Fuel Pump Relay

Quik95SC

SCCoA Member
Does anyone have a digram of how they used a relay to get a full 12V back to the fuel pump harness. I am wanting to do this as well, but not quite sure how to wire in the relay to get it to only come on when ignition is on.

I understand you run a 10 gauge wire from Alternator connection to the fuel pump, but exactly which wire do you connect to on the fuel pump harness and how would I wire it with the relay so it will only come on while ignition is on?

Thanks,

Smitty
 
Use the existing fuel pump power wire to trigger the coil of the relay. Run the heavy gauge wiring from the battery, through a fuse, through the relay normally open contact to the pump. You can ground the other side of the relay coil right on the mounting screw for the relay.
 
I dont remember which wire going to the fuel pump was 12V key controlled. I pulled the plug off the top of the fuel pump and used a 12V tester and figured out which pin was hot with the key on and used the wire providing it power to run the relay. I hooked directly to the battery since I have the battery in the trunk and much closer than the alternator. I also checked the power coming into the pump prior to switching and it was providing something like 9.7V to the pump. after the harness install the power going to the pump was above 13V.

Ken
 
I can get you a wire diagram tonite with the relay lug numbers, since mines easily accessable under the back seat. I also cut the fuel pump ground wire and located it on a new relay ground and the KB BAP ground, since the harness ground goes all the way up to the driver side kick panel.
 
Use the existing fuel pump power wire to trigger the coil of the relay. Run the heavy gauge wiring from the battery, through a fuse, through the relay normally open contact to the pump. You can ground the other side of the relay coil right on the mounting screw for the relay.

Yeah this makes sense. After I posted this I got to thinking about it and had this same idea, this just helped verify what I was thinking.

Any regular 30 Amp relay should be fine correct?, with the normal 30,87,87a, 85,86 contact numbers on it.

I have a pretty bad Trans Front seal leak, so I will be tackling this job after this weekend, and figured while I had the tranny out and tank down, I would do this fix as well.

Thanks,
Smitty
 
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I dont remember which wire going to the fuel pump was 12V key controlled. I also checked the power coming into the pump prior to switching and it was providing something like 9.7V to the pump. after the harness install the power going to the pump was above 13V.

Ken

Wow only 9.7 Volts, :eek: man is that low! I will measure mine for sure and see what it is?? ;) Good tip right there to compare the 2.

Silly me I have the EVTM's, so figuring out the wiring is realy the easy part, but yeah I could do the same and use my test light to figure out the hot wire while ign is on.

Smitty
 
jUST MAKE SURE YOU USE THE FUEL PUMP WIRE after the inertia switch to trigger the relay, incase you have an accident it will kill the pump.
 
Oh yeah

jUST MAKE SURE YOU USE THE FUEL PUMP WIRE after the inertia switch to trigger the relay, incase you have an accident it will kill the pump.

Great point, but does the fuel pump have more than one 12v ign wire in the connector, or does it only get it after it goes through the inertia switch?

Thats easily verified, but unplugging the inertia switch and see if I loose the 12V on the pin.

Good tip!!

Smitty
 
It goes thru the inertia switch then to the pump.As long as you pull the wire from the trunk area you should be good. But you can easily test it like you said. Or hit the inertia switch so the button pops up and check voltage or hit it while its running and see if the car dies.
 
You'll want to splice in the power wire the closest to the pump you can get, pull the back seat and access the harness there. If you do it there you'll have no problem worrying about the inertia switch. I spliced mine before the connector that runs directly to the fuel tank thats under the car, you can pull it up thru the back seat grommet so you don't have to drop the tank.
 
Very Cool

You'll want to splice in the power wire the closest to the pump you can get, pull the back seat and access the harness there. If you do it there you'll have no problem worrying about the inertia switch. I spliced mine before the connector that runs directly to the fuel tank thats under the car, you can pull it up thru the back seat grommet so you don't have to drop the tank.

Didn't know the harness went under the rear seat, that will be so much easier.

Is it the only harness near the center of the seat bottom, so it is easy to find? Should have 4 wires correct? :confused: Power, ground, fuel level sensor, level sensor return?

Where did you put the relay, just secure it under the back seat somewhere? Or does it fit through the hole down towards the fuel tank with the connector and replace grommet afterwards?

Great help guys, thanks. I may get this done before I go to KY this weekend!! Well tonight or tomorrow night it looks like!

Smitty
 
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