Fuel pump hot wire
Sep 23, 2008, 05:24 PM
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Fuel pump hot wire
Ok, I search for about 1 hour but didnt find a good enough answer, nor a thread from the last 2 years on the subject. 
I recently did a fuel pump hot wire, ran a 8 gauge power wire to a relay, then to the pump using the factory power supply wire for the remote switch for the relay. I also used a 8 gauge ground wire for the relay, tieing it into the factory ground for the pump. (always taught if upgrading the power wire, the ground must be the same gauge as the power)
Well anyways, the car runs fine and dandy. Getting 14.4+volts at idle and all, where as it was getting 7.8v. also have seen about .2-.5 decrease in a/f ratio (richened up) so I went for a few logs. Sent the logs off to TouringBubble (my tuner) and he says that the logs seems to be showing the car is now LEANER than before, not alot leaner though. Edit-running .3 AFR leaner at WOT and +3% or so in the fuel trims
Any Ideas why? Did I use the wrong remote wire for the relay to switch the relay on? (factory voltage drop affecting the relay, not allowing full power to pump at higher loads)
***diagrams added***
Factory wiring
My current howiring
The way my Mitsu Tech suggested to wire
I recently did a fuel pump hot wire, ran a 8 gauge power wire to a relay, then to the pump using the factory power supply wire for the remote switch for the relay. I also used a 8 gauge ground wire for the relay, tieing it into the factory ground for the pump. (always taught if upgrading the power wire, the ground must be the same gauge as the power)
Well anyways, the car runs fine and dandy. Getting 14.4+volts at idle and all, where as it was getting 7.8v. also have seen about .2-.5 decrease in a/f ratio (richened up) so I went for a few logs. Sent the logs off to TouringBubble (my tuner) and he says that the logs seems to be showing the car is now LEANER than before, not alot leaner though. Edit-running .3 AFR leaner at WOT and +3% or so in the fuel trims
Any Ideas why? Did I use the wrong remote wire for the relay to switch the relay on? (factory voltage drop affecting the relay, not allowing full power to pump at higher loads)
***diagrams added***
Factory wiring
My current howiring
The way my Mitsu Tech suggested to wire
Last edited by sabastian458; Sep 25, 2008 at 09:03 AM.
Sep 23, 2008, 05:27 PM
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Cliff notes: ran 10 gauge wire to fuel pump for power, ran 10 gauge wire to pump for ground, Used relay for switching for pump by ignition switch. Vehicle now running leaner where it should be running richer.
Sep 24, 2008, 01:09 PM
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wow, seriously. No help?
This is what I have come up with so far. The first pic is of the factory fuel pump wiring. The second is what I am currently running.
pix moved to post 1
This is what I have come up with so far. The first pic is of the factory fuel pump wiring. The second is what I am currently running.
pix moved to post 1
Last edited by sabastian458; Sep 25, 2008 at 06:30 AM.
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Sep 25, 2008, 10:03 AM
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Is your tune that tight on the car that you never have a variance such as .3 points of AFR if ambient conditions change? I don't think you've done anything wrong and I would just retune and forget about it.
You aren't going to really see any difference in performance by supplying more voltage to the pump unless you were previously having a pressure drop problem due to it being out of flow or insufficient voltage.
You aren't going to really see any difference in performance by supplying more voltage to the pump unless you were previously having a pressure drop problem due to it being out of flow or insufficient voltage.
Sep 25, 2008, 10:06 AM
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well, with the factory wiring it supplys 7-8volts to the pump under light load and 10-11 under load. by doing the hotwiring, it is suppose to supply direct battery voltage to the pump causing it to pump more (supply more in theroy i guess)
I did some logs before during the day, then did the hotwire and compairing both logs, the car went leaner. the only change being the hotwire.
I did some logs before during the day, then did the hotwire and compairing both logs, the car went leaner. the only change being the hotwire.