How To: Set CO Dwell

[Domi]

This PDF is one of the better how-to's I've come across for setting CO
Attachment 57912

Thank you for sharing this PDF

[Ron]

This PDF is one of the better how-to's I've come across for setting CO
Attachment 57912

It's very well done but some of the settings and procedures are different for a D...

[Ron]

The manual says to "switch dwell operation for 6 Cylinder engine....dwell operation for duty cycle is 50%" +/- 3.0%"
(WSM D:04:01, CO EMISSION ADJUSTMENT, 2, 11) [Open Loop]

The Specification section says "Normal Operation (Sensor connected and CO properly adjusted) 35-45° (reading pulsates)" (WSM D:04:01, A) [Closed Loop]
Here, they give Dwell values with the meter switched to 4 Cylinder (w/o mentioning it, anywhere)!
AND people have been using these checking values as a setting value by averaging 35-45 = 40° and selecting 4 Cyl on the meter instead (or 20° on 8 Cyl). This is supposed to be for checking the closed loop operation, not setting CO while in closed loop! [Note IF the system is OK, it would not matter.]

Closed Loop Setting Values:
O2 Sensor Connected
Duty Cycle of 44.444% OR Dwell of 40°, switch in 4 Cyl mode = (26.666° in 6 Cyl mode, 20° in 8 Cyl); Pulsing.

The section continues with "Oxygen sensor disconnected - 40-50° (steady reading)" (WSM D:04:01, B)
This is correct, if your meter is switched to 4 Cyl instead. [Closed Loop!]
This is the same as the CO EMISSION ADJUSTMENT section (above).

Open Loop Checking Values:
O2 Sensor Disconnected
Duty Cycle of 50% OR Dwell of 45°, switch in 4 Cyl mode = (20° in 8 Cyl mode, 22.5° in 6 Cyl mode); Pulsing.

We have: the manual using a 6 Cyl setting and then 4 Cyl later (w/o mentioning it anywhere), setting the CO in closed loop and checking in open loop (that's backwards), and meters that don't have 4 Cyl so it is converted to 8 Cyl. Made for a lot of confusion and questions for years...

Why they don't use 6 Cyl all the time is a mystery to me.

All setting/checking values can be found below:

SETTING CO Using Dwell-Duty Cycle-2.jpg

P.S. Thanks to Dave (Bitsyncmaster) for bumping heads with me!

[82DMC12]

I'm going through these settings now. How does one "apply 1.5V to sensor lead"? Is there some device or multimeter that does this?

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[Bitsyncmaster]

I'm going through these settings now. How does one "apply 1.5V to sensor lead"? Is there some device or multimeter that does this?

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You use a flashlight battery. Just tape some leads on it.

[82DMC12]

You use a flashlight battery. Just tape some leads on it.

Smart! Thanks!

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[82DMC12]

You use a flashlight battery. Just tape some leads on it.

Dave, should have asked - do you touch both leads to the terminal on the end of the sensor wire, or do you ground the negative and apply the positive to the wire?

[Bitsyncmaster]

Dave, should have asked - do you touch both leads to the terminal on the end of the sensor wire, or do you ground the negative and apply the positive to the wire?

You ground the flat side and touch the wire to the + (side with bump).

[AugustneverEnds]

I recently had my distributor and warm up regulator rebuilt and need to check the dwell, I have a digital dwell meter (I know analogue is better). My question is, do I use the 8 cylinder setting like its been shown with the analogue meter, the 4 cylinder and double the figures, or the 6 cylinder setting?

[82DMC12]

I recently had my distributor and warm up regulator rebuilt and need to check the dwell, I have a digital dwell meter (I know analogue is better). My question is, do I use the 8 cylinder setting like its been shown with the analogue meter, the 4 cylinder and double the figures, or the 6 cylinder setting?

Without knowing the specifics of your digital meter, I like to use the 8 cyl setting on my analog because it seems like the settings/numbers for 8 cyl are more the vernacular around here.