Joining Fuel Tanks

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20 May 2016 06:41 #1 by Peter Davis
Peter Davis created the topic: Joining Fuel Tanks
One annoying thing about having a vehicle with dual fuel tanks on different sides of the vehicle esp since long fuel hoses at petrol stations have been removed, is filling up the truck. Having to move vehicle around the server to fill other side can be a pain and time consuming waiting for free bowser.
So my question is has anyone joined the tanks together so it fills both tanks up at the same time?
If yes what size hose did you use and did you add a breather hose to both tanks?

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20 May 2016 09:05 #2 by mort
mort replied the topic: Joining Fuel Tanks
Peter,
This is a topic I was going to revisit soon as I have been looking for bigger tanks for some time and am now getting some made.
In the past I have the same problem and got around it by filling up at different stations 1 tank at a time or Hilda will go inside to tell them that I am not driving off...yes a problem.
What I had planned was a transfer pump from 1 tank to the other but not at that point yet,so if something better comes up that is how I will go.

Martyn

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20 May 2016 13:17 #3 by Tony Lee
Tony Lee replied the topic: Joining Fuel Tanks
Best to crawl underneath and figure out where to run the pipe. Would need to be 1 1/2" to 2" to provide useful flow rate. Connecting the bottoms of the tanks would be ideal but then the pipe would be very vulnerable to damage and to get it high enough to be safe would mean being too high to work.

Pump would work but would need to be 100 L per minute with a way to shut it off automatically.

Depending on what sort of body you have, you might be able to run a filler pipe across to the other tank but I think it would be very prone to air locks, slow flow and constant triggering of the nozzle shutoff.

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20 May 2016 16:40 #4 by Peter Davis
Peter Davis replied the topic: Joining Fuel Tanks
I was thinking about 3/4 of the way up, above the drive train so that sticks and rocks didn't take it out and if it did only 1/4 of a tank would be lost (mind you from both tanks). I was trying to find flow rates out. 1 1/2 inch pipe would allow about 130 lpm of water to flow with gravity. Diesel would be a bit slower. 1 1/4 is about 90 lpm, 1 inch is 60 lpm.
Using the air bags to tilt the vehicle over would probably help too.

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20 May 2016 17:50 #5 by Ewart and Vivian Halford
Ewart and Vivian Halford replied the topic: Joining Fuel Tanks
Yes haven't we all, I have thought about finding the filler off a 80 series and see if that would work but still on the to do list.

A mate was telling me he nose some one that has mad a fuel tank for his roof rack made out of grey sewage pipe and recon that the diesel dose not effect it, not sure about that but it got me thinking I may be able to make a filler pipe out of it to run to the other tank, not sure if there would be room under a bus body.

Cheers

Ewart oka 365
0428911147

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20 May 2016 20:04 #6 by mort
mort replied the topic: Joining Fuel Tanks
I have been thinking about this today and as my tanks are being made as we speak or so he says I can make adjustments now for future hook up.
What will work is a spigot say 3/4 or 1" on each tank connect a suitable hose with a pump of whatever capacity you need and switched from 1 or both tanks now as you fill 1 tank the pump is also filling the other and you can run a clear hose say 1/2" from 1 tank to the other so as air is displaced from the tank that is being filled via the pump and into the tank filled via bowser when the tank is full fuel will be forced through clear hose you will see it and turn off pump and continue filling till 2nd tank full.
It will be easy for me to get done on tanks being made as no fuel used yet but on existing tanks you couldn't drill and tap as too thin so the easiest would be to weld a thick plate then drill and tap or weld a spigot on but the danger is the existence of fuel if you dont know what you are doing you will be another statistic and I wont take the risk of giving you ideas on how to kill yourself or even worse blowing up an OKA but it can be done,its what I will do but exactly how or what size I dont know until I am ready to do it.

Martyn

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20 May 2016 20:31 #7 by Ewart and Vivian Halford
Ewart and Vivian Halford replied the topic: Joining Fuel Tanks
Nice Martyn, put the OKA before us lol. I was thinking I could get the new lockable fuel filler from oka and glue and clamp to tank and then clamp filler hose to filler cap.
I was wondering about the breather and ulage , I thought if I put a peace of pipe on the breather to maintain ulage but then I thought over time the fuel may come out the breather. In my case I may be able to get some extra storage before the tank as if I were on the move it would drain in to the main tank as I traveled, I use a electric fuel pump to transfer from aux to main as I drive.

Good topic keep it going.
Cheers

Ewart oka 365
0428911147

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21 May 2016 05:53 #8 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: Joining Fuel Tanks
The decision was made for us when the RAAF specced 374 with only one tank on the LHS. The RHS tank position had a heavy duty shelf to carry a battery bank. I had two poly tanks made to fit that bracket to carry water (140 litres).
Then in the position where the Oka water tank fits I had an aluminium fuel tank made, runs from the rear of the front spring hanger to about 400mm short of the rear diff housing, holds 140 litres of diesel.
The filler neck is just in front of the LH rear wheel so is directly behind the existing tank.
The fuel in the tank is pumped into the Oka tank as required by one of those little square Facet electric pumps. I drilled and tapped into the top of the existing tank 1/4 BSP for the transfer hose from the pump, so the tank is thick enough for 1/4 BSP but a bigger fitting might not have enough purchase, the tank material would be nearly 2mm thick I'd reckon.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.

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21 May 2016 08:18 #9 by OKAPETE
OKAPETE replied the topic: Joining Fuel Tanks
Here is a pic of fuel crossover tube as fitted to Oka 383, previously 'Fat Albert' that was fitted with 6.5 v8 Chev and Allison AT545 in 2wd configuration, soon to be Cummins and Allison 5 spd with Lomax transfer case (when the owner finds a big enough "round tuit" to actually spend some time on it).
Its 3mm wall pipe bent to shape and fittings into the end drain points on the tank with ball valves at each end to shut off if required,or not as the case maybe.
A bit slow to fill from one side but not too bad if you drinking a coffee/beveridge at the time of fill.
With both valves open it draws down evenly from both tanks.

Pete.

Chaplain. Won x One Chaplaincy.
AM SAE-A. AAFRB.

Oka 224. 363. 383.
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21 May 2016 08:49 #10 by outyonda
outyonda replied the topic: Joining Fuel Tanks
Pre tend your a truck
I fill up at truck fast flow bowsers, xtra long hoses to fill both sides

OKAs 091, 093, 094, 113, 346x6 & 405
The following user(s) said Thank You: 210greg

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21 May 2016 21:14 #11 by Tony Lee
Tony Lee replied the topic: Joining Fuel Tanks
"A bit slow to fill from one side but not too bad if you drinking a coffee/beveridge at the time of fill."

Possibly because of the restriction due to the tiny vent lines. Removing the fuel cap might speed it up

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21 May 2016 22:18 #12 by Frank
Frank replied the topic: Joining Fuel Tanks
"Possibly because of the restriction due to the tiny vent lines."

and if your vent lines are like mine they are secured with cable ties to the crossmember that supports the gearbox, effectively restricting them to almost nothing.
Only discovered because I cut the floor out to work on possibility of cable change to gearbox.

Frank & Christine Thomas

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22 May 2016 13:48 #13 by Peter334
Peter334 replied the topic: Joining Fuel Tanks
When we had to fill the second tank up I just threw the nozzle under the oka pull it through and a way we went , a little was left on the ground but not much ,Kay was on the bowser side and shut it off when I said and held down the trigger till I hung up not to hard , and just use the truck ones they are long enough.

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22 May 2016 20:18 #14 by Ralley
Ralley replied the topic: Joining Fuel Tanks
If you go to a proper truck place you can just use a pump on each side. It's a hassle any were else.
The following user(s) said Thank You: Paul

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23 May 2016 14:56 #15 by John and Bronwyn
John and Bronwyn replied the topic: Joining Fuel Tanks
When I purchased 191, the previous owner had replaced the fuel tanks and had included an equalising connection between the tanks. I replaced the PVC hose and valve with better components (1 1/4 in fuel hose and a brass ball valve with seals for the job). PVC is not a good idea, the diesel will leach out the plasticisers which make it flexible and it will eventually crack. Mine hadn't cracked but was quite hard.
The line runs across below the tailshaft and just behind the transfer case (NP205). It is a bit vulnerable.
To protect the line, I installed it inside a piece of PVC pressure pipe, although in retrospect a piece of poly pipe would be tougher. It took a good bit of fiddling to install both the fuel line and the protection sleeve and clamp it all up, but we got there in the end. To stop dirt, sand etc getting between the protection sleeve and fuel line, the ends of the sleeve are sealed with duct tape.
The valve is installed on the passenger side, I refuel from that side. I normally run with the valve closed.
Filling rate is OK, it keeps up with a normal flow pump although a bit of slope (or tweak the airbags) helps. It is a bit slow to keep up with a high flow nozzle when the tanks are nearly full. Larger breathers would probably help.
I have needed to weld one of the tanks, and it is possible to do it safely. It is also possible to make a big bang, when I was a kid someone about 1/2 a km away did. Enough said....

Cheers, John

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