Fuel pump wiring question

David Neibert

SCCoA Admin
I just received my Kenne Bell boost-a-pump (fuel pump voltage regulator/increaser) and now I'm looking for the best place to mount the module and best location to acess the power wire that goes to the fuel pump.

I know I could get to the power wire by going under the car to make the splice, but would rather do it in the trunk in the location of the fuel cutoff switch and pump relay. Does anyone have a diagram showing which of those wires supplies the power to the pump ? I would like to tap into power supply wire after the relay and before the pump, and mount the module in the trunk or under the rear seat.

The voltage control knob will be mounted in my console or the glove compartment.

David
 
David,

You could either splice in at the inertia switch in the trunk, or where the wires go to the pump/sending unit under the passenger side of the rear seat (inside the car).

At the inertia switch, the red wire is 12V power from the main connection under the driverside dash, and the white wire supplies power from the inertia switch to the fuel pump relay. From the fuel pump relay, the pink wire with the black stripe supplies 12V power to the fuel pump.

-Rod
 
Dave, i ran my own dedicated circuit with relay and 10 gauge wiring. The difference was huge. i left the stock wiring and added the new circuit with a switch. that way you could start the car as normal, or turn it on manually. I think that it alone would be enough to feed for the nitrous. I think the voltage difference between the two was 1.5 volts. I can actually hear a huge difference. just something for everyone to think about
 
I see one potential problem with tapping into the pink/black wire at the fuel pump relay since this wire runs to the fuel pump and to the EEC (pin 8 – Fuel Pump Monitor signal). I may be completely wrong on this, but I thought it worth mentioning. My knowledge of the Kenne Bell boost-a-pump is minimal as I heard about it only today. I’m guessing that it raises the voltage supplied to it, then regulates the voltage, and finally runs the pump based on the driver-operated voltage control knob. If something went wrong with the boost-a-pump's voltage regulator circuit, and if it doesn't have a voltage limiter at its output or the limiter failed, the EEC would be hit with a voltage that's higher than the boost-a-pump's working max output of 17.5 volts. If this scenario is possible, then it would be preferable to cut the pink/black wire only after it branches off to the pump.
 
Stay with me on this David. I would
1) run a seperate wire #10 as Kevin said.
2) put it in the trunk
3) run a relay so when the fuel pump kicks on, the inetia switch powers up the pump but no voltage is lost through it and it does not matter which wire you splice into because they are both power when its workin.
4) put a switch in the cabin that cuts the power to it. This way if it funks up somehow (like it seems to plague some of your projects) you can still cut it off before the car is a total loss.

That is how I would run it anyway:)

Chris
 
seawalkersee said:
Stay with me on this David. I would
1) run a seperate wire #10 as Kevin said.
2) put it in the trunk
3) run a relay so when the fuel pump kicks on, the inetia switch powers up the pump but no voltage is lost through it and it does not matter which wire you splice into because they are both power when its workin.
4) put a switch in the cabin that cuts the power to it. This way if it funks up somehow (like it seems to plague some of your projects) you can still cut it off before the car is a total loss.

That is how I would run it anyway:)

Chris

I could run a new circut directly from battery power using 10 gauge wire and install a relay under the rear seat and use the existing fuel pump power wire to trip the relay. That way the inertia switch still works and the EEC is still controlling when the pump starts and stops. That is exactly what we did on the turbo car, but it's a little more work than I really wanted to do because it requires dropping the fuel tank to upgrade the wire all the way up to the connection on top of the fuel tank.

Please keep in mind that I will only be using extra voltage when the nitrous is used, which only happens a couple times a year at the track. The rest of the time the voltage will be turned down to the minimum setting.

David
 
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The fuel pump splice was why I would suggest the pigtail on the inertia switch. If you run the ground or power from the pigtail to the relay, you will still have the switch in working form. Also...no need to drop the tank:)

Chris
 
J.D. said:
I see one potential problem with tapping into the pink/black wire at the fuel pump relay since this wire runs to the fuel pump and to the EEC (pin 8 – Fuel Pump Monitor signal). I may be completely wrong on this, but I thought it worth mentioning. My knowledge of the Kenne Bell boost-a-pump is minimal as I heard about it only today. I’m guessing that it raises the voltage supplied to it, then regulates the voltage, and finally runs the pump based on the driver-operated voltage control knob. If something went wrong with the boost-a-pump's voltage regulator circuit, and if it doesn't have a voltage limiter at its output or the limiter failed, the EEC would be hit with a voltage that's higher than the boost-a-pump's working max output of 17.5 volts. If this scenario is possible, then it would be preferable to cut the pink/black wire only after it branches off to the pump.

As you suggested Kenne Bell's instruction also say to splice into the fuel pump voltage supply wire after the wire going to the EEC, so that the EEC doesn't see the increased voltage and throw a check engine light.

Does anyone know exactly where this wire branches off on a 91 SC ? Hope it's in the trunk and not under the car.

BTW, the system I bought works off manifold pressure. There is a pressure switch preset to 5 psi that must be tripped to enable the system. Then there is a dial to adjust additional voltage from 0 to 50%. I plan to leave it set to 0% except when using nitrous, then I'll turn it up to whatever voltage I find is needed by testing the nitrous system on the dyno. Since I'm not comfortable going any higher than 500 rwhp I'm only planning to use a 75 HP shot of nitrous.

David
 
David Neibert said:
................
Does anyone know exactly where this wire branches off on a 91 SC ? Hope it's in the trunk and not under the car. ..................
David
According to the EVTM, the splice is at the "Window regulator jumper harness, below LH door sill, near T/O to G300 ground bus".
 
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