NOS Duraspark III Ignition Module / Yellow Grommet / E1AZ-12A199-A

Rare Duraspark III Yellow Grommet ignition module. Reasonable price. Some of these go for $150 Used.

E1AZ-12A199-A / Motorcraft #DY-297 Fits:

81: E-F-U100/350 - 351M/8 with High Altitude Carb
82/83: F-U100/250 - 302/8 with High Altitude Carb
82/83: F100 with M/T - 230/6
82: E150/250 - 351/8 with Hi Altitude Carb
83: E100/250 - 300/6 with Calif Emission A/T-all / and M/T with 8501 GVWR
83/87: Ranger - 140/4 with High Altitude Carb



https://www.ebay.com/itm/182475837051?epid=598713043&hash=item2a7c684e7b:g:~HQAAOSwB-1Yufg2

My understanding is that the yellow grommet modules add a bit more dwell and have the ability to interface to a vacuum sensor via the third connector and that can modify timing as well.  Not sure I understand why you'd need vacuum to the dizzy and vacuum to the ignition module, but...

Actually the Duraspark III uses a Crank Position sensor, and the EEC-III for timing. It also uses a feedback carburetor to adjust fuel mixture. Possibly why it was also used for high altitude models, instead of just California Models.

Now the MCU-DSII system my 1981 has, is a hybrid. It uses the MCU to control timing by using a EGR Solenoid tee'd into the DS-II vacuum advance line to the Carb. The base timing is set to 6 degrees, with the vacuum unplugged from the distributor.  The carb is designed to have ported vacuum at idle to the distributor advance, this brings the timing up to 14 degrees at idle. The MCU controls timing by bleeding the vacuum off the distributor, using the EGR Solenoid, to keep timing around 10 degrees idle.  The vacuum advance then works normally like normal systems also using centrifugal advance.  A pretty complicated system that even confuses some of the smog guys here.  This is the system I think you are thinking of.

That's probably the one I was thinking of.

And speaking of thinking, those engineers must have spent a lot of time back then thinking up ways they could cheaply make the limited systems they had available to complicated things.  I realize that none of it happened overnight and it was layer upon layer of complication, but it got complex!

I think I remember someone over at FTE (it may have been Ralph) who said that with the "high altitude" package, the truck had to be turned off and re-started in order to re-set the calibration at different altitudes.

Or something like that.

I know my 1981 does exactly that, so it probably was me that said it.

The MCU has no run "Memory" so it sets the fuel adjustment every time the engine is started. It never learns the optimum ratio like the EEC-IV or V does. (Not sure of the EEC-III, but I don't think it does either)