no fuel line pressure

[john911sc]

on my 1974 914 2.0....i have no fuel line pressure....the fuel pump works great.....new fuel lines in the engine compartment....new fuel filters....i followed the 2.0 injection diagram when putting in the new lines.....now there is no fuel pressure????...i have two lines coming out of the body to the back of the car....a 9mm and a 7mm...one is supply and the other is return....if i have them mixed up..would this cause the problem....how do i know which line is supply and which is return...thank again...john c.

[Dave at Pelican Parts]

Supply is 7mm, return is 9mm. It probably would not give you zero pressure if you switched them.

If you hooked up the fuel pump up backwards, it probably would give you this problem. The "D" port goes to the high-pressure loop of the fuel system, the "S" port to the 9mm line through the center tunnel, and the "R" port goes to a Y connector that goes to the 7mm line in the center tunnel and to the fuel pressure regulator.

I am not sure, but I think hooking up the electrical connector on the pump backwards will also give you zero pressure.

Have you checked the pressure with a gauge?

--DD

[john911sc]

on the injection diagram it shows the "s" suction going to the filter.....the "d" goes to the return 9mm hose....and the "R"....goes to the "y" outlet.......which way is correct?????

[Dave at Pelican Parts]

"S" is suction. The 9mm line goes to the filter, and a 7mm line comes out of the filter and goes to the "S" port of the pump.
"D" is "druck", which is German for "pressure". That goes to the fuel rail and the rest of the high-pressure loop.
"R" is for return. The fuel pressure regulator and the 7mm line in the tunnel both connect to the "R" port on the pump, by way of a Y fitting.

--DD

[john911sc]

i will give it a try this weekend and let you know the outcome....thank for all the help....john c.