Is This A Stock Fuel Pump?

[hairdryer33]

Bucket of petrol, pumps fine. Took fuel filter off in engine bay pumps fine so no blockage in line anywhere. Im running a stock regulator

[hairdryer33]

Anyone else have troubles putting a walbro gss341 aka 255 through stock relay? Wondering if wiring direct could fix the issue but for now the gtr pump is back in

[Badgaz]

with the 255 you shouldn't need to...i run a dw300 on stock wiring.

[hairdryer33]

Ok thanks

[Dose Pipe Sutututu]

Bucket of petrol, pumps fine. Took fuel filter off in engine bay pumps fine so no blockage in line anywhere. Im running a stock regulator

you should check fuel pressure, it might pump but that doesn't mean it will be supplying the right amount of fuel

[hairdryer33]

It not, as cruising is normally 12.5 but running 16 is way too lean

[GTSBoy]

I don't think you are understanding what you are being told.

Just because the fuel pump will flow a good quantity of fuel with no restriction (ie no back pressure - just an open hose into a bucket) does not mean it will continue to flow a decent amount when you apply back pressure. In fact, even a brand new perfectly good pump flows less with back pressure. But a borked pump could well flow what looks like a decent amount wide open and reduce to a trickle once working against the back pressure of the regulator.

Now consider what you said above about cruising. When cruising the fuel flow rate needed by the engine is low. Further, there is vacuum in the inlet manifold so the required fuel pressure is not real high either. Both of these things could allow the pump to flow enough to keep up with the injectors. But put your foot down and the fuel flow demand goes through the roof. On top of that now you have 10+ psi of pressure in the inlet manifold, instead or 6 or 8 psi of vacuum. So now the back pressure on teh pump has gone up by 16 psi or so. And the poor old thing stops being able to keep up and you lean the f**ker out.