackets are unique. You'll also need the transfer valve and dash switch, and if you can, get the pigtail for the switch if yours is gone. You may want to pick up a roll of nylon fuel hose, rubber is disintegrating these days with all the ethanol that's in gas. I think there's a metal line that goes across a crossmember at the back of the cab for the driver side tank to feed over to the transfer valve. You don't really need it but if it's in good shape pick it up, otherwise just use nylon hose and tie it up. You may also want to check on the charcoal canisters, there should be one on each side. There's a metal line on each side that vents to the charcoal canisters hopefully yours are still in place and not plugged.

 

[hambo]

The sending units are unique to each side, and the mounting brackets are unique. You'll also need the transfer valve and dash switch, and if you can, get the pigtail for the switch if yours is gone. You may want to pick up a roll of nylon fuel hose, rubber is disintegrating these days with all the ethanol that's in gas. I think there's a metal line that goes across a crossmember at the back of the cab for the driver side tank to feed over to the transfer valve. You don't really need it but if it's in good shape pick it up, otherwise just use nylon hose and tie it up. You may also want to check on the charcoal canisters, there should be one on each side. There's a metal line on each side that vents to the charcoal canisters hopefully yours are still in place and not plugged.

Thanks for the info. Would you know where to find like a full diagram of the dual tank system? And could I use the sending units that are currently in the tanks on the parts truck even though its an 85 so its carburetor? And where exactly are the charcoal canisters? The side of the tanks?

 

[crazy4offroad]

The charcoal canisters are under the hood. The sending units should work ok, granted they aren't rusted or the screen "sock" in the tank isn't gummed up. I think most Haynes manuals should have a fuel system diagram. My manual is in pretty bad shape, and I think they frown on posting images of copyrighted material on here. I think the year break is early 80s where the transfer valve changed from 3-port to I think 5- or 6-port. Basically anything with TBI should have a fuel return line, and that's what the 2 extra ports are for.

 

[74propu]

no the tanks out of the 85 will not work the tbi needs to fuel pump in the tank where the 85 had a carb and the pump on the engine look and see if the crossover lines are still on the frame under the cab at the crossmember and see if thay are still hooked to the fuel valve if they are look on rock auto for a new tank thay are like $86 for a 20 gal with baffle and the pump sending unit is around $90 . but the tank brackets from the 85 will work on your 87 I am adding a 2nd tank to my 86 and elec fuel pumps for my 454 tbi all new tanks and pump/senders so I feel your pain you just need 1 tank I need 2 of everything

 

[hambo]

no the tanks out of the 85 will not work the tbi needs to fuel pump in the tank where the 85 had a carb and the pump on the engine look and see if the crossover lines are still on the frame under the cab at the crossmember and see if thay are still hooked to the fuel valve if they are look on rock auto for a new tank thay are like $86 for a 20 gal with baffle and the pump sending unit is around $90 . but the tank brackets from the 85 will work on your 87 I am adding a 2nd tank to my 86 and elec fuel pumps for my 454 tbi all new tanks and pump/senders so I feel your pain you just need 1 tank I need 2 of everything

Okay. So even the 85 tanks won't work?? How are they different than the 87? Because of the sending unit/internal pump on the 87 is the sending unit hole different on the 85 tank vs the 87?

 

[74propu]

Okay. So even the 85 tanks won't work?? How are they different than the 87? Because of the sending unit/internal pump on the 87 is the sending unit hole different on the 85 tank vs the 87?

inside the 87 tank there is a sump that the fuel pump sits in so it doesn't lose presser when the tank is about empty when brakeing and tacking off from a stop . it is called a baffle other then that the tanks are the same

 

[hambo]

Okay thanks for the info. I'll order an 87 tank. Should I order news straps while I'm at it as well? Do they tend to snap when removing?


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[chengny]

Here are the parts dwgs and numbers lists for your application - an 87 V2 -30 with dual tanks and a TBI 454 (L19).

Fill pipes & vents :

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Tanks and mounting:

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Rear section of fuel and vent piping:

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Forward section of fuel system:

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TBI related components:

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ECM/TBI harness layout:

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Air intake system:

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Evaporative emissions components:

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EGR and venting:

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Accelerator linkage and mounting:

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Smog pumps and piping:

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Exhaust system heat shields:

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I tried for quite awhile to locate the correct exhaust system dwg for your truck, but couldn't find your exact combination of body style (03), GVWR code (2), engine size/model (L19) and drive train type (V). BTW - 1986 was the last year the K designation was used, after that 4WD models switched to the V code. And C trucks became R trucks.

Anyway, I bet someone somewhere along the line, dropped in a L19 454. But the L19 code isn't the problem, I also checked all the exhaust systems that were matched to the LE8 454 - still nothing. It doesn't appear that the 454 engine was available in a 4WD 3/4 ton standard pickup truck in 1987. There are all kinds of dwgs showing the exhaust systems of 1 ton trucks with 454's, there are even a few for 2WD 3/4 ton trucks with the 454. Also if you drop down to 1986, there are several versions of 3/4 ton 4WD trucks with 454's , but they appeared to have ended with the K designation.

 

[bucket]

There were no 3/4 ton 4x4 trucks with a big block until the GMT400 body style. Even the '77-'80 K30's were smallblock only.

Also, the tank brackets have all the holes in them to be used on either side of the truck. The only difference is where the nuts are welded on. So you can weld nuts onto the blank holes, or just hold a wrench up in there when you put them on.