1993 Sportster weak spark

Discussion in 'Electrical' started by GscottB, Aug 29, 2012.

  1. GscottB

    GscottB Member

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    Problem started - bike would not idle and pretty much run only at higher RPM (or with choke on). I found very weak spark and changed plugs and coil - same problem. I then found a melted cam sensor - replaced that. I still have same condition. I have the factory manual and preformed all the tests (best of my ability). But I must be missing something. I have purchased a new module but in fear of destroying it trying to work through this. Could a bad module have destroyed my sensor? And now that I have replaced the sensor, may I have damaged the new one in trying to test? Any input would be well appriciated.
     
  2. tourbox

    tourbox Senior Member

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    Has the bike been sitting a long time? If so then maybe your carb. needs cleaning due to running with choke on. Also ck. your vacuum for the VOES switch to make sure it is working. Sometimes the hose will get a crack in it. Don't recall if '93 had a vac. pet cock or not. If it does then vac. hose goes from carb.,then T's to the pet cock and VOES switch. You can ck. the switch by placing a vacuum on the tube and ck. the 2 wires off the VOES with a VOM in ohms mode.The switch is open until Vacuum applied then goes short. One lead goes to ground,the other to your ECM.When shorted it Advances the timing.There is also a test for the Cam sensor plate and wiring to it if you have a manual.
    tourbox
     
  3. GscottB

    GscottB Member

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    Thanks for reply tourbox, The carb was cleaned and tank lined in the spring. I had been riding the bike regularly until this happened a few weeks ago. I have not looked into carb issues because I already know I have terribly weak spark. And for VOES, I have preformed all tests in trouble shooting ignition. One thing I may mention is that my battery needs replaced. It will lose charge after a couple of days setting. But I proform tests with a trickle charger on at 13+ Volts. Could this be my problem? I don't wan't to throw $130 at it and possibly still be broke down.
     
  4. Dr. Dolittle

    Dr. Dolittle Experienced Member Staff Member Moderator Contributor

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    You need to load test the battery all on its own - disconnected from the trickle charger.
     
  5. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

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    The running only with the choke on or at high revs would tend to indicate that you have enough spark to ignite the fuel air mixture however it seems to me that the fuel/air mixture is wrong and i would tend to think that this sort of problem is often caused by an intake leak between the inlet manifold and the head or the inlet manifold and carb as any air drawn through a leak will have no fuel with it and weaken the mixture pulling the choke knob out adds more fuel and the engine gets sufficient fuel for the amount of air
    With the engine running spray carb cleaner / wd40 with the small tube that comes with the can around the joints of the inlet manifold and listen for any change in engine speed if there is any change you have found the leak just replace the gaskets and you should be good to go

    Brian
     
  6. tourbox

    tourbox Senior Member

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    If you performed all the test for the sensor plate & module per the manual,did they pass or fail each test. On your original sensor plate was the sealing compound running out of it? If it was that is usually an indication is it's on the way out. Not sure if the module could ruin the sensor,possible though.Maybe Hoople could answer that.Providing your charging system is good, I would go ahead and replace the battery anyway seeing as how it won't hold a charge. Load test it first as Dr. Dolittle suggest. Your weak battery could be pulling the charging voltage down enough while running that your getting insufficient voltage for the ign. system. I could be wrong on that though. I wouldn't put the new module in until getting your battery problem solved. Electrical Parts are usually NON-Returnable.
    tourbox
     
  7. BUBBIE

    BUBBIE Well-Known Member

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    I agree with above in bold, as I had that problem once on my older '95 sportster and I did need the battery re-newed. Then replaced the v.regulator as stator was bad.

    I would do the "Whiff test". Take off derby cover and If it smells BURNT.. Stator problems...

    signed....BUBBIE
     
  8. Jack Klarich

    Jack Klarich Expert Member

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    http://www.hdtalking.com/archive/t-47714.html Have a look here before you throw any more parts at it. Now you could keep throwing parts at it and still not know what the problem really was, IMO a bit more info could save you $$$
     
  9. GscottB

    GscottB Member

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    I appreciate all the replies! Charging system was checked right after plugs and coil (hard to describe everything done in a moment). I will get a new battery next and try that. I just can't figure that if I've got 13+ volts - why I don't have nice spark! Maybe that is it all the while - read low battery over works. I will tear into the carb again - did a superb job on it this spring, coated the tank as well. Leak test with WD-40 at intake first. What ever I do, do not want to destroy new module (or senor for that matter).
     
  10. BUBBIE

    BUBBIE Well-Known Member

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    Could it be BAD sparkplug wires??? (plus the carb)

    How old are they? Not expensive to replace them IF old.

    HD SE Colored ones to High Light the bike.:D

    signed....BUBBIE