I'm rewiring my walbro pump, on my 90 GXL- S5, so I've got the resistor pack.

Now, the only reason to use the fuel pump resistor is to drop fuel pressure, and therefore fuel economy under light load in TII's

I understand it will also lengthen the life of the pump as well.

Anyways, If you bypass the resistor relay, it'll run rich at idle and some points just outside of closed loop.
Well, I have an S-AFC, and I'd prefer a constant voltage to the pump just to make tuning a little more straightforward.

I'm assuming I can just run a wire right form the battery to the pump, with a relay on it, and not worry about the resistor pack? (I can lean out idle and such with the S-AFC of course)

Just making sure.

 

Full 12v, tune down the idle with the SAFC.



But

Batt+ -> Fuse -> Relay -> Pump

 

The 12v is not what regulates the pressure at idle. The FPR does. That's my story and I'm sticking with it. The switch to 12v is for more volume at boost. I'm talking stock fuel pump and regulator. Nothing else.

 

Then how do you explain why they added the resistor circuit to the S5 N/A's?
Fuel pump life is a good idea to me.

 

I've also heard that the pump, especially on the TII's will overrun the FPR at idle with 12v- making it at rich idle.
blah blah

 

9volts to not wear out the pump. Your a heartbeat from making me put my fuel pump pressure rig on the car and jumpering 12v to it at idle. I don't wanna.

EDIT: OH! I don't have to. At one time I put my turboii pump in my N/T car(which has no resistor). The idle pressure did not change at all. There. Been there, done that. Got better things to do this weekend.

 

Overrun isn't quite the right word but you're right. The only thing that causes the FPR to adjust is manifold pressure. Even if you increase the pump pressure, the manifold pressure stays the same, so the FPR's plunger stay in the same position. Because the restriction hasn't changed, the increased pump pressure will result in incresed rail pressure.