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Car Forum / Chevrolet / Chevrolet Trucks / January 2006New thread...EST/ESC and knock sensor questions...
Ok...I think I've identified the burned up pigtail coming off the back of my HEI. Again, this is an '86 K5 Blazer, with the weird-a.s 5-pin ignition module. On the back of the HEI enters a small pigtail/wiring harness. It plugs into 3 of the pins on the ignition module. Does this go back to the Electronic Spark Timing / Control? I know it shouldn't have a real "ECM" because it was carbureted, but I believe it does have the EST. I don't know to what degree electronics played a part in the original Quadrajet. That carb is off the truck and it's running an Edelbrock Performer 600cfm. There ARE a couple of unused wires/connectors that end up in the vicinity of the carb that I assume would've been attached at some point. If the harness I'm referring to does indeed go to an EST unit, is it necessary to get the truck to run? Can it be bypassed in any way? The pickup wires connect in between this connector and the actual ignition module. A picture of all the parts can be seen here... http://www.absolutepickens.com/K5/Damage/Distrib_guts.jpg Thanks, ~jp > Ok...I think I've identified the burned up pigtail coming off the back > of my HEI. [quoted text clipped - 20 lines] > Thanks, > ~jp Yes it is the ESC pigtail. Yes your truck does have a ECM. You can convert to the older NON-ESC module and pig tail by using a NON-ESC magnetic pick-up. With out the CCC, ESC isn't doing you one bit of good (not that it ever did with a vaccume advance distributor) Charles Just sent you an email to your Yahoo account... ~jp > Just sent you an email to your Yahoo account... > > ~jp Got it. Ill send it out tomorrow (since I have to ship stuff then anywho). Charles Thanks again... ~jp If you want to simplify things, scrap the ESC distributor! Get a regular HEI and drop it in. Less to go wrong. > Ok...I think I've identified the burned up pigtail coming off the back > of my HEI. [quoted text clipped - 20 lines] > Thanks, > ~jp Well, simple is always better...but a replacement pigtail is on the way. I did manage to piece one together using a replacement connector and new pins with the other original (unmelted) connector. I don't feel good about using it though. I know the actual electrical connections will be fine, but it's designed to fill the square hole in the back of the HEI and I'd have to figure out a way to duplicate that part first. Charles found the pigtail in his stash. I may try mine just to verify connectivity and all but, again, I'd feel better about using a factory part. It's 9:30am now, and I'm just making the first cup of coffee. Hopefully I'll get a good deal done today. Sucks though, cause I have to walk to a parts store if I need anything... ~jp Ok, I've been screwing with the truck, trying my damndest to get the heater / a/c harness out from the dash. I've damn near disassembled the whole dash. Not fun, considering I'm sick. Anyhow, was doing some thinking on the ignition module situation. It's the 5-pin module made to connect to the ESC to detect spark knock and then retard timing as needed. The 3-pin side connects to the pickup coil via a pass-thru connector (which only uses 2 of the 3 pins). The 3 pins "pass through" this connector, which allows the ESC harness to be connected. I have a new 4-pin module already. Would using the 4 pin module and just not connecting the ESC allow the truck to run until I get the new 5-pin module and harness? ~jp Never used an ECS HEI. Any vehicle I ever had that had one, I installed a standard HEI. so I'm not 100 sure if not having every wire hooked up would be fine or not. Sorry. > Ok, I've been screwing with the truck, trying my damndest to get the > heater / a/c harness out from the dash. I've damn near disassembled [quoted text clipped - 12 lines] > > ~jp Well I found bypass instructions for the ESC. Apparently the ESC was such a POS that Chevy released a service bulletin on doing that exact thing. But that procedure still involved the 5-pin module. I'm suggesting switching to the 4-pin module. However as likely as it is, there's no way of knowing if my module is toast till I try to start it. I have my home-made ESC harness until the replacement from Charles arrives. It's not perfect, but it would let the truck run at least. So we'll see. ~jp > Ok, I've been screwing with the truck, trying my damndest to get the > heater / a/c harness out from the dash. I've damn near disassembled [quoted text clipped - 12 lines] > > ~jp If you use a 4-pin moudle's matching magnetic pick-up. Differance between ESC and NON-ESC HEI one wireing stub harness, one magnetic pick up and one module. Charles What's different about the pickup besides the fact that there's a different connector? ~jp A standard HEI is completely self contained. The only hookup needed is a 12V power source and a timed vacuum source. The ESC HEI has a computer controlled timing retard that I have never heard good things about. > What's different about the pickup besides the fact that there's a > different connector? > > ~jp Well that's exactly my point... eliminate the rear harness altogether. That's what goes to the ESC. There's also a special connector on the 12V Pink wire that runs to the cap that you're refering to, that splits the pink wire off to ALSO go to the ESC. So...how about removing that 12V feed to the ESC, and disconnecting the harness to the HEI. At that point you'd still have a 5-pin module, and it probably wouldn't run. HOWEVER, replace the 5-pin module with the 4-pin. As I stated earlier, the pickup coil connects BETWEEN the module and the ESC. It uses a 3-pin connector, but only 2 of the wires go to the pick up. The 3rd is straight from the ESC to the module. Again, regarding the pickup coil ONLY, what is the difference besides the connector that goes to the module. It's a coil of wire with 2 leads coming off it. I think converting it to a 4-pin module is easier than we think. I did a little Googling, and found many performance kits that do this very thing. Many say specifically that "the knock sensor is not retained", thus eliminating the ESC from the picture. To summarize...from what I can tell, the difference between an ESC HEI and standard HEI is the addition of the ESC and an extra pin on the module. Remove the ESC altogether, replace the module with a 4-pin model, and it should work fine.... ....In theory.... ~jp Not having the dist in front of me, I cant give accurate advise. Trying something new is always exciting. If it looks like it would work, go for it. What's the worst that could happen? It wont run...wait, its not running now, so, nothing to lose! > To summarize...from what I can tell, the difference between an ESC HEI > and standard HEI is the addition of the ESC and an extra pin on the [quoted text clipped - 4 lines] > > ~jp Well I made a replacement harness to go back to the ESC from the remnants of the old one and a new connector. It should work fine, but I don't like the fact that it doesn't seal between the distributor base and cap. I've been Googling the newsgroups all this morning, and from what I can tell, replacing the ESC HEI setup for a non-ESC setup will require the timing to be pulled back (retarded) some. Some folks are even talking about setting timing with the ESC harness disconnected, as if it'll still run without it. This is all just making me ponder even more. And everybody seems to find a way around the ESC. Apparently it's a real performance killer, and has no emissions value to it. I'll post the results whichever way I decide to go. I had a relapse with my cold, and may reluctantly go to see the Doc today...Ugh... I hate being sick when I could be wrenching. ~jp Well good luck with it and I pray you get better soon! > I'll post the results whichever way I decide to go. I had a relapse > with my cold, and may reluctantly go to see the Doc today...Ugh... I > hate being sick when I could be wrenching. > > ~jp |
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