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What is this box?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Predator, Nov 12, 2001.

  1. Predator

    Predator 1/2 ton status

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    While changing my heater core on my 83, I noticed there was a computer right above the heater box, above/behind the glove box. It has a harness going out the firewall with a weatherpak connector and a couple of other wires with it. Nothing is hooked up to anything. Should it be going to something or can I yank it??

    My K5 Buildup: <a target="_blank" href=http://www.geocities.com/gettin_deep>http://www.geocities.com/gettin_deep</a>
     
  2. Hossbaby50

    Hossbaby50 3/4 ton status

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    It probably was a spark control box. I had that on my 85 and I had it disconnected and my distributor was set up to act like normal. Thats the only computer that I know of on a truck that old.

    My Chevy isn't broken, its just out of gas.
     
  3. jimmyjack

    jimmyjack 1/2 ton status

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    Your right on the money. It's an anti backfire/pinging thingy thing

    That jeep thing? Yah I understand it....... Like my Blazer? <a target="_blank" href=http://community.webshots.com/user/blazerk5>http://community.webshots.com/user/blazerk5</a>
    Jim
     
  4. HarryH3

    HarryH3 1 ton status Author

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    GM Called it "ESC" for Electronic Spark Control.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     
  5. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    The ESC is disconnected on my truck as well. How important is it? My truck seems to run great, BTW........



    <font color=blue> NEVER FORGET, NEVER FORGIVE, NEVER SURRENDER<font color=blue>
     
  6. Hossbaby50

    Hossbaby50 3/4 ton status

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    Its not important at all. I think its one of those things that is supposed to help drivability. I have had mine disconnected for 4 years now with no problems.

    My Chevy isn't broken, its just out of gas.
     
  7. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Can anybody explain to me exactly how it works? And how it was originally hooked up to the engine?

    Like I said, my truck runs great[​IMG], but I'm just curious......



    <font color=blue> NEVER FORGET, NEVER FORGIVE, NEVER SURRENDER<font color=blue>
     
  8. Pure Insanity

    Pure Insanity 1/2 ton status

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    Yeah its the ESC. You have to convert the carb and dist. to non computerized carb and dist to be w/out it. I had an ESC dist whip me for 2 weeks before I figured it out when I first put my Blazer together. I had a Holley carb and the ESC dist hooked up. It would run if I hooked up an ign. bypass box that my dad had at the shop. Disconnect it and it would just spin over w/ no spark. Changed out to a reg. HEI and it fired right up. One part wont work w/ out having the other to read. I did the same conversion on my camaro.

    If ya can't stop.......Smile as you go under! [​IMG]
    PIC of mine from flblazers site<a target="_blank" href=http://www.flblazer.alloffroad.com/photo3.html>
    GO</a>
     
  9. Hossbaby50

    Hossbaby50 3/4 ton status

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    I had mine converted when my distributor was rebuilt to run with out the ESC. I am not sure what they did though. I believe that the ESC was to back off the timing if the motor was starting to ping or knock. It was supposed to compensate for bad gas, altitude, etc that could cause the motor to knock.

    My Chevy isn't broken, its just out of gas.
     
  10. Blue85

    Blue85 Troll Premium Member

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    That's right, but how does it control timing? I don't think that it has a knock sensor. I think that it montiors engine vacuum, but what else does it have to go on? And how does it control the timing? Does it do it electronically, by interfacing with the spark module?

    Vacuum advance, mechanical advance and electronic retard, huh?

    <font color=green>There's nothing like the smell of a rich V-8 in the morning...</font color=green>
     
  11. Hossbaby50

    Hossbaby50 3/4 ton status

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    I'm really not sure how it controls the timing. I just know that I read or heard that the box controls knocking and pinging, and I would assume that it does that threw controling the timing.

    My Chevy isn't broken, its just out of gas.
     
  12. Pure Insanity

    Pure Insanity 1/2 ton status

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    Ok heres a theory, the carb has sensors on it to moniter the position of the accel. pump, which is directly equal to the throttle postition. (At least this is the way it was on my 6 cyl Camaro.) The sensor tells the ESC box whats going on and how to deal w/ it. As far as load is concerned. It also has a vac. advance. There is a ring hooked up at the very bottom of the dist, which advances or retards the trigger ring to tell the dist when to fire. (I am going solely from memory here. I havent been inside one of these dist in a while.) Maybe this will help. Its actually one of those things I can see in my head but cant remember clearly enuff to tell it.

    To simplify it, Its basicly like the vac. advance, but it will both advance and retard timing and is worked by sensors instead of vac.

    I hope I am correct on this. If not I am sure someone will correct me.

    If ya can't stop.......Smile as you go under! [​IMG]
    PIC of mine from flblazers site<a target="_blank" href=http://www.flblazer.alloffroad.com/photo3.html>
    GO</a>
     
  13. Blue85

    Blue85 Troll Premium Member

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    Well, the sensor that measures the accelerator pump position would actually be a Throttle Position Sensor. The only carbs that had those were the electronic carbs. Those didn't really go into trucks, but the electronic carbs cars had ECMs that controlled timing, injection and everything and no ESC box.

    But let's suppose that the ESC box does know throttle position. What would that tell it to do with timing? The mechanical advance advances timing based on engine speed (faster=more advance). The vacuum advance advances the timing based on the engine load (read via a vacuum signal). The only other thing that should need to be done to timing is to retard it when there is knock. As far as I know, the only way to do that is with a knock sensor.

    Anyone ever find a knock sensor on their engine?

    On the same note, some trucks had a transmission-based spark controller. Is that different or the same as ESC? I don't know of anything in a transmission that should have anything to do with ignition timing except for indicating what gear the vechicle is in. Then you could run additional advance while cruising on the highway. Some 700R-4's had a switch that turned on when the truck was in high gear. This was used to turn on a vacuum switch to allow the EGR system to work only in certain gears. Does this signal also go the ESC box?

    <font color=green>There's nothing like the smell of a rich V-8 in the morning...</font color=green>
     

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