View Full Version : Fuel line.

03-05-2009, 12:32 AM
I'm replaced my fuel tank and lines from the tank to the fuel rail. I'm unsure on what size I should use, or what material at that.

I'm swapping in an IS fuel tank/pump I don't know if there's any difference between mine(1984 318i) and the 325is but they aren't the same size pump.

Are there different flow rates for the 2 different pumps? What line should I use, should I run it under the car or through the cabin? (Semi-race interior, stripped, floor exposed, no rear seats, bride seats in the front)

Braided line? Steel? other? Advantages?

03-05-2009, 12:36 AM
Run it like stock....Use good new steel lines and hoses....DO NOT run them through the cabin...Not exactly sure on the sizes though.

03-07-2009, 05:30 PM
Nobody knows the size?

03-07-2009, 06:25 PM
i would think it would be a 3/8" line

03-08-2009, 12:20 PM
I'm pretty sure it's 5/16" for the supply and return, not sure about the vent line, probably 1/4". Run the lines exactly as they were from the factory, they're like that for a reason. Hard lines up to the engine compartment, then run what you want from there to the rail (if you use neoprene, make sure it's fuel injection hose, it can stand higher pressures than the regular stuff.)

The difference between the early 318i and the later model cars, is that the early cars have the intank transfer pump (which has a very fat fuel line attached) which sucks the fuel out of the tank, and supplies it to the high pressure external pump under the door onthe driver's side. Late model cars only have one in-tank pump. Pretty sure that the pump spec's are comparable, as the early 325i's had the same external pumps as the 318i.