Wiring for secondary inline fuel pump

[E30godz]

What kind of wiring would be needed to make a secondary inline fuel pump work correctly?

[E30godz]

bump

[iXer]

You should splice into the feed from the fuel relay if you've got the pump in the engine compartment, otherwise you should try finding the cables that go to the fuel tank in the back and isolate which one feeds the pump.

Why do you need an extra pump? in case the original pump fails?

I see you're boosting the engine, so I can understand that you would wan't to avoid a lean condition, but that's usually a matter of sizing the fuel injectors.. I don't see how the original pump can't handle your fuel demands, from what I hear you need more fuel only when the engine approaches 500 hp. But by then you should replace the original pump altogether with something beefier, and it wouldn't cost much compared to the expenses you have to go to in order to keep the engine happy with all that power.

[E30godz]

interesting....well i wonder what the stock max flow of the fuel pump is? i beleive im going to get some 30 pound injectors and a 3.5 bar FP

[iXer]

For what it's worth, a fellow swede has 320 hp at the wheels on his 325 with the original pump and 366 cc injectors @ 3.0 bar. The boost pressure is 1 bar and the fuel/ignition is properly mapped. There was no sign of a lean condition there.
If you're aiming higher than this I suggest you invest in a fuel pressure gauge so that you can see if the fuel pressure dips at anytime. If it dips at high boost/high revs you should probably get a stronger pump. A recommendation would be to upgrade the dimension of the fuel pipes between the pump and the fuel rail. The original is 6 mm or so.. aim for 10 mm.