Trucks with Dual Saddle Tanks

[BigDave]

I am curious about this. I'm wondering if anyone has any information about this.

My 72 Cheyenne 402 BB has a seat tank and dual saddle tanks before each rear wheel. There is a tank selector on the floor between the driver's side rocker panel and the seat. It is very obvious it is not a factory option because the carpet is not stitched around the tank selector and there is no mention of this on the glovebox lid. The previous owner tells me it was a dealer installed option. He bought the truck in Midland, Texas.

The saddle tanks do not register on the fuel gauge. When the selector is set on one of them they pump into the seat tank via the return line as they are being used. They are fiberglass and the filler is under the wheel well. They hold about 21 gallons each. I've had around 64 gallons of gas on board at one time.

When I got the truck I had to re-run all the fuel lines because the saddle tank lines were trashed. All of the tank lines come into the selector and then one line goes to the fuel filter under the frame and forward to the fuel pump.

I can take pictures if you've never seen this before.

Any info would be helpful.

[mrein3]

Most of these setups are dealer installed. Some may have been added later by a previous owner. I have one on the drivers side of my truck.

I don't think they pump into the seat tank. I'm pretty sure when you select a tank it pumps (actually sucks) from each tank right to the engine.

My saddle tank did not have a fuel level sensor in it either. I bought a gauge and sender from JC Whitney. I drilled a second hole in the top of the tank for the sensor (the first hole being the tube the gas is sucked out of). I then mounted the gauge knee-knocker style under the dash.

My tank selector switch, mounted on the floor of the truck by the driver's door, has an extra position for another saddle tank. On my setup that extra "input" is simply blocked off.

[BigDave]

Thanks for your reply.

Only one extra tank?

My saddle tanks definately pump into the seat tank. At the time I would have never guessed it. However, I found out the hard way by running it over.

The thing I like about this the most is how I can place the selector in the forward position and cut off the fuel supply. Sometimes when I go out of town for a few days I'll put it in the forward position and then run it out of gas.

[Americanrider]

That was the common setup into the mid-late 70's. On my Dad's truck (a '75) it would fill the main tank and feed at the same time when running on the saddle. Funny to watch your dash gauge fill back up while driving on the saddle tank. No gauge or sender for the saddle, just a brass handle near the drivers rocker. Dealer never updated the glove box decal either.

[bouncytruck]

I have spare tanks in my Blazer. Word is they were manufactured by HICKEY and dealer installed. It is a very clean install so I believe it to be true. The tank selector is on the floor in front of the driver's seat. There are only two positions, one that draws from the factory tank and one from the spare tanks. The fuel gage only works for the factory tank.

[72 CustomCamper]

My 72 came factory with a single aux tank. It had a blazer style filler neck and the same type of selector valve by the seat. Mine also had a switch above the ac vent to switch sending units. The one's you have do sound like dealer add on or PO add on...


Chuck

[71Chevy4-speed]

Dual saddle tanks on mine, manual selector on the floor by the rocker panel, sucks straight to the motor, no gauge though..... like no sputtering either...just cruisin at 60...and whop.....dead...lol push the clutch and coast.

[ddsmith]

My saddle tanks are factory installed. The filler tubes come through the bed floor in both corners and out the bedsides up high at about the same level as the main tank gas cap. Mine also has the selector lever on the floor between the seat and the door. This one does not has provisions for fuel level on either of the aux tanks. I just shift when the gas runs out. The main tank level feeds the fuel gauge. I think maybe the reason your main tank fills up is because you have a return line on your setup. They normally did this in big block applications to prevent vapor lock problems. I think the small blocks did not have the return line. I could be wrong but I think it is the reason your main tank fills up when your aux tank is selected. You can tell by looking at the sending unit on the main tank. If you have two fuel lines then one is a return line and it is normally smaller diameter than the supply line.

[RainFade]

I have 2 saddle tanks on a factory 350, pretty sure they were dealer installed due to the ugly filler doors in the bed sides.

It doesn't have a return line just rubber line from the hard line on all 3 tanks to the switch by the driver rocker, one line out of that through an inline filter then to the hard line on the passenger side frame rail from there to the pump.

My saddle tanks were metal (were being past tense as they don't hold fuel too well when rusted out under the straps D'OH)
Sender is wired only to the main in-cab firebomb errr tank.

[4x4Poet]

Originally Posted by ddsmith

...I think maybe the reason your main tank fills up is because you have a return line on your setup. They normally did this in big block applications to prevent vapor lock problems. I think the small blocks did not have the return line. I could be wrong but I think it is the reason your main tank fills up when your aux tank is selected. You can tell by looking at the sending unit on the main tank. If you have two fuel lines then one is a return line and it is normally smaller diameter than the supply line.

I agree with this. Most likely. BigDave, besides checking for a return line system, a simple trace of the fuel lines underneath would also verify that none of the aux tank feed lines go anywhere near the main tank behind the seat. Obviously, when you have an aux tank or two full, you must run off the main tank first to get the fuel level down to 3/4 or 1/2, then run off each aux tank until you either empty them or see the main tank fuel gauge get too close to full, or should I say over-full.

Here's a thread with good saddle tank pics.
Saddle tanks out of the truck (off a shortbed).
Saddle tank care & repair

For safety's sake, the lines probably should be checked over their entire length for serviceability.

[BigDave]

Originally Posted by 4x4Poet

I agree with this. Most likely. BigDave, besides checking for a return line system, a simple trace of the fuel lines underneath would also verify that none of the aux tank feed lines go anywhere near the main tank behind the seat. Obviously, when you have an aux tank or two full, you must run off the main tank first to get the fuel level down to 3/4 or 1/2, then run off each aux tank until you either empty them or see the main tank fuel gauge get too close to full, or should I say over-full.

For safety's sake, the lines probably should be checked over their entire length for serviceability.

Correct, the reason why it siphons from the aux while they are in use is because of the return line on the BB402. All lines from every tank come into the selector and then out to the engine. You most definately cannot use them if the main tank is full.

Thanks for all of your comments guys.

[franko72]

I have 2 saddle tanks on my truck .One regular tank behind the seat, One saddle that was a factory install on the drivers side on underside of bed.the other saddle is a dealer install on the passenger side. It has the 3 way selector valve on the floor between the driver rocker panel and the seat, This part was a dealer add on.There is a factory switch that is mounted to the left of the guage cluster on the dash. It says (Aux. and Main )I have sending units in only the tank behind the seat and the passenger side saddle tank. The added saddle tank by the dealer doesnt have the sending unit.I only use one tank at a time.The option was listed on my glove box plate.

[Pilgrim]

I have twin 20 gallon metal saddle tanks in my 68 C20 suspended by two long bolts down through each tank with the fill through aluminum doors in each side of the bed. Appears to be a dealer installation. Selector valve by the drivers door on the floor. No gauges in either. Anyone have a source for level indicators for the aux. tanks? JCWhitney no longer has them in their catalogs. I presently run mine until they empty then switch.

[6869704X4]

My 70 had the saddles with the aluminum doors. All three had sending units. Valve setup like yall describe. Switch to the left of the instrument panel to swap the gas gauge to any tank.

[BLACK AND BLUE 67-72]

My 67 GMC has three tanks also the one behind the seat and two metal tanks under the sides of the bed, fillers for them are under the rear wheel wells it has a selector below the driver's side seat and a three way switch on the lower left side of the dash, the plate says aux, main, aux , when flipped to left the guage reads on the left side, when flipped to the right it reads on the right side, and when on main it reads like a normal guage. I have no idea if it is factory or dealer installed, it's a pretty cool setup though!!

[mrein3]

Originally Posted by BLACK AND BLUE 67-72

My 67 GMC has three tanks also the one behind the seat and two metal tanks under the sides of the bed, fillers for them are under the rear wheel wells it has a selector below the driver's side seat and a three way switch on the lower left side of the dash, the plate says aux, main, aux , when flipped to left the guage reads on the left side, when flipped to the right it reads on the right side, and when on main it reads like a normal guage. I have no idea if it is factory or dealer installed, it's a pretty cool setup though!!

I'm guessing the movement of gasoline in some folk's setups is just gas siphoning from one tank to the other. I guess there would be nothing wrong with that as long as one tank isn't lower than the rest - which would cause the lower tank to overflow and spill $1.88/gallon on the ground.

I haven't had time to look into it but I think the JC Whitney gauge/sender pictured above that I bought has the same resistance spec as the stock GM one. So in theory I could connect the wire from the resistor in the saddle tank to a switch to work with my factory gauge like others have from their dealer installed setup.

Tuck that trans temp gauge in the blank spot in my stock gauge bezel. Hook the back up lights as stock. Eliminate my knee-knocker setup. Hmmm....

[Misled]

Speaking of the in-cab tanks...

I know they are always referred to as fire-bombs and being dangerous, but does anyone know any true cases where there was a fire from a wreck or some other cause?

I can see the potential for problems, but I have never heard of any......

Thanks,

Misled

[Mudder]

I saw something a long time ago about our trucks on tv. It was showing how roll overs could cause the cap to be removed by hitting the pavement and gas coming out. Man that was a long time ago.

[mtdave2]

Well, my fist car, was a 72 c10. I ended up wrecking it into a pole. I slid into the pole an it impacted about mid door on the drivers side. once everything was over, I had a flame coming out of my gas filler pipe. The cap had been knock off and the gas (full tank thank god) caught fire.

As a side note, I also broke the pole, it almost fell on me. I cut thru most the power lines that were coming out of the ground going up the pole. Lastly I broke the steering wheel with my shoulder... lucky to live.

so, a direct impact did make it flame up!

[Misled]

mtdave2,
Thanks for the info........although I'm sure it wasn't personal knowledge that you WANTED to have!!!!!

What injuries did you receive?!?!

Misled

[mtdave2]

not a scratch! amazing huh. and my passenger wasnt wearing his seat belt. he was thrown forward and smacked his hip on the rear view mirror. again not a scratch..

[4x4Poet]

Looks like the Bitterroot Valley to me.