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Old 10-06-2011, 07:35 AM   #9 (permalink)
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Originally Posted by PaleMelanesian View Post
I'm not quite following the actual wiring details here. Are you breaking the black (ground?) wire or are you grounding out something?
I just did a careful read of the link given in this thread's first post.
Both methods use the new switch to temporarily sever the black (ground) wire that goes to the injector relay.

You sever the black wire and insert the switch into the cut location. California98Civic specifies an interrupter switch, also called "NC" type. Normally Closed. Which means that it is normally "on" when not pressing the button.

Here's a bit more electrical detail, if you would like to understand what's happening.

The relay has a "switched" side (or power side) and a "control" side. Two wires for each side, total of four wires. The switched side has a powered lead going in, a small internal switch, and the lead going out to the injectors. The internal switch controls whether that power is sent out to the injectors.

The relay's control side has its own powered lead going in, which powers a small coil that activates the switch. And there's a ground going out from the coil that completes the coil circuit. As long as there is power to the coil and a ground path out of the coil, the internal switch is closed ("on"), and the relay's switched side sends the switched power out to the injectors.

By temporarily severing the ground wire you disable the relay's internal switch, and it sends out no current from the switched side.

Normally the car's computer controls the relay to enable or disable the injectors. This modification just adds one more place from where the relay's status can be controlled. I can't tell from here whether the computer switches the power to the relay's control side on and off, or whether it severs the control side's ground, basically like this mod does. Either way would disable the small coil, which ultimately means no power going out to the injectors.

The injectors themselves receive constant power as supplied via this relay. They are controlled on their ground side. Each injector has its own ground wire going to the computer. The individual grounds are completed by the computer for small fractions of a second at a time. Each injector will squirt fuel only when its individual ground path is completed by the computer.

Sorry for all the wordage. I'm the only one awake in the house and it's too early to do other things.
Coast long and prosper.
Driving '00 Honda Insight, acquired Feb 2016.

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