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Old 09-10-2008, 12:26 PM   #7 (permalink)
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Originally Posted by Gregte View Post
I did it on my GMC sonoma 4 cyl. by finding the correct wire on the ECM under the dash. You can just use one of the two wires of any fuel injector. One of them will be hot when the engine is running and the other will be switched, i.e. pulled to ground by the controller. It will be a square wave with a varying duty cycle that varies depending on how much fuel is being asked for. It will not be a varying voltage in the direct sense but can easily be turned into a varying voltage for feeding to a comparator or anything else you wish to do with it.
I was hoping to patch in right at the injector, since it is much more accessible on my cars than is the controller. However, I have not had any success in locating a test "tap", that could be plugged in between the cable and the injector. There are places that sell the "cable" side connector, but nobody seems to carry the "injector side" connector. The only other way I can see in is to strip a small section of the cable to gain access to the wire within, and for future reliability reasons, I would rather not go that route.
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