Mattman928

I am tracing the ignition circuits on Sheet 10 of the wiring digrams. It seems that the control is a negative voltage setup, is this correct??

For example, if the LH fires the LH Relay, then +12v is supplied to the Ignition Control, Flappy, and Tank Vent. The Ignition Contol module, if the thermo couples are reading fine, will supply a constant +12v to the injectors.

So If the LH Relay is fired, then the Flappy, Vent and injectors (via Conector "4 (section K90)" and Connector "1 (Section M89)") are supplied with a +12v steady signal. If that's the case then the LH would have to supply +12v from pin 18 to set the injectors to Off (presumable their Normally Closed Condition).

If this is the case, then if one is trying to start the car, should we be abl eto read a steady +12v with the multimeter on any of the RED/YELLOW wires at the injectors.

Is this true?????

John Speake

12v is fed to one end of the injectors, pin 18 LH pulls the other side of the injectors down to ground to fire them. You won't see these signals with a meter as the injectors are only switched on for 3mS every engine revolution at idle speed.

fraggle

Matt's got a cool o-scope so he should be able to configure it to detect a signal - but he hasn't gotten far enough to get the motor idling. I'm going to guess he's measure 12V on the injector and it will never go to ground, given he isn't flooding the motor and the current "steady state" is Zero RPM.

Ed Scherer

In case it's useful, you can check out a post from about half a year ago where I show some oscilloscope traces for the LH that include pin 18 (fuel injectors ti).

Mattman928

I checkout the thread, but the pictures didn't come up. I do see the text on the setting for the O-Scope that should be handy.