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Electronic Spark Control question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Dunc03, Jan 22, 2003.

  1. Dunc03

    Dunc03 1/2 ton status

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    My ESC is screwing up and making the timing eratic at idle. When I put a timing light to the thing it jumps around anywhere from 2- 20 degree off of where it should be. Has anybody ever had this problem before. Is it the knock sensor going out or the ESC module behind the glove box. It doesn't do this evertime it starts up, just when it feels like it. Is there anyways to just by pass the system all together. IF anybody has any idea let me know. There was another guy asking the same question ealier, but his was related to a 87 that is computer contolled. Thanks for the help
     
  2. 4x4Freak

    4x4Freak 1/2 ton status

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    You can replace it with an older dist. if you want to eliminate it. Or you can modify yours, but you will need to change the module and maybe the pickup coil(not sure on this, but I know the connections are different, might be able to change the ends). Everything else will be the same. You might pull the rotor and check the mech. advance weights. It might be possible that one of the springs broke and isnt holding it in place all the time.
     
  3. pismorat

    pismorat 1/2 ton status

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    My dad's suburban had the same problem, oil ended up getting up the distributor shaft and shorted it. He replaced it and is fine now. /forums/images/graemlins/truck.gif
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    OR, could your engine actually be knocking?

    I know people have problems with the EST, but is it really a design flaw, or the fact that its been working constantly for 20+ years? Retarding timing based on knock ISN'T a bad thing, all new vehicles do it.
     
  5. Hossbaby50

    Hossbaby50 3/4 ton status

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    Just ditch the ESC. A local speed shop did it to mine when I had the dis. rebuilt. It ran a hell of alot better.
     
  6. Dunc03

    Dunc03 1/2 ton status

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    Any idea how they just got rid of the ESC system. When its running and I unplug the connection from the distributor, the engine dies. Its like the ESC has to be in place to ground the system or something. The power from the coil comes from the fuse block so I know the power does not come from this system. Could you take a look at your and see if they just spliced some wire together to bypass it. Thanks for the info
     
  7. Dunc03

    Dunc03 1/2 ton status

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    The issue is that I had to rewire the vehicle because of a fire. Upon rewiring I had no instructions on how to wire in this system. The system has power or else the engine would not crank at all. I need to bypass the system to get it running right now. I'm waiting on a wiring diagram that I ordered to determine the exact wiring on the system. I'm sure that there is not a knock, because the engine was timed perfectly before this started happening. I timed it myself, but I also had a professional mechanic check it. Aside from that the system is only supposed to retard the timing when labor knock are detected. These are often cause when pulling a load at cruising speeds, thus the system should not be working at idle.
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    How does the system know you are moving or not? (never had heard that before)

    *Believe* you can do it with a module swap, but have you searched on this board already for past posts on this? I vaguely remember posts on it.
     
  9. Dunc03

    Dunc03 1/2 ton status

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    There is only one other post I found about it and it is the same question, but no concrete answers. I'll try the swao and see what happens but I think the module is what is actually the cause. Thanks for the ideas
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    Yep, couldn't find any post on it either. Here's a silly question, does your distributor have a vacuum cannister on it? Seems that if thats present, you should have everything needed to convert to non ESC, but I don't know that for certain.

    And I believe there is a vacuum switch in the ESC system (on the firewall) which is probably what determines if the engine is under load or not. I was thinking vehicle speed sensor, but there were two vacuum switches on the firewall, one for the 700R4 lockup, one for ESC (I think).
     
  11. R72K5

    R72K5 Banned

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    some ESC distributors have vacuumn advance and soem do not i have found out, had an 86 wagon with esc vacuum advance and worked in an 86 c10 with vacuum advance esc in it also, and had an 84 z28 with esc and no vacuum advance, its hit and miss really, seems like late 80s just before tbi were the oddball ones with vacuum and esc together, odd...

    you would need a non esc carb and hei to rid of the system, unplug the O2 and knock sensors and MAP sensor als if equipped, not all models had MAP, the 86 c-10s dont, the 86 wagons did and 84's too


    also theres a way to cross a coupel wires on the esc ecm undert he dash and be good to go to disable ecm control, i forgot wehich ones to cross though, hmmm..,.., would work on vacuum advance est dizzies


    wierd,,
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    Ok, '81 up carbed cars (federally, GM) are all CCC, so they'd have everything associated with that...map, baro, O2, TPS, etc.

    Trucks were hit or miss up 'till 1987 apparently, and they could have had CCC, a "dual capacity" solenoid, or a plain old Q-jet. CCC was the only one that *necessitated* the different distributor AFAIK, but I can't comment on the dual capacity system, because I only know what the carb looks like.

    So he doesn't necessarily have to change the carb (and maybe not the dist., really don't know) just because he has ESC.
     
  13. Hossbaby50

    Hossbaby50 3/4 ton status

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    Ok, I may be off base here but here goes:

    You will most likely need to swap out your carb to run without the ESC. Your carb for an 86 should be partially controlled by a computer of some sort. This is what I was told by DesertDueler about his 86. I have an 85 and my truck only had the ESC for the distributor not the carb too. On HEI you should only need to hookup one wire to the distributor to make it run. It only needs to be grounded (to the motor) and have the one keyed positive source to the distributor to get it to run since the coil is incap. I would guess the way to bypass the ESC on the Dis. would be to hookup a keyed positive source wire to the dis. and remove the one from the ESC module. The carb I can't help you with. i have heard swapping to a carb from and 81-85 is the easiest way to get rid of that.
     
  14. 85Blazer

    85Blazer Registered Member

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  15. aandpman

    aandpman 1/2 ton status Premium Member

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    /forums/images/graemlins/thumb.gifI did the very thing listed in the article on my 85. Mine had stared dying suddenly and *maybe* restarting. Bought a Summit HEI dist and just dropped it in. Of course my carb didn't have any controls on it so there was no prob making the change.
    Been running great for 3 years now. /forums/images/graemlins/truck.gif
     

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