81-F150-Explorer Posted January 18, 2023 Share Posted January 18, 2023 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 Link to comment Share on other sites More sharing options...
Gary Lewis Posted January 18, 2023 Share Posted January 18, 2023 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... Link to comment Share on other sites More sharing options...
81-F150-Explorer Posted January 18, 2023 Author Share Posted January 18, 2023 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. Link to comment Share on other sites More sharing options...
Gary Lewis Posted January 18, 2023 Share Posted January 18, 2023 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! Link to comment Share on other sites More sharing options...
LARIAT 85 Posted January 20, 2023 Share Posted January 20, 2023 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. Link to comment Share on other sites More sharing options...
81-F150-Explorer Posted January 20, 2023 Author Share Posted January 20, 2023 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) Link to comment Share on other sites More sharing options...
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