#172CR

Hi,

I'm going to install a fuel pump kill switch but I was hoping to get some information on wiring and generally how to do it. I've searched but couldn't find anything that really told me how to do it. Is there a "How To" guide that I missed somewhere??

Thanks for your time

Neutered Sputniks

It should be relatively simple. You'll need to know which wire is power to the pump (or the "turn on" signal if there is one, not sure). You'll cut this wire, and insert a relay (contact pins). One coil pin off the relay will go directly to a ground point on the chassis, the other coil pin will go to one side of your switch. The other side of the switch will be wired to your battery positive terminal.

Thus, when you flip your switch to "on," the current flows from the battery, through the closed contacts of your switch through the coil of the relay (activating the coil) and then to ground. The activated coil will cause the relay to switch to closed, allowing the fuel pump power to be sent through the relay contacts and to the pump.

Make sense?

#172CR

Yeah it makes sense, I was planning on integrating it to a current switch on the car, I just didn't know where the fuel pump wires ran from. I guess they'd be coming out of the ECU wouldn't they? My next plan of action would be a wiring diagram of the ECU?

Neutered Sputniks

I would trace the wires back from the fuel pump (contained in the tank, I believe). Not sure where they come off the ECU at. If it were me installing the cutoff switch, I'd probably put the relay in the bulkhead behind the driverseat - not easy to get to for a thief to bypass, but where the fuel pump wires run through anyway so easy enough to install.

FoodeesJim

I agree with Neutered as far as security is concerned. However, I would install your relay in a location that is well concealed yet still accessible by you in the event the relay fails in some way. Believe me, relays do fail and it would suck to be stranded somewhere and unable to perform an easy fix...

#172CR

That's great information both of you guys. Learning all of this stuff has been fun, but finding out how easy our cars are to steal has also made me weary. I had an SI prior to my S and I took so much apart to learn where lines were and how things ran, but I really don't want to mess anything up on this.

To trace the wires back from the pump; would I have to remove the seats and plastic paneling behind the seats/console to get to the wires, or would I have to go from under the car to trace the wiring back??

Neutered Sputniks

You should be able to trace them back right off the tank in the trunk area, I believe the wires run inside the cabin, so you'll have to at least take off the side piece (which means pulling off the vented piece in the middle.

Just keep a screwdriver in the car in case the relay goes out...and hide the switch somewhere very VERY inconspicuous.

#172CR

Sounds good, again great info. What are the potential negatives if the relay goes out?

Also, I was wondering, if I just use a manual switch, like the switch that locks the power windows for instance, would I still need a relay if I have it pass through that?

Neutered Sputniks

The benefit of the relay is that it's remote. Otherwise, you're diverting power for the fuel pump to where you mount the switch.

If the relay goes out it will either remain closed (fuel pump cannot be switched off with your switch) or open (fuel pump does not turn on). In all the years of using automotive relays for off-road lighting on my truck, I've never had one go bad.

2big4aS2000

i would not worry to much about a relay going bad, just buy a good quality relay, depend on mods to your car, i have on several turbo and sc cars run a 8guage power and ground wire to the fuel pump, used the factory wire to trigger a relay, i saw a 1 volt increase to the fuel pump under heavy loads (20lbs boost at red line, making 505hp on stock motor) fuel pressure never dropped!, you could do this up grade and put the switch between the relay and factory wire, you could use the cigarett lighter as a switch, take it with you and car would not start