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Old 12-03-2011, 05:28 PM   #1 (permalink)
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***Fuel Injector Kill Switch Wire Question***

I'd like to wire in a switch that will immediately kill power to the injectors.

1990 CRX HF:
Does anyone know what wire would be best to cut for an injector kill switch?

Photos show my "PGM-FI Main Relay"




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~Jason

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Old 12-03-2011, 09:20 PM   #2 (permalink)
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I put a FI kill switch in my '97 but I got to the needed wire under the hood.

But here's a thought, to help ID the wire on your relay connector there.

Examine the wires at the fuel injectors. 2 wires at each, and one of those is the same color at each injector. That is the 12V power wire. I think on my car they are yellow with a black stripe?? But you'll have to see it on yours.

The other injector wire is a different color at each injector, and that is the ground. The ground is the side of the circuit that the computer switches on/off to control injector pulses. That's why each one has it's own distinct ground wire. The 12V + wire is always powered when the engine is running.

Anyway, now you know what color is the injector +12V wire. Now find it at the relay. It splits to four wires later, but I think the color is the same. I'm pretty sure the system powers that wire ONLY when the engine is turning (including when starting cranking), and for a couple seconds after you first turn on the key - just to pressurize the system. So if you have a voltmeter, you can test to verify you have the right wire at the relay.

Good luck with it - it's a great mod to have on a FE car.
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Old 12-04-2011, 09:38 AM   #3 (permalink)
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That's the best reply out of 3 sites: Thank you!

I just came across this. I'm only interested in killing power to the injectors. I need to keep my lights, signals and gauges. I want power killed to the injectors immediately...I don't want a kill switch to the fuel pump...I don't think...



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Old 12-04-2011, 10:17 AM   #4 (permalink)
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Quote:
Originally Posted by brucepick View Post
...
Examine the wires at the fuel injectors. 2 wires at each, and one of those is the same color at each injector. That is the 12V power wire. I think on my car they are yellow with a black stripe?? But you'll have to see it on yours.

The other injector wire is a different color at each injector, and that is the ground. The ground is the side of the circuit that the computer switches on/off to control injector pulses. That's why each one has it's own distinct ground wire. The 12V + wire is always powered when the engine is running.

Anyway, now you know what color is the injector +12V wire...
Well I don't believe this will work. There is a red wire in some sort of configuration at each injector, but each red wire has a different color stripe. The remaining wire at each injector is either yellow, white or blue each with a different colored stripe. This is nuts...wiring always causes me fits!
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Old 12-04-2011, 12:00 PM   #5 (permalink)
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just cut the PGM FI relays ground. Engine dies immediately. As soon as the ground is restored all turns back to normal, and a bump-start will fire you right back up. The temprary disruption to the fuel pump is not an issue. Use a push to open momentary then all you need to do is hold it while the engine dies. See my write up for a 5th gen civic your 4th gen will be quite similar.
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Old 12-04-2011, 01:38 PM   #6 (permalink)
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Do I really want to cut the ground to the PGM FI relay?

Again I don't want to lose my instrumentation, lights, turn signals...

I appreciate the help guys...I'm trying to get this lined out today so I can drive it to work tomorrow.

~Jason
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Old 12-04-2011, 06:19 PM   #7 (permalink)
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Quote:
Originally Posted by jasonst View Post
Again I don't want to lose my instrumentation, lights, turn signals...
Bestclimb has it. Cut the ground. That is what I did in my 1998 Civic. I do not lose lights, signals, speedo... radio... you name it and I'll tell you it still functions. What will happen is my UG will cut out sometimes, especially if I keep the switch off for an instant too long. But since it keep calculating, I believe the ECU has not cut out. Here is the build thread on my project.

Good luck.

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Old 12-04-2011, 07:57 PM   #8 (permalink)
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Only thing you loose is the tach, but the engine is off so that hardly matters. Close the switch again and tach comes back.
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Old 12-05-2011, 12:17 PM   #9 (permalink)
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Thumbs up Alright...I'm doing it.

I appreciate the help from you all. I'll try to get this done after work.

I'll take pictures and complete a write up when I'm done.

Thank you again,
~Jason
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Old 12-05-2011, 11:39 PM   #10 (permalink)
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writeup

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