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Location:
Pine Rivers QLD
Registered:
April 2005
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fuel pump stuff
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Sun, 24 July 2005 05:13
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i need to know if you can wire a stock fuel pump to 12V's via a relay. i know that some fuel pumps run 2 voltages to run the pump slower during idle. is it bad to wire one of these pumps directly to 12V's? or will it help improve the air fuel mixtures during boost ect?
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Location:
Montrose, VIC
Registered:
May 2002
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Re: fuel pump stuff
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Sun, 24 July 2005 10:19
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Most pumps will be alright with it... What car/engine/pump?
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Location:
Forrestdale W.A.
Registered:
October 2004
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Re: fuel pump stuff
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Sun, 24 July 2005 10:31
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You have an injected car? It will have a pressure regulator on the fuel rail which allows excess fuel to go back to tank. My advice is wire it to 12v and let the fuel pressure regulator do the rest. I believe that most pumps are designed to work this way as the fuel that flows around the motor also keeps it cool
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Location:
Brisbane
Registered:
May 2002
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Re: fuel pump stuff
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Mon, 25 July 2005 00:41
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Some factory fuel pumps are wired up in a 2-stage fashion, ie lower voltage when the engine is at low load. This is only done to reduce noise at low speed. Hooking it up to constant 12v will be fine, the only downside will be a little more noise. 
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Location:
Pilbara
Registered:
November 2004
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Re: fuel pump stuff
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Mon, 25 July 2005 01:21
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I could be wrong but I believe it's illegal to hook up a fuel pump straight to the ignition (constant 12 volt). The only way to do it safely and legally is through a circuit open relay. If you crash and the fuel is connected to constant 12 volt it could mean spraying fuel everywhere resulting in fire.
Not to worry though as I have put cars up for roadworthies and passed them with the pump connected to the ignition...
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Location:
Brisbane
Registered:
May 2002
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Re: fuel pump stuff
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Mon, 25 July 2005 02:29
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WTF? No-one is talking about hooking up the pump to the ignition. 
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Location:
Pilbara
Registered:
November 2004
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Re: fuel pump stuff
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Mon, 25 July 2005 04:25
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is it bad to wire one of these pumps directly to 12V's?
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WTF? No-one is talking about hooking up the pump to the ignition.
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My understanding is that he is asking if it's ok to wire the pumps directly to 12 volts. You are right, no one has talked about wiring to the ignition , my mistake.
Regardless, it's best to wire pumps through a relay.
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Location:
Pine Rivers QLD
Registered:
April 2005
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Re: fuel pump stuff
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Mon, 25 July 2005 09:30
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yeah i was thinking one of those missile switches for the fuel pump lol. The main problem i was having here was the fact that i couldn't find the fuel pump relay (that switches from high to low). But it turns out after tracing wires that i don't have one!!!! and i hadn't wired the opening relay properly (as there is two triggers for it) so thanks for you help but its running how it was meant to not without me doing the dodgy.
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Location:
Pilbara
Registered:
November 2004
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Re: fuel pump stuff
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Tue, 26 July 2005 01:03
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The circuit open relay is the one you want to operate the fuel pump, it is the fuel pump relay. Standard deal is that your circuit open relay will operate the pump/s when it cranks over from input from the starter circuit and then once the motor is going the AFM supplies input operating the pump on a high/low feed basis.
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