If you have a BAT relocation, I was idea storming about fuel pump rewire. The prob is getting a strong 12V to the pump. What about taking the 12v wire that suplys power during crank/ON, run to a relay. Wire a feed from the BAT - and + to the relay and a + from relay to the pump. Giving a perfect stong - and 12v+ directly to the pump. Put the relay and it's wire package in a nice little secure bundle and hide away somewhere in this location.

Any probs? Sounds good?

 

as long as it is properlly fused there should be no issues

 

Other than being illegal and unsafe, it would be fine.

By law, the fuel pump should turn off if the engine stops. This is for safety in an accident, and is why the fuel pump, at least on the S4s, is wired to a relay coming from the airflow meter. If the engine is pulling air, the fuel pump is on. If the engine is NOT pulling air (as in, not turning), the fuel pump gets cut off. If there's an accident and the engine gets jacked around, a fuel line may be split/broken. Normally this will kill the engine rapidly, the fuel pump will shut off, and there won't be any problems. If the fuel pump is wired to the ignition, it will rapidly pump the contents of the fuel tank into an engine bay with hot exhaust parts lounging around. Not good.

If you want to rewire the fuel pump, look at how the stock system is wired (FSM is your friend here). Tie into those lines with your relay. As long as the fuel pump turns off when the engine shuts down, you'll be fine.

-=Russ=-

 

If you just run the wire feed from the fuel pump that gets cut off during no "AIR DRAW" to the relay you acomplish just that.

 

I was toying with this idea...

Most 12VDC relays have a NO and NC contact...
The Turbo II ECU should have a 12VDC (?) switch lead when the boost sensor sees high load.
This would be the low-current trigger for the relay system.
Under low-load conditions, the fuel pump power would just run through the stock wiring.
When under heavy load, it would trigger a relay to take direct power from the battery.

The wire to the fuel pump would be the common high-current lead.
The stock fuel pump wiring would go into the NC lead.
The wire to the battery would go to the NO lead.
This would keep power from the stock wiring to shoot through to the fuel pump until the stock ECU triggers the high load condition.
If the stock ECU is 12VDC trigger, then wire this to low-current side, and the other to ground.
If the stock ECU is ground trigger, just wire the other low-current side to +12VDC.


This would keep the stock fuel pump cut-out system intact and would only switch to full power when under load from the ECU...

Does that make any sense???


-Ted

 

Makes perfect sens ReTed. Thank you for the input.

 

I'd be hesitant to switch my fuel pump over between voltage sources while approaching boost. There will be a momentary lapse in power, and if for some reason the relay fails mid-switch, you lose fuel pressure as you're going into boost. Not good.

Now, you could use a relay of that sort to duplicate the functionality of the resistor pack with some dropping diodes or such...

-=Russ=-

 

The full fuel pump rewire that Dale Clark devised repowers the fuel pump directly from the battery, and works perfectly at lowering volt drop to the pump and retaining the stock 2-speed system. It makes no difference where the battery is, the rewire is still done the same way. But if the battery is in the back, the power wire will be shorter and hence have an even lower volt drop.

Here's the link to the how-to:

http://www.1300cc.com/howto/how2/rewire.htm

And here's the wiring diagram I drew to help me do it:

 

Thx NZ thats a great post.

I mentiond back for the fact it makes it so easy to hook up. I didnt see that post of the fuel pump rewire to see someone was using a relay. I saw people just runing new leads.