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Old 01-27-2013, 04:52 PM   #59
Boon Booni
Red Clay Halo
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Joined: Aug 2003
Location: Richmond, Va
Oddometer: 13,794
Originally Posted by Queen of Spades View Post
Should voltage only goto the coil when the engine is being turned over? If I understand these systems, I think that's right.. then I'd need to hook up everything, and slide my POS lead into the coil blue/white connector, and to the battery ground for the other. Please correct if I have this wrong.
Usually there will be a constant 12 volts to the coil. The coil is fired by cutting voltage, usually by controlling the ground side of the coil.

EDIT: Looking at some of the online wiring diagrams, something doesn't look right. Shows blue/white wire from the tach to the coil to the ECU. Either they are supplying power to the coil from the tach (?) or the diagrams aren't correct... or the coil is running on voltage from the ECU and the coil is frame ground?? If it's the last then you may not have a constant 12volt at the coil. It may be pulsed. I'm not familiar enough with my 640 yet to tell you the correct answer.

EDIT EDIT.. Your post answered my question. The check from BL/W to ground means the ECU is supplying power to the coil, but I still don't know if it's pulsed or constant.

Your other check, BL/W to Ignition wire has to be incorrect. That check should be Ignition Wire to Ground = 10,80 – 16,20 kΩ. (you'll need to change the meter back to 20k ohm for this check)

Boon Booni screwed with this post 01-27-2013 at 05:35 PM
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