2nd Fuel Pump Control

[EricM]

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.

 

[EricM]

If you want to PWM (pulse width modulated speed control) that 2nd pump (usually not necessary), instead of on/off. Then instead of the Programmable On/Off Out, use the Generic PWM outputs, see picture. You may have to play around with the duty cycles to get the effect you want. This table was set up for the main fuel pump. This is more difficult to set up and requires a solid state relay (see article on fuel pump speed control).

 

[EricM]

Updated some info, reworded some things.

 

[turbobuick]

Is hysteresis just a 20kpa area below 200kpa that the pump won't turn on and off if boost is fluctuating around 200kpa or is it a set point at which the pump will shut back off and is that set point 180kpa?

 

[EricM]

Yes it should come on at 200, then back off at 180, so you don't get any rapid on/off if the boost floats around in that area.

 

[Justintt]

Eric
I was considering using Terminal Strip #7, "High Current Out 3" to trigger a relay for the second fuel pump. Is this OK to do and does that terminal output ground or power?

 

[EricM]

Yes terminal 7 will work. It's a grounding output.

 

[Justintt]

Thank you Eric, I read and re-read the documentation and thought that it was a grounding output, but the terminal name made me question myself.

Is there a way to test the functionality of the second pump trigger when the car is not running?

 

[EricM]

With the laptop connected, go to the Testmodes menu, then "Output test mode I/O". Press "enable test mode", then press the On button for whatever output you want to test. In this picture, fuel pump is circled.

 

[Turbo 6]

When tying into the purge canister connector, does it matter which way the wires go?

 

[EricM]

No, in this case, you are just activating the coil on the relay, so the 12v and ecu signal can go either way.

 

[Turbo 6]

When trying to test the 2nd pump through the way you posted, do I turn on injJ?

 

[EricM]

Yes if you’re testing Inj J output, then turn on Inj J.

 

[Turbo 6]

Connected into the purge canister harness and set inj j up in to come on at 200kpa (as in the example). Went to test run the pump in the test mode turning on inj j and nothing. I did try the Hobbs switch applying pressure and still nothing. If I put the jumper in, the pump runs. This is on the new racetronix dual pump harness, btw.
Also, tunerstudio was stating that I had already had the stepper on output 1. I had to turn that off in order to clear the error. I don’t remember if that was turned on or off. Is that needed?

 

[EricM]

In the directions I posted at the beginning, I presented 2 options of controlling the 2nd pump. One is through a mechanical (on/off) relay, and the other is using a solid state relay to pulsewidth modulate (pwm) the pump (not common).

Which one are you using? It sounds like you turned on both of them.

 

[Turbo 6]

Yeah at some point I must have turned on the stepper. Just want to make sure I don’t need that on for any other reason.
You did post about the relay. I completely forgot about that. That’s the way I plan on activating the 2nd pump. I’ll proceed according to your post.

 

[EricM]

Ok, start there, and let me know how it goes, or if you have questions.