Mattman928

I am pouring over the wiring diagrams and have a couple of questions:

1) Sheet 10 - The "Idle Speed Positioner" on section O90 of the drawing. Is this the Idle Stabilization valve? It is also connected to PIn 33 of the LH

2) Sheet 10 - The "Speed Sender" in section J83. Is this the infamous Crack Position Sensor? It's conencted to Pin 6 and pin 23 of the EZK?

3) Sheet 10 - The Thermo ELements in section K82. I assume that these are the exhaust manifold temp sensors for the injector safety shutdown circuit. These seem to be wired in series. If that is the case, how do they then determine whether to light the Red or Green LED on the Ignition control relay??

John Speake

1) Correct
2) Correct
3) Good question and I don't know the answer. I can only think that the sensors also have some resitance to chassis ground as well ? Then the whole thing would be a type of bridge circuit and able to trigger the correct LED as required.

jcorenman

The are wired in series, but with opposite polarity-- the two sensors are wired backwards to each other. Those are thermocouples, which generate a small voltage proportional to temperature. So the resulting voltage of the series connection is the difference in temperature between left and right ignition banks. A near-zero voltage indicates that the temperatures of the two ignition banks are about the same and both are working (or both dead); a positive voltage indicates one ignition-bank is cooler (and misfiring); and a negative voltage indicates that the other bank is cooler/misfiring. Cyl's 1-4-6-7 are one ignition bank (one coil and distributor), 2-3-5-8 are the other.

What year is your car? (Hint: add this to your signature).

John Speake

Ah ! that's how they do it, clever !

1-4-6-7 misfiring will show a red LED
2-3-5-8 misfiring will show the green LED

[QUOTE=jcorenman;8718849]The are wired in series, but with opposite polarity-- the two sensors are wired backwards to each other. Those are thermocouples, which generate a small voltage proportional to temperature. So the resulting voltage of the series connection is the difference in temperature between left and right ignition banks. A near-zero voltage indicates that the temperatures of the two ignition banks are about the same and both are working (or both dead); a positive voltage indicates one ignition-bank is cooler (and misfiring); and a negative voltage indicates that the other bank is cooler/misfiring. Cyl's 1-4-6-7 are one ignition bank (one coil and distributor), 2-3-5-8 are the other.

QUOTE]

Mattman928

I wonder how we test them at rest?? If one of these sensors goes bad it's generally an all or nothign deal (meaning an open or shorted circuit) so it should be easy to test at rest. Do they energize when the ignition is on but the engine is not running? Or only if the engine is running

Mattman928

I, for the life of me, can't figure out how to adjust my signature to add the vehicle (so I edited the Avatar)