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Fuel pump direct wire mod issues

Majorgrief
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Majorgrief Rookie

Majorgrief

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Posted

Hi all, 

I've just had a walbro 225lph pump put in my series 2 stag, so I've taken the opportunity to direct wire the pump in. Ive put in the relay, run 8 gauge wire to it (via fuse), used the old active on ECU side as the trigger, old active on pump side between relay and pump (accessory), and earthed it using 30cm of 4mm wire. Car starts and runs fine, but when I switch it off the engine continues running and there is 8v in the trigger wire at the relay.

So basically the relay is not switching to off position as far as I can tell. I've replaced the relay so I'm confident the relay isn't faulty. Where have I gone wrong??

Thanks.

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https://www.sau.com.au/forums/topic/477614-fuel-pump-direct-wire-mod-issues/
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GTSBoy Grand Master

GTSBoy

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Posted

You have wired it wrong. Get the wiring diagram (for just about any similar RB engined car). The R34 one will do. Look at the wiring for that circuit. It appears next to the ECU pinout. You will see that the ECU provides the earth for the fuel pump on 2 terminals. One with the resistor to drop the pump voltage, one without and controlled by the original relay. The 12V+ battery to run all this comes from outside all of this lot. If you wire it up wrong you can be putting the new 12V+ onto the back side of the resistor and giving some voltage to each of the ECU and the fuel pump - keeping it running. You have to make sure that your new wiring does things in the same order as the original wiring, and make whatever disconnections you need to. You just need the ECU to provide the constant earth (not through the resistor) to make the new relay pull in.

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