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hard wiring fuel pump


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Hi all,



I recently bought Aeromotive 340 fuel pump and it was running fine until my EFI relay melted. I was told I need to run a 10 gauge and hard wire it directly to the battery.



So I ran eh wire directly from the battery to a relay then to the positive side of the pump then run ground wires as well. Now I'm not sure where to tap the switch from the relay to activate the pump. I was thinking to tap it on the ECU but where?



Right now, I just tapped it on the ignition so when the key is on 'ON' position, fuel pump primes but I heard this is unsafe specially when crashing your car.



Can I still use the OEM relay to use a relay switch? I don't wanna put a kill switch to retain the "OEM-ness" of the harness.



Car is ae101 using 2nd gen 4efte (not green label) by the way if that's an issue. All wirings have no problem initially until I changed the pump

Edited by boosted.rolla
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Common conversion on the evo but i would guess you will need a relay in your citcuit

A small kill switch placed neetly somewhere wouldnt do no harm and its safety

Yeah I did add a relay but I don't wanna add a kill switch.

Just use the original 12v feed to the fuel pump to activate the relay

You mean the feed that comes from the ECU? Is it safe to use? Wouldn't I melt anything or do I need to upgrade this wire as well?

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^^^ no as your using it just as a signal to ope relay clever thinking richard

Got it. To be clear since I'm away from the car right now and can't remember what wire I used before, which wire I should use from the ECU? I believe I used something from Connector 2.

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okay guys I'm now confused. Hardwiring it directly to the battery and ignition makes the car unsafe specially when crashing but I thought thats how it was wired on stock except using a smaller gauge wire.

Care to enligthen this one? How should I wire my pump to make it safe?

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no stock ecu wire triggers the feul relay ( low power ) the relay sends bigger power amps always use a relay



use the same wire from ecu to power up any other relay you want !!! ( still works like stock ) fit a thicker gauge wire from your new relay and run that to the back pump



or as richard mentioned firts by using the original wire on pump as a trigger for your new relay circuit setup



http://www.enginebasics.com/Advanced%20Engine%20Tuning/fuel%20pump%20relay.html



""""" the red feulpump power wire """" in that diagraw will be your signal wire from ecu you get the idea now you can tap this setup of after any other 1 if you get me


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If going to be using a standard automotive bosch relay and assuming you have fixed the original setup which then its pretty easy to wire up. Basically use the original feed wire to trigger the new relay - there wont be any load on the original wiring/circuit open relay that way.



On the normally open relay the terminals are labled:


30 - Load feed ie fused supply from the battery, large capacity wire


85 - 12v Trigger, use the existing 12v fuel pump feed


86 - Ground


87 - 12v Output to fuel pump



Or if you wanted to forgo the factory circuit open relay you can wire it:


30 - Load feed ie fused supply from the battery, large capacity wire


85 - 12v feed from ignition key when "ON"


86 - Trigger, use the FC pin from the ecu which is a ground trigger


87 - 12v Output to fuel pump



Looks like those pumps can pull up to 20amps so make sure your using appropriately sized cable for the lengths you need.


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Thanks guys!



But do you usually hard-wire your fuel pump? I haven't seen a starlet (or at least on a 4e engine swap) did this before, so I'm quite curious that probably there's a wiring problem on my system currently that's why it melted aside from the pump can pull 20 amps.



Is it possible that my fuel pressure changed when I upgraded my fuel pump causing it to pull higher amperage than normal?


Edited by boosted.rolla
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Usually the standard circuit open relay is fine to run the pump, I'd guess there might be a poor earth or short somewhere that caused the issue.



I wire up alot of ecu's and generally still use the factory relay setup and just use the aftermarket ecu to trigger it. I only usually change the relay setup where its a more serious setup with a need for higher voltage or greater current capacity to the pump. Even with the alternator charging at say 14v the fuel pump can sometimes be only seeing 12-12.5v via the stock wiring.


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