Auxiliary fuel tank in my LX450 (1 Viewer)

[86tuning]

Auxiliary fuel tank build in 2016
Installed in 1997 LX450

Cliff notes:
S10 blazer 20gal (76L) fuel tank. Home built fuel pump controller and dual filler neck.

S10/S15 blazer tank fits fine and doesn't hang lower than the spare did when it lived under there. The filler neck for the tank is in a good spot, pointing to the left side of the truck. The fuel pump outlet then points forwards.

Shown above, new aftermarket Chevy Blazer fuel tank with internal EFI fuel pump. White thing is the flow switch that will allow me to interrupt power to the transfer pump when no fuel is flowing. On the left is a 12v timer that I ended up not using, along with the SUB switch and a random waterproof connector I'm using for the fuel pump and the flow switch. Blue hose is push-loc hose that's used on budget racecars and other industrial applications. Rated 250psi, fuel safe, oil safe, etc.

Useable capacity of the 76L tank is actually 80L when pumped dry. So in effect I've doubled the range of the truck.

Brackets installed to hang fuel tank using blazer tank mount straps.

The most difficult part of this build was creating the filler neck. Although I could have used the Toyota filler neck, I wanted a simple system without any knobs or levers. With my siamese filler neck, the main tank fills normally. No pre-flight instructions required for any crew members borrowing and filling the truck. Just don't put diesel in there. To fill the auxiliary tank, the nozzle is pointed back towards the aux fill neck, and I can feel when it engages the tube. I can therefore fill either tank, and the 'hidden' auxiliary tank fill isn't an issue for anyone else.

However, some fuel station nozzles have a stopper ring below the spring, and won't allow easy filling of the auxiliary tank. Also, I haven't been to California yet, so don't know if a vapour recovery nozzle will reach the aux tank filler either. The main tank filler is unchanged so there's no issues ever filling the main tank.

This pic shows the preliminary fitting stage. Not shown is the TIG welding, leak testing, brazing to fix the leaks, and the 3/8" inlet pipe to allow fuel transfer from the auxiliary fuel tank pump.

 

[86tuning]

Fuel pump controller on the breadboard.

There's a timer to start the pump and run it for 30s to initialize fuel transfer. There's an input from the main fuel tank level gauge to halt fuel transfer when main tank is 9/10 full. There's an input from a flow switch to interrupt transfer when the transfer pump stops pumping fuel (and tries to push air).

Assembled on a prototype board. Powered using a defog switch that's been re-labelled SUB. Thanks Joey Romero for the switch labels.

The final circuit, deadbug style built on a BOSCH automotive 12v relay. It's tucked in the center console behind the SUB switch.

 

[86tuning]

After I built the discrete fuel pump controller, my brother (a computer geek) asks me why I didn't install a programmable microcontroller. He explained to me how much more robust the microcontrollers are than discrete componentry, and allow easy it is to make firmware changes. Plus multiple inputs and and outputs for monitoring. Microcontrollers are used everywhere and rarely fail. The keypad on a microwave oven, for example, has a microcontroller driving it. When's the last time a microwave oven died because of keypad/microcontroller failure?

I figure discrete componentry is plenty robust. My controller has a single monitor output, to illuminate the SUB switch lamp when the pump is running. That's all. Two inputs, one from the fuel level sender, and one from the pump flow switch. I eliminated the potentiometer in the prototype and replaced it with separate resistors which are both cheaper, and non-adjustable, so it cannot be knocked out of adjustment. 555 timer chips don't die, and voltage comparitors are pretty stable too. It's been a long time since high school electronics, but I can still sorta solder ok. And deadbug circuits are so steampunk. lol.

Stock EFI in-tank fuel pump in the S10/S15 puts down about 30gph. So to transfer 20gal it takes about 40 mins. That said, I usually transfer fuel when the main tank is about 1/2 because the vehicle handles better with the fuel load forward between the axles instead of behind the rear axle. On smooth roads, there's more fuel transfer than on bumpy or twisty roads. Whenever the fuel level sender goes above 9/10 the transfer pump will stop. Even if it's from fuel slosh. So my system isn't perfect, but works well enough.

Also, GM fuel pumps don't seem to last a long time, but if it lasts 50,000miles of continuous use in a GM truck, it should last for the life of my vehicle in my application, because it only runs for 20 minutes at a time. Although I do run it dry regularly which isn't good for the life of the pump either.

 

[Malleus]

I like it! What was the total build cost?

 

[I Lean]

What year was that tank intended for? I ask because I just put an S10 Blazer tank under mine, and it came with a completely different bracket system. (larger brackets underneath, straps on top...mine was a 1995)

 

[Mdej3]

Great job sir!!

 

[alia176]

agreed, great job.

 

[86tuning]

I like it! What was the total build cost?

Filler neck took two tries. I had purchased a spare upper neck from a 'mud member that put a dual neck in theirs, so I modified it. Then ripped it out, and modified the original filler that came out of mine. So a whole whack of time to do the filler neck. Didn't work properly until the second try. Would've been cheaper to buy a used toyota dual neck and put it in. But what's the fun in that? Only other thing I would do differently with the filler neck is to add a second air return fitting and do separate air returns so that I can fill faster. Because the gas station nozzle shuts off when it touches fluid, and the air return pipe, if it has fuel in it from the other tank, will slow down filling.

Tank was cheap, about $2-300 including the pump and hangers. I forget (conveniently, especially when wife asks) how much it actually cost.

I probably spent $150 doing the pump controller. I hadn't done any electronics stuff for decades, so it was fun getting into it again. 10/10 would do again. Already had the soldering iron and soldapullit desoldering tool. Also had the breadboards and stuff laying around too.

Flow switch may have been sourced through amazon.com or similar online supplier.

What year was that tank intended for? I ask because I just put an S10 Blazer tank under mine, and it came with a completely different bracket system. (larger brackets underneath, straps on top...mine was a 1995)

Can't remember offhand I bought the tank about 2 years ago. It's the 76L S10/S15 tank. My local parts store supplied a tank. Can't remember the actual brand. Probably Spectra. The EFI pump with bracket was the same brand.
edit: looking at the pics, it appears that the tank is designed with different brackets. My upper brackets are made of 1/8" thick steel, and we just looped the straps underneath like any other Toyota. So we are probably using the same unit. Only mine is slapped in differently.

Great job sir!!

Thanks!

agreed, great job.

Thanks!

Now I wish I had an auxiliary wallet to go with the fuel tanks. Gas is about C$1.30/L which is right around US$4/gal up here in Vancouver.

 

[Rifleman]

I like your build, the only item I would add would be some strips of rubber between the tank, and it's mounting brackets. I've always been a safety nut, so I'm not a big fan of metal, rubbing against metal, on a fuel tank. YMMV

 

[alia176]

In case others come to this thread and don't have the ability/fortitude to make their own transfer ECUs, we have a Mud member who makes a very nice fuel transfer ECU on a tiny PCB. It lights up the Sub tank light while running the aux pump and then shuts off the aux pump when the empty signal gets activated from the aux fuel tank empty indicator. I've been using it for 14 years now. Anyway, just a FYI.

 

[86tuning]

In case others come to this thread and don't have the ability/fortitude to make their own transfer ECUs, we have a Mud member who makes a very nice fuel transfer ECU on a tiny PCB. It lights up the Sub tank light while running the aux pump and then shuts off the aux pump when the empty signal gets activated from the aux fuel tank empty indicator. I've been using it for 14 years now. Anyway, just a FYI.

Yes! I read about George's auxiliary fuel tank ecu, and that's what inspired me to make my own. And I am in debt to every single writeup of auxiliary fuel tanks on this forum. Without the forum, and all the pictures and writeups for inspiration, not much would have ever gotten done on my truck.

However, all that said, you guys are generally a bunch of bad influences. I'm trying to stay away from all the supercharger talk, and the re-gearing of the transfer case threads.

Cheers, to all the mudders out there that made me feel the need for an auxiliary fuel tank, when plain old NATO gas cans are functional and somewhat easily acquired.

 

[Rifleman]

In case others come to this thread and don't have the ability/fortitude to make their own transfer ECUs, we have a Mud member who makes a very nice fuel transfer ECU on a tiny PCB. It lights up the Sub tank light while running the aux pump and then shuts off the aux pump when the empty signal gets activated from the aux fuel tank empty indicator. I've been using it for 14 years now. Anyway, just a FYI.

Is this a photo of what your talking about?
Here's a link to the print.
PDF schematic.
Link to George's web site.
George's 80 Series Land Cruiser and Nissan MQ Patrol

 

[JaketheSSnake]

What year blazer is the tank from?

 

[I Lean]

What year blazer is the tank from?

Mine looks the same as his, and was from a 1995. I think 87-95 is the range for that style.

 

[ontopofm]

What material is the oem fuel pipe? Steel or stainless steel?

 

[fz1boxer]

Excellent write up

 

[alia176]

What material is the oem fuel pipe? Steel or stainless steel?

I have the dual filler neck and I *think* it was fairly light weight so I'm guessing cast Alum?

 

[alia176]

Is this a photo of what your talking about?
Here's a link to the print.
PDF schematic.
Link to George's web site.
George's 80 Series Land Cruiser and Nissan MQ Patrol

Sorry for the late reply but yes, George's ECU.

 

[I Lean]

What material is the oem fuel pipe? Steel or stainless steel?

It's thin steel, galvanized or otherwise zinc coated.

 

[DiscoCam]

I know that this thread is a bit old, but has anyone else tried this tank in the 80?
I was gonna go with the OEM sub tank, but if this is low profile and holds 20 gallons, I might go that route.

Because a new one of these is ~$60 or so....