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Jun 16, 2014 10:59:05 GMT
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Hi I'm plumbing in a fuel injection system into a car atm. The car is old though, and only has one pipe coming from the fuel tank. I don't fancy messing with the tank and putting a new pipe in really.....
But could I "T" the one pipe into two and have it as the feed to the pump and the return? Afterall, the return just puts it back in the tank again??
Cheers
Craig
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Last Edit: Jun 16, 2014 11:00:20 GMT by code109
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Jun 16, 2014 11:15:34 GMT
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In a word no . If your going to the extent of fuel injection you may as well do it properly other wise it wont work .
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Jun 16, 2014 11:50:11 GMT
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Will not work atall then? If I had two pipes then they're goin to the same place anyway?
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Jun 16, 2014 12:35:33 GMT
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Do you mean putting a return in which goes back in to the outgoing fuel line ? Its either just going to restrict flow or not return at all .
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10mpg
Club Retro Rides Member
Posts: 4,253
Club RR Member Number: 204
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fuel injection10mpg
@10mpg
Club Retro Rides Member 204
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Jun 16, 2014 13:25:06 GMT
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If you really can't figure out why this won't wont work, and i'm not being cruel, perhaps you shouldn't be doing mechanical work that involves a degree of understanding and design. The whole point of a return is that it circulates the fuel, allowing pressure to be maintained and regulated at a desired point, In addition to this it keeps the temperature of the fuel stable and therefore the density. There is so much wrong with your question, (it shows a such a deep lack of understanding) that my gut feeling is you shouldn't be messing with stuff like this until you've made a concerted effort to understand basic engineering principles... Study the picture here and have a think, imagine putting your 'loop' into the red circuit, after the injectors, can you see the problem now? Think of it like a hose pipe.....
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Last Edit: Jun 16, 2014 13:31:10 GMT by 10mpg
The Internet, like all tools, if used improperly, can make a complete bo**cks of even the simplest jobs...
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Jun 16, 2014 13:39:23 GMT
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No I mean put the blue return pipe onto the green feed pipe to the pump... The pump has a built in filter aswell
if the pump takes fuel from the tank, can I not just put the return pipe into the system before the pump again? Then I only need one pipe (only one there atm) from the tank....
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VIP
South East
Posts: 8,293
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Jun 16, 2014 13:47:46 GMT
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No I mean put the blue return pipe onto the green feed pipe to the pump... The pump has a built in filter aswell if the pump takes fuel from the tank, can I not just put the return pipe into the system before the pump again? Then I only need one pipe (only one there atm) from the tank.... You do realise that not all the fuel coming UP the fuel pipe from the tank is sent to the injectors and burnt in the combustion process, right? So the excess fuel has to return to the tank. How does it do that down the same pipe that fuel is still coming UP from the tank in?
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Jun 16, 2014 13:59:51 GMT
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This is why I asked...
I just assumed, because of the pressure differences, that if there was more fuel coming back than being used it would just start putting it back in the tank, and if it was using more then was coming back then it would start taking some from the tank?
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Jun 16, 2014 14:09:01 GMT
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It's not how that would be traditionally done. If it could be done like that it would save on manufacturing costs so they would do it that way.
A fuel injection tank has lots of holes in it for pipes coming off. Another use for holes in the tank is breathing. It stops pressure building up in the tank.
There are two possible options for you.
1. If your model of vehicle had a fuel injection variant then get the parts from a fuel injected version. I know BMW in the early 1980s for example, had both fuel injected and carburetted versions of the BMW 5-seires. So did Saab with the early 80s 900 and 99. The parts swap straight over between models without any modification.
2. If you really don't want to make your own hole in the tank for a return line then a place where you could possibly T into would be the bottom of the fuel filler neck where it joins the tank. Depends on how long the neck is... wouldn't work on every car.
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Jun 16, 2014 14:24:15 GMT
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So id need a breather pipe anyway then....? I was just trying to not ruin the tank in any way
I was going to T the pipe as soon as it leaves the tank, so it basically goes back to the tank anyway
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VIP
South East
Posts: 8,293
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Jun 16, 2014 14:38:15 GMT
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This is why I asked... I just assumed, because of the pressure differences, that if there was more fuel coming back than being used it would just start putting it back in the tank, and if it was using more then was coming back then it would start taking some from the tank? Er, how can you have more fuel going back than coming up? You'd have an engine that generates petrol and have solved the fuel crisis! The pressure/flow from the tank in constant because of the fuel pump, what's returning is less in volume and pressure and therefore as soon as it reaches the T it has nowhere to go.
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Jun 16, 2014 14:43:38 GMT
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This is why I asked... I just assumed, because of the pressure differences, that if there was more fuel coming back than being used it would just start putting it back in the tank, and if it was using more then was coming back then it would start taking some from the tank? Er, how can you have more fuel going back than coming up? You'd have an engine that generates petrol and have solved the fuel crisis! The pressure/flow from the tank in constant because of the fuel pump, what's returning is less in volume and pressure and therefore as soon as it reaches the T it has nowhere to go. it would go back into the system and just not take as much out the tank as a result?
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stealthstylz
Club Retro Rides Member
Posts: 14,841
Club RR Member Number: 174
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fuel injectionstealthstylz
@stealthstylz
Club Retro Rides Member 174
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Jun 16, 2014 14:54:22 GMT
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Just checked I guess this is the Hunter. You're gonna need a swirl pot of some sort in the fuel system too. The return has to go to the tank though.
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Jun 16, 2014 14:59:09 GMT
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This was my idea Cus I don't think I explained it very well
Pump takes it to the injectors, any excess fuel is "let go" by the regulator, then put back into the system, anymore that is required is just taken from the tank
what's the job of the swirl pot my I ask? :s
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Last Edit: Jun 16, 2014 15:00:51 GMT by code109
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Jun 16, 2014 15:47:59 GMT
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'Slaps head repeatedly '.
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Jun 16, 2014 16:03:34 GMT
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Ha I'm sensing some frustration? Lol
I know how a normal system is plumbed up, I have worked on my own cars before
I just can't see why that wouldn't work. Anyway, I'm gonna stop now before I start receiving death threats Haha
I'll ask the mechanic down the road
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Jun 16, 2014 16:14:08 GMT
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Swirl pots are used to keep a steady fuel supply to a pressurised system like those used in fuel injection. It stops over fueling and fuel starvation issues.
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Jun 16, 2014 16:19:39 GMT
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Basically imagine fuel at pressure is harder than fuel which isn't pressurised. If you try and push the returning low pressure fuel into the high pressure fuel coming out of the tank it won't be possible. The 'soft' stream of low pressure fuel won't be able to push into the 'hard' stream of pressurised fuel.
I can see what you're trying to say, that you're going to return the fuel pre-pump and that the pump will be outside the tank. You'll put the return into the pump feed rather than the post pump pressurised side. It still won't work.
As I understand it, a swirl pot is simply the device which ensures the pump always has a head of fuel to feed off so the pressure is constant going around corners and up hills. May be wrong on that but I've never had to fit one so never bothered to try and find out.
I think if you want to do this you're simply going to have to acknowledge that this conversion will require changes to the fuel tank. As I said before, you may be better off replacing the tank with an injection version. I guess there wasn't an injection variant of the Hillman Hunter so your best bet, if you don't want to damage the original tank is to research alternative tanks you might be able to get from a scrapyard. If you can stomach the cost then custom fuel tanks have been around as long as cars themselves. You can order them online by supplying measurements.
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Last Edit: Jun 16, 2014 17:48:43 GMT by ejenner
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Jun 16, 2014 17:03:56 GMT
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Could you not just return it via the filler neck of the tank if easier ? Usually there is a couple of vents there anyway
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