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200 TDI leak off / return pipe.


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Basically, ive got a petrol Series 3..

Am going to convert to 200tdi.

Question being, how is best to connect up the return fuel pipe? Should i get the proper bit that screws in the tank, from a diesel, so it has the feed and return pipe? Or just drill and solder a fitting to the one i already have?

Then it gets complicated... I've got dual fuel tanks. The feed goes through a diverter switch, connecting either tank, and the fuel gauge sender of the relevant tank. Are there any diverter switch that switch feed and return? Or will i need to get a seperate switch and link the two some how?

Any thoughts on this / how to go about linking two switches?

Cheers

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Have a look at the system on my 109 on my blog - the taps have an extra return line valve to automaticlally connect the feeding tank to the return system. You could just run a return to one tank directly, but you'd have to make sure you always use that tank before the other if both were ever filled at the same time, even partially, and keep an eye on the level in the tank with the reurn as Tdis send an awful lot of fuel back to the tank and you could end up with an overflow.

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I used the genuine return line valves, but they are now rare, horrifically expensive and the linkages between them and the main tap spindle are unavailable. The threads are also an awkward size to get pipe fittings for. Your easiest option would be to use a second tap identical to the feed tap which you would operate separately. This may be a little more effort in normal operation, but would be more flexible (as well as cheaper and simpler) in allowing you to feed from a holed tank and return to the other intact tank if you suffered damage off road.

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not twin tanks though....

My original replacement tank and the post-crash replacement tank both came with 2 ports for fuel - one for pickup and one for return, one of them being blanked off. The original suction is in one, and being unable to source a second for the return I made my own. If you can source a second then it'll be a striaght swap.

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Nice to be here. Only so much I can do on a land rover with just an adjustable spanner, grinder and welder before getting stuck :D

Thanks for the replies :)

At uni with discomikey so already hassled him a fair bit for info about 200 tdi conversion.

Money being an issue, think im going to have to cut the tank(s) and buy / make a return port for them, just make sure its sealed well. I know only too well how much of a person I'm not that keen on diesel is (for finding holes). :/

Tap wise, cheapest option seems to get another diverter tap at roughly Ā£50, so may, as you originally said, return to the main tank, and just always feed from that one first after filling up.

Cheers

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you can also loop the return in a T with the feed line before it goes into the filter.

This is what the vegetable oil boys are doing to keep the temperature of the fuel up.

Daan

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That could suit me nicely actually. Even simpler again.

Does temperature of diesel have much of an advantage? Or is it mostly veg oil affected by temp?

How does it run like that - does the leak off pipe push out more fuel than the pump is drawing, and some pushed back the feed line? Or i suppose, itll always be less.. but when reducing revs, and more fuel is being 'leaked off' will it feed back into tank,? Or pump draws enough to keep it in a loop once it leaves the tank?

Would i need one way valves anywhere?

Cheers for all the help.

Quick other un-related question... When going into reverse, am i suppose to hit my hand on the dash??

Mikey.

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Running the return to a T in the lift pump feed can work, but if you get any air at all in the system, it won't bleed out - that's the point of the return running all the way to the tank.

For running on vegoil, there is the benefit of the fuel being warmed before entering the filter. For diesel, this is only useful in the coldest of winters. I tried doing this on my 109 and it causes a lot of running problems if you have even the slightest air leak as it accumulates and causes running problems, making the engine statrt difficult and causing the engine to cut out at low rpm. I would advise against it - a return to the tank is much more reliable and ultimately safer - the engine ying on junstions ca get pretty dicey.

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Just brain storming here:

If you use the dual tank switch it has an electrical contact for the gauges, I think?

I think you can use an electric pump for diesel, so why not have two pumps, one for each tank, selected by the switch electrics, and have the returns plumbed into the pipe work?

A bit of redundancy, with two pumps, yet simple enough.

G.

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There's a fellow on here named discomikey. He converted his petrol s3 to 200tdi, I'm sure he will help you if you ask him, or perhaps he may chime in here!

chime! the way i did it with a single tank, was to use the standard system from a diesel.

although i think a better way to do it with dual tanks would be to tap the return back into the fuel filter housing, this can sometimes make fuel bleeding slightly more complicated but 95% of the time its fine anyway, especially as the engines are self bleeding.

an interesting thought, where are you going to put your battery?

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The engine is self bleeding because it sends any air back to the fuel tank where it's vented! Plumb the return into any part of the feed and you'll build up air in the filter housing, causing the engine to splutter and die at low rpm unless you have a 100% airtight system and have bled the system meticulously. It's not generally a good idea.

As for the twin electric pump idea, those switches won't last long handling that much current, and what do you think you will gain? You'd need another system to switch between sender units for the fuel gauge, or would need twin replacement gauges, and all to what benefit? The mechanical lift pump works well, doesn't need any mods or extra costs and doesn't add a load to the electrical system.

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I agree on the return - has to go to the tank; on my 109 I tapped into the hose that connects the two upper chambers of the tank. Simple, as it used one of the "tee" fittings from the vacuum manifold on the petrol engine.

As for the switch, what do you gain? Well, you gain a simple system that switches both supply and return to the relevant tank that uses standard LR kit.

If I was doing it, I'd fit the pumps on relays, but you point about the gauges is well made.

If you rewired the switches so that the 12V supply came from the fuse (same as stop solenoid), then to the tank Switch, then on to the (either/or as switched) relay, parallel with the gauge, and finally to earth through the variable resistor in the tank, then that would work.

Another fringe benefit is that you could wire a switch into the relay supply and have it as a sort of anti theft measure. Or just pocket the two relays when leaving it!

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I still don't see the benefit of electric lift pumps over the engine driven pump. If you were to use a second feed tap, complete with cradle and sender switched, for the return line, then you could use the switches on that second tap assembly to control the pump relays (the switches would burn out quickly handling the full load themselves), while using the switches on the feed tap to change the gauge sensing, but to what purpose? The only benefit would be if you plan to have a dual fuel system with one tank of diesel and one vegoil, with independent fuel filters between the pumps and the feed selector tap, with the tap running directly to the lift pump to ensure the quickest and cleanest changeover between fuels with so little fuel volume between the tap and the engine. Otherwise, it's an un-necessary expense and complication.

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Well, the standard switchover tap only switches one fuel line, but the need to return the diesel spill return line means there is a requirement to switch the feed and the return. You can't rely on remembering to switch the spill return over, and you'll soon have an empty tank if you don't as there is a LOT of fuel coming back on the spill return.

This way the electric part of the tap switches the supply, and the mechanical switches the return. Your point about the gauges is right - not thinking straight. Mind you, a switch over relay operating the pumps may solve that, though I've no idea about current ratings on switch over relays. Nah, scratch that, it wouldn't work. You'd need a relay that switches two separate isolated live feeds, one to the pumps and one from the gauge to the tanks.

G.

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Anyway - as I said, I was just brain storming - throwing half baked ideas out there to progress discussion toward a viable solution.

G.

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Thanks for all the replies. Been v. helpful :)

I was mixing about your ideas and what's been said, this afternoon and thought this may work....

-> Separate supplies from each tank, through diverter tap and to fuel filter. (As it is now.)

->From fuel filter through de-aerator - this: http://www.oilybits....r/prod_132.html . Or similar. Found the link for the one i want earlier, but lost it again :/ -

->De-areator feeds the injection pump.

->Leak off rail feeds back into de-aerator, gets automatically de-aerated, and re-fed to injection pump. Means less fuel is being taken from the tank each time so less sh#t going through the filter, and less chance for air to enter the system.

Maybe little more expensive than separate tap, or connecting up relays to operate fuel guage sender, and a return line / feed pump, etc, but seems to me like it would be beneficial even if i didn't have dual tanks.

an interesting thought, where are you going to put your battery?

Erm,... By that i assume it doesnt fit on the tray.. ->Does that mean i can cut out the battery tray and save time? Currently repairing chassis, and not done the battery tray yet. <-

Im thinking either on my lap, or make up something to go in the tub next to the spare or something along those lines.

Cheers

Mikey

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I see what you're trying to do now - create a system that won't allow a tank overflow despite having separately operated taps. You could rig something so that the switches each controlled multiple relays, one each for the gauge connection and the other relays to activate a dash light or buzzer to indicate cross-selected valves. It could be done with some planning, using several relays and a couple of buzzers, working on the doubl-live principle that operates the alternator charge warning light, but it'd be a pain to wire up and probably not much cheaper than finding the correct original parts. Getting in the habit of checking both taps are selected to the same side is going to be easier and cheaper, I think.

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I was trying to keep to only one tap, to keep it simpleĀ®.

You could also just copy the XJ6 system (dual tank). They had two pumps in the series 1 versions, thereafter they had one pump with two inputs. Mind you, they didn't have the spill return to worry about.

G.

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Oh, and it may be possible to keep the battery in the front, I did with my di200. The intercooler pipes may get in the way of this, but what I did was cut of one of the legs of the battery tray, and I also cut the steering relay guard a bit, and was able to shuffle the battery forward so it sits almost against the front panel.

I had to ditch the standard battery retainer, and make up a simple strap across the battery. I'll have a look around and see if I have any old pictures on the PC - I've locked up for the night so can't take a photo.

Your alternative is to mount it in a tray between the seats - assuming you're not using the middle seat. So long as it's secure and won't drip acid on you in a roll over situation you should be fine.

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Erm,... By that i assume it doesnt fit on the tray.. ->Does that mean i can cut out the battery tray and save time? Currently repairing chassis, and not done the battery tray yet. <-

Im thinking either on my lap, or make up something to go in the tub next to the spare or something along those lines.

Cheers

Mikey

yeah, the timing cover clashes wiht the back half of the battery tray, most poeple, including me, cut the whole tray off, and put the battery under the passenger seat, although your secondary tank will be there. i have seen the battery where it should be with a TDI conversion once but it was a tight fit. the best thing to do is get it back up to a rolling chassis, put the engine and box in, and see how much you need to take off it. although it wont fit straight in with the full battery tray there. so some measuring and pre cutting should get the first cut and enough out to fit the engine, then see what youre left with

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