Veg oil system control design help.

[Wheresthedog]

hi all

I'm working on a veg oil conversion for our (1997) 110 defender and have some ideas of how I'd like to control it but my auto electric knowledge is poor and I was wondering if anyone could help? I've contacted a few auto electricians and no one wants the job.

I have bought a stack pro water temp gauge which can be programmed to act as a switch once a certain temp is reached:

52mm Auxiliary Gauges: Pro-Control - http://www.stackltd.com/instruments_pro_control.html


And an on (veg) / off (diesel) / on (purge) 'master' carling switch:

The plan is to start on diesel and once the water (engine) temp gauge reaches 70c the engine switches to veg oil.

A minute or so before the journey's end we will switch to 'purge' and diesel will be drawn from the diesel tank but the unused fuel will be returned to veg tank to clear the lines of veg oil ready for the next start up.

He's a schematic of the system:

There are 3 x 3 way solenoid valves and a 12v diesel pump (veg oil is pumped via a mechanical pump and will always be in operation).

On / Veg mode: 1, 2 and 3 and diesel pump is powered = veg oil drawn from and returned to veg tank in its own loop and diesel is drawn from diesel tank and used to run vehicle. Once stack pro water temp gauge reaches 70c: 1, 2 and 3 and diesel pump become unpowered = veg oil drawn from and returned to veg oil tank (engine now running on veg oil).

Off / Diesel mode: 1, 2 and 3 and diesel pump are powered = diesel drawn from and returned to diesel tank.

Purge mode: 1 and 2 are powered, 3 is unpowered = diesel is drawn from diesel tank and returned to veg tank.
Although diesel mode is activated in the carling switch off position the solenoid will be powered as the vehicle will be in veg mode most of the time and will use less battery power this way.

I'm not sure what I need to make this system work (relays? Diodes? Etc) or indeed if there are any problems/impossibilities with what I've proposed?

Any help and advice would be much appreciated. (12 volt planet said they can help with all the parts but can't help with the design).

Cheers

 

[SparkyChick]

Unfortunately @Wheresthedog your images don't appeared to have worked, and I'm not clear what 1, 2 and 3 are? Solenoid valves?

My gut feeling is a combination of diodes and relays, but more than that is difficult as some of your explanation doesn't quite make sense. On/Veg mode: 1, 2 and 3 and diesel pump powered, Off/Diesel mode: 1, 2 and 3 and diesel pump are powered. Which is it, or would it be clear with the pictures?

 

[The Ghost]

Would it not be a lot easier to get a converter for veg oil and then put that in your tank?

 

[Wheresthedog]

I'm having trouble uploading pics for some reason - yes they'd help make things clearer.

View attachment 35692

 

[Wheresthedog]

Ahh it worked!

 

[Wheresthedog]

Here's the 3-way (on/off/on) Carling switch actuator:

View attachment 35693

 

[Wheresthedog]

but more than that is difficult as some of your explanation doesn't quite make sense. On/Veg mode: 1, 2 and 3 and diesel pump powered, Off/Diesel mode: 1, 2 and 3 and diesel pump are powered. Which is it, or would it be clear with the pictures?

You need to read it all

"Once stack pro water temp gauge reaches 70c: 1, 2 and 3 and diesel pump become unpowered = veg oil drawn from and returned to veg oil tank (engine now running on veg oil)"

 

[PEG]

Hi,let us assume you are direct debiting the duty

Do you have two separate tanks? If so,you will have to set up a method of diverting the fuel return lines,or you will get over spill and dilution!

The main problem with these kits,is if you stand behind while the engine is running,you feel like ordering a steak and kidney pudding

Hang on,just seen solenoid 3...fair bit of pipework,then.

Nope...second edit...i stand by my initial comment. Unless there is some space-age sampling and ECU,you will get,at least dilution,or mixing,due to change over from one fuel to the other,will return,the remnants of the previous fuel supply, to the other tank.

 

[Wheresthedog]

Yes two tanks (see schematic above). The system works well - there can be no overspill in this setup. Need help with the electrics only.

 

[Wheresthedog]

Nope...second edit...i stand by my initial comment. Unless there is some space-age sampling and ECU,you will get,at least dilution,or mixing,due to change over from one fuel to the other,will return,the remnants of the previous fuel supply, to the other tank.

It doesn't matter that there's dilution or mixing of the veg oil. It only matters that the diesel tank doesn't receive any veg oil. The diesel only serves to start the engine from cold.