Defender 90 300TDi dual tank veg oil conversion

I plan in January to convert my 300TDi defender into a dual fuel (veg oil & diesel) vehicle.

There are several options including just pouring veg oil at various mixtures into the existing diesel tank from 1/10 to 3/4 depending on time of year etc but they have their issues. My plan is to fit the late 300TDi/T5 rear tank for diesel only and then use the existing tank for any mixture of 75-100% veg oil depending on time of year.

I'm planning on replacing the existing fuel lines just as a matter of course and fitting a second fuel gauge to the second tank just so I have all the info I want (Yes I could have the changeover switch change the fuel gauge as well but I'd rather be able to see both at the same time). I will build into it a warning sounder in case I accidentally switch things off with it still running veg oil and when it's all up and running and working properly I will build an electronic control unit to do everything (I'll make this available if anybody else wants it).

So....

No point in re-inventing the wheel so to speak. There is a good thread on the physical fitting of a second tank here - http://www.landyzone.co.uk/lz/f7/td5-fuel-tank-into-300tdi-defender-164418.html : I will be using the first part of this and then feeding the fuel output through to the engine bay.

My current plan, maybe, is to blank off the return fuel feed hole on the rear tank and any return fuel goes to the front tank. This will avoid veg oil being returned to the rear tank and any small amounts of unused diesel will go into the veg oil where it will not cause any issues (see later)

I will use clear fuel pipe for the front tank and blue for the rear just so that I can keep them separate. I plan to insulate the veg oil pipe.

My plan, at the moment, is as follows:

front (veg) tank - output to go through a water/fuel heat exchanger to warm up the veg oil and then send it through a heated fuel filter to a 3 way valve....

rear tank - output to go to the same 3 way valve....

3 way valve - default (i.e. no live feed) will be rear tank to output with front tank to output when positive feed received from a switch on dash.

output of 3 way valve goes into existing fuel feed setup just as it would now with return fuel feed going to front tank.



So that is my CURRENT plan.

Can anyone see any issues?

How much fuel actually goes back to the tank via the return feed? Do I need to re-think this? Maybe have a 2nd 3 way valve to send the unused fuel back to the tank it came from? (this would mean that at switch over small amounts of veg oil might go into the rear tank but these really would be small amounts)

Regarding fuel pumps: would there be any issues in having two fuel pumps fitted prior to the 3 way valve (obviously the only one powered up would be the one from the fuel being used) these would obviously feed fuel already under pressure to the existing fuel pump...... Would this cause as issue? Could I dispense with the mechanical fuel pump?

Has anyone got a diagram of the current fuel feed setup?


I know there are a lot of questions but once I've got all this running with information in here it will be a good resource for anyone else planning on doing the same thing.

I will add a way of checking the temperature of the fuel prior to switching as a temporary measure until it's up and running then I will build this into the electronic control unit.



Costs:

2nd tank £40-50 (2nd hand)
2nd tank bracket (£40)
2nd tank protector (?)
2nd tank gauge (£15)
fuel pipe
2 x electric fuel pumps
1 x heat exchanger (£60?)
1 x heated fuel filter (£60?)
2 x 3 way value (2x £60)
modifications to the existing exhaust system

So in diagramatic form:


Currently:

This is the current setup i.e. one tank with the output going to the mechanical fuel pump, then to the existing filter and then to the injection throttle body with the return fuel feed going back to the existing fuel tank via the injection throttle body.





Option 1:

This is the simplest setup using the existing fuel pump and feeding that with either heated veg oil or diesel and the return always going to the front tank.





Option 2:

This is the same as option 1 but with the return going to the tank that is currently selected. This will send a VERY small amount of veg oil to the diesel tank at changeover but not enough to cause any issues on a landrover.





Option 3:

This option is the same as option 2 but provides each fuel feed with it's own electric fuel pump with the current fuel pump dispensed with (or I could use that in addition to the electric one)

Hi, sorry to resurrect an old thread.

Did you progress with this? Has it worked in the long term?
I am mid way through setting up what you describe as option 1 and just wondering if I can learn anything from your experience?

Thanks

Rarms said:

Hi, sorry to resurrect an old thread.

Did you progress with this? Has it worked in the long term?
I am mid way through setting up what you describe as option 1 and just wondering if I can learn anything from your experience?

Thanks

Click to expand...

It would be nice if you wen to the intro thread, so we would know whom we are about to abuse ....