'86 ECM - what's it do?
 

I have an '86 K10 with a carbureted 305 and 4-speed manual transmission. The Q-Jet is the non-computer variety (M4ME) and the HEI has a vacuum advance canister and a 5-pin module. I'm guessing that the 5th pin is somehow tied to the ECM that's located under the dash behind the glovebox; does anyone know exactly what it and the ECM do? I did a minor distributor overhaul over the weekend and after reducing end play the timing's a bit more advanced; would this cause any problems for the ECM? Thanks!

Brad

If you say that the 5th pin from the distributor goes to the ecm, I would say it retards the timing with the input from the knock sensor.

Hmph. That sucks. Anyone know if it's possible to somehow override this so that the ECM's out of the picture and the timing is only as how I set it? Perhaps a conversion to a 4-pin HEI is in my future...

Brad

You already answered your question. To eliminate the ESC you have to install an standard HEI distributor... :cool:

http://www.73-87.com/7387garage/drivetrain/escrepl.htm

That might help you out.

Make sure you read down to the bottom of the page. There are instructions there for converting an ESC distributor to a regular one. Instead of replacing it with a regular one, you can remove the ESC functionality by clipping and soldering a couple of wires.

Slonaker

Many thanks for the replies! Since I'm not sure how long I'm going to keep the truck I'll probably do the quick/short ESC disable for now, but if it looks like long-term ownership is in the future (the idea of swapping my '78 C10 cab and box to the '86 K10 frame has crossed my mind more than once) I might completely remove the ESC controller and convert to a 4-pin HEI. Thanks again!

Brad

disconnect the connector on the hei,ond cross terminal A and C on the lead comming out of the HEI.it will work fine

So you're saying to leave the connector disconnected and jump the A and C wires? I reread the 2 conversion routines mentioned above and notice that nothing's said about the connector being connected or disconnected, so now I'm wondering what the B and D wires do and if they're necessary with A and C jumped.

Brad

yes leave disconnected,cross A&C,leave original module in dist