For a double pumper style fuel setup, you can activate the 2nd fuel pump using the ECU instead of the hobbs switch. You will need a relay to control it. The relay needs to be rated for the max current of your pump. (if you have a double pumper harness, you likely already have the relay)
A typical automotive relay will have numbered terminals on it. 85, 86 are used to activate the relay. 30, 87 send power to the pump. There is also 87a, but don't wire anything to that.
The control (coil) side of the relay, terminal 85, will have ignition switched 12v, and the ground, terminal 86, will go to an output of the ECU. When the ECU activates the output, it grounds it, which turns it on. This wire doesn't have to be heavy gauge as it doesn't require much current.
Terminal 30 at the relay needs 12v power that will go to the pump through terminal 87 when the relay activates. This wire needs to be heavy enough to support the current draw, normally 10 gauge. The 12v power to terminal 30 normally comes from the alternator or battery. Terminal 87 then goes to the pump (same 10 gauge wiring).
At the ECU, a common extra output to use, since it's under the hood, is the old canister purge solenoid (which goes to terminal A3 at the old ECU connector and is green/yellow in color). This is known as Injector J in the software (INJ J). This where terminal 86 of the relay would get wired to.
Here's how to set up that output in the software.
Go to the Advanced Engine menu, then Programmable On/Off Outputs 1.
Scroll down to Injector Out J (as an example), enable it, and set it up like this pic. I have it set to come on when MAP exceeds 200kpa (about 15psi boost). And it will turn off if the MAP goes 20 below 200kpa. You may need to experiment with that 200kpa setting for your car.
A typical automotive relay will have numbered terminals on it. 85, 86 are used to activate the relay. 30, 87 send power to the pump. There is also 87a, but don't wire anything to that.
The control (coil) side of the relay, terminal 85, will have ignition switched 12v, and the ground, terminal 86, will go to an output of the ECU. When the ECU activates the output, it grounds it, which turns it on. This wire doesn't have to be heavy gauge as it doesn't require much current.
Terminal 30 at the relay needs 12v power that will go to the pump through terminal 87 when the relay activates. This wire needs to be heavy enough to support the current draw, normally 10 gauge. The 12v power to terminal 30 normally comes from the alternator or battery. Terminal 87 then goes to the pump (same 10 gauge wiring).
At the ECU, a common extra output to use, since it's under the hood, is the old canister purge solenoid (which goes to terminal A3 at the old ECU connector and is green/yellow in color). This is known as Injector J in the software (INJ J). This where terminal 86 of the relay would get wired to.
Here's how to set up that output in the software.
Go to the Advanced Engine menu, then Programmable On/Off Outputs 1.
Scroll down to Injector Out J (as an example), enable it, and set it up like this pic. I have it set to come on when MAP exceeds 200kpa (about 15psi boost). And it will turn off if the MAP goes 20 below 200kpa. You may need to experiment with that 200kpa setting for your car.
Last edited: