Fuel Injection / swirl Pot

[Mike 16]

Hi chaps, I am new to PistonHeads, and new to Injection, I have a Robinhood type 7 and am converting from carbs to throttle bodies with an ECU.everything is going ok with the conversion but now I have to fuel it.

My problem is the tank is stainless and almost impossible to take out, and only has one outlet, and therefore to weld in another outlet I think is impossible, therfore my question is, if I use the low pressure pump to feed a swirl pot in the front end of the car, then thru a filter to the injection pump can I just return back to the swirlpot after the regulator, if I can do that, what about a vent, and where would that have to go to.

Any help will be most appreciated, and any ideas.

Regards...Mike

Edited by Mike 16 on Tuesday 11th March 12:32

[GreenV8S]

It isn't ideal, but I suppose you could tee the feed and return close to the tank. This does mean that the same fuel keep recirculating round the engine which may make evaporation problems more of an issue. I don't see any fundamental need to use a fuel swirl pot but if you choose to then you could use the same approach i.e. lifter pump from the tank to the swirl pot, overflow from the swirl tank teed back close to the tank, higher pressure pump draws from the bottom of the swirl tank and fuel rail return back to the swirl tank.

I wonder whether it would be possible to fit an extra spigot to the tank without removing it from the vehicle. Is there sufficient access to weld it in situ?

[stevieturbo]

One way or another, you will need a return to the main tank, to achieve some sort of decent system.

If you can arrange a system like the top pic, then it will be fine, and it only requires one return into the main tank.
You could do this at/near the filler neck ( I assume you have some sort of filler neck ?? )

Although a better approach, would be the lower pic.


Make sure you use a low pressure pump with good capacity.

http://img99.exs.cx/img99/1834/fueltwo3dc.jpg

[Avocet]

Can you run the return into a "T" that goes into the filler neck or somewhere in that region?

[stevieturbo]

If returning to the filler neck area. Ensure the return isnt restricted, and also that fuel can never flow out of the filler cap when its removed.

But I would say it is an option. Just make it safe.

[Mike 16]

Thanks for the info,I'll try to get a inlet welded to the tank in situ, any tips on making a petrol tank safe to weld, I guess it will need to be purged with an inert gas at least to make it safe.

Regards...Mike

[Jack_and_MLE]

fill it with water, that fairly inert and quite cheap!

It's what i did when I tried to repair the plastic tank in my 21.

Jack

[Jack_and_MLE]

fill it with water, that fairly inert and quite cheap!

It's what i did when I tried to repair the plastic tank in my 21.

Jack

[GreenV8S]

Jack_and_MLE said:

fill it with water, that fairly inert and quite cheap!

Yes, it's really the only safe way. Anything that leaves gas in the tank is going to result in petrol vapour being left too, no matter how carefully you think you've cleaned/flushed it.

[stevieturbo]

Dont just fill it with water. Flush it out thoroughly first, several times, and then fill.

Even then, you might not find too many welders willing to tackle it....just in case.

[BB-Q]

I've welded loads of petrol tanks- the bang's not usually very big if you've let them vent to atmosphere for a few days. does make you jump, though. Another alternative is to pipe exhaust fumes in there from a running vehicle.

[Pigeon]

I fill them with water. And I've routed a fuel injection return line via the filler neck. I had a bit of tube running down inside the neck to make sure the fuel went down.

[v8ian]

If you can mount the fuel pump below the bottom of the tank, with the pickup at the rear of the tank, you may be able to get away without a swirlpot, I dont run one, and have never had any fueling problems, I do rum a large pre pump filter,[AudiV8] as for returns, you can run the return via the filler, I sweated a piece of 5/16 piece of pipe into the filler neck and ran it down to nearer the bottom of the tank, other options are drill the tank at the top and fit a Large Rivnut into that hole, that is a way of fitting a pipe into the tank, or possibly take out the sender and drill the sender plate so a fitting can be added there so you can fit a pipe.
Ian

[freddytin]

Common practice when welding fuel tanks is to purge them with exhaust gasses for a while prior to welding.

[v8ian]

Im dubious about filling the tank with no flamable gas before welding, as there is no visual sign that the gas is present in the tank when you start welding or are welding, at least if the tank is full water, you can see it and you tell if the level is falling, unlike gas.