HFS-3 'box/control unit' sending voltage out the green wire, HELP.

[The Alchemist]

So I have a HFS-3 unit from Howerton and it's been on my 2000 trans am for a couple years now. After this winters rebuild to a bigger motor and bigger blower, I've recently been chasing a P0200 code, which is injector malfunction.

Long story short, I checked all the voltage at the injector connectors and found 10-11v on the #1 signal wire with key on/engine off. I traced it back to the pcm, and found the Aquamist green wire is tapped to that injector signal wire. So I removed the green Aquamist wire, and sure enough, it has voltage going to it. I checked the continuity and it checked out fine. Next I disconnected that harness from the controller box and checked again, and there is no voltage. Checked the box itself, and sure enough, it is sending the voltage to the green wire.

I'm guessing the controller box is bad and I need to have it repaired.

Any help is appreciated.

Thanks.

[Richard L]

I think you are reading too much into this. Plug in the fuel injector and remeasure the same point (injector(-)), with and without the green connector plugged into the H3 controller.

Let me know.

Richard

[The Alchemist]

I did as you asked, and with the connector plugged into the H3 controller, I see ~10.1v with Key on, engine off, the positive side was 11.5v. Then I unplugged the connector from the H3 controller, and I see 0v.

http://www.aquamist.co.uk/vbulletin/attachment.php?attachmentid=360&stc=1&d=1436116513

[The Alchemist]

Am I looking at this wrong?

[Richard L]

you must re-connect the fuel injector back to the plug and then measure.

[The Alchemist]

So you're saying that it is normal for the controller to send ~10-12v through that wire? If so, then I won't worry about it. I was chasing an injector malfunction error code and wanted to make certain it wasn't coming from the Aquamist setup.

[Richard L]

It is normal for the controller to send out a voltage to the injector(-) to set the logic state. When the ECU pulls this voltage down, the controller will calculate the duration and works out idc%.

The current of the pull-up voltage is about 5mA, compared to the 800mA of the fuel injector, almost insignificant. For low impedance injectors, it is around 4,000mA.

Compare the impedance of your new fuel injector to the previous, you might make more progress.

[The Alchemist]

Thank you Richard for you detailed response, I appreciate it. I'm not an electrical expert, chemistry is more my thing, but do understand what you are saying. I was chasing a P0200 code, which is injector malfunction error, but it didn't tell me which injector. So when I started checking voltage at each injector, and saw the voltage at number 1 injector and traced it back to the Aquamist controller, it got me questioning if it was supposed to be there.

In the end, it was my injector harness adapters that were causing an issue. New pigtails soldered in and everything is fine.

Thank you again for your help and explanation. I plugged back in the Aquamist last night and the car is running great.

[Richard L]

Not a problem, I am glad you have tracked down your problem.