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Fuel lines?
Posted: Tue Apr 22, 2008 3:47 pm
by silkcity
Hello to all. Found this place doing web search for a feuel system schematic for my 1993 Legacy Automatice FWD. So my question is, there are three lines going into the fuel tanks. I assume that one is the supply (no pressure), one is the return (under pressure) and what's the third one for? I disconnected it at the engine and ran the engine for a few seconds and there is no fuel there. Also, there is an inline valve type of thing on that line under the cab just before the fuel tank. What is that? Is this line for fuel vapor? If anything flows in this line, in which direction does it flow? from engine to tank or tank to engine? Thankyou all.
Posted: Tue Apr 22, 2008 4:35 pm
by keirnna
I believe that is an evap lines, but I am not sure. I would have to check my FSMs to be sure.
Posted: Tue Apr 22, 2008 4:41 pm
by silkcity
That's what I thought but i need to be sure. It it is an evap line then the flow would be from tank to engine, right or wrong?
Posted: Tue Apr 22, 2008 5:36 pm
by 93forestpearl
Your supply from the tank is at rail pressure. Your pump in the tank supplys fuel at high pressure to the rails. The return is low pressure since it is after the fuel pressure regulator. The evaporative line should have a roll-over valve in it so you don't get your evaporative system full of fuel if the car end up on it roof.
Posted: Wed Apr 23, 2008 4:40 pm
by silkcity
ok, so here is where my confusion is........there is a line going from the fuel filter into the fuel rail. I thought that this was the supply line being that it comes directly from the filter. But when I disconnected it there was no pressure present in the line. The other line, which I thought was the return line because it goes from the fuel rail to the tank, no filter, was under pressure when I disconnected it. Is something wrong here? Can someone post a picture of what their factory setup looks like on a NA 1993 Legacy? Thanks.
Posted: Wed Apr 23, 2008 7:07 pm
by Legacy777
When did you disconnect the line?
The fuel pump will turn on initially to prime the lines and then turn off.
The return line technically shouldn't be under pressure, but if the tank has pressure on it, the return line will also have pressure on it, because the fuel pressure regulator is keeping pressure on it (I believe this is correct)
My only other thought is that the supply & return lines got mixed up....but I doubt that unless someone replaced the hoses. From this picture it looks like the supply line is in the middle, or below the return line.
http://www.main.experiencetherave.com/s ... acket2.jpg
Posted: Sun Apr 27, 2008 2:12 am
by silkcity
the key was off. when i disconnected the 'supply' line there was no pressure present, when i disconnected the 'return' line, there is pressure present. I asked some one if i could see they're fuel line setup, the guy had a turbo version but same year. I don't see why the arrangement would be different, but it was. From the lines coming out of the firewall the top line was return, the middle was evap and the bottom was supply. On my car, out of the firewall, the top is 'supply', the middle is 'return' and the bottom is evap. Coming from the engine it's in the same order. Tonight I'm gonna disconnect the lines at the firewall, turn the key on and see where the fuel is shooting out of. That will be my supply. The evap line should have that inline valve that I mentioned before just before it enters the tank, so that would leave me with the return. Here's where I need you help; on the engine side: which line is which? Thanks again to all who have replied.
Posted: Sun Apr 27, 2008 2:30 am
by Legacy777
