Smoking Ballast resistor...?

Interior and Electrical

  1. Toro67

    Toro67 Well-Known Member

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    Hi fellow Mopars

    I had the lean-burn removed from my 318 2bbl LeBaron last year and replaced with an electronic ignition system from Summit. After that the car ran fine all last season.

    This Spring I started it up with no problems. The trouble began when I put it in D and tried to drive. When I speed up as I normally would, it dies. Only a feather-light touch on the gas will make it crawl along and not die. When in Park it will rev just fine !

    So I crawled back home and googled some causes. Most answers pointed to the accelerator pump, so I checked the pump, and it seems to deliver fine. The fuel filter and fuel pump is new from last year.
    While checking the carb I noticed the Ballast resistor was cracked all the way though - split in half lenghtwise, but still connected. The resistor has also been replaced last year as part of the overhaul. It´s the type with 2 pins.
    Well I put on the old resistor and started up again. After a few minutes of warming up, the resistor starts to give off smoke and becoming really really hot. I turned off the car, measured the resistance to 1,5 Ohm, and here I am writing this. I suppose the previous resistor also cracked from overheating, but why ?
    When you do the lean-burn deletion, should you also change the ballast resistor to a different type ?
    Could the two problems (carb / resistor) be related ? As I said, it ran just fine all last year - no changes from then till now.
    Any quick help would be appreciated, since I have a friend coming over from the US in less than a week, who can take smaller spare parts over.

    Thanks in advance :)
     
  2. Aspen500

    Aspen500 Well-Known Member

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    What brand kit did you use? The new Mopar kits have quality issues (i.e. Made in China) and I've heard of problems with the ECU among other things. If it has an internal short to ground, or any other short to ground after the resistor, it will get very hot and fail. Doesn't have to be a direct ground short, it can be a partial path to ground. What I mean by direct is 0 ohms, partial could be 50 ohms, 500 ohms, etc. I you have a 4 terminal ECU, the single ballast is the one you need. A 5-pin (which hasn't been used since the mid '70's IIRC) needed a 4-pin. I remember seeing many cars with a 4 pin ECU that still had the dual ballast and wiring (from the factory I believe). At any rate, the 4-pin ECU was a direct replacement for the 5-pin but not vice-versa. The 5-pin had separate start and run circuits.

    It SOUNDS like you have weak spark from the description. It's enough for no load like idle or revving in park but under load. the spark gets "blown out".

    The short could be in the coil or somewhere in the wiring also, if there is a short that is.

    The resistor will get way too hot to touch normally. It's the way they work, converting resistance into heat. Another thing is, make sure you have the best quality resistor you can find. Cheap ones may not be made well and will crack, burn out, etc. I know, easier said than done to find a not Made in China junk.

    Maybe none of this is the actual problem, just trying to throw possibilities out there on things to check.
     
  3. Toro67

    Toro67 Well-Known Member

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    Hi Aspen500

    I used this kit from Summit: Summit Racing® Electronic Mopar Distributors SUM-851003
    It´s probably made in China... I have attached some pics of the setup.
    If your theory about the weak spark is right, the problems are related, and that´s a good thing :) The bad thing is that I am not an electric wizard. I do have a good multimeter though, so If I knew where and what to measure maybe I can find the short.
    The coil looks pretty cheap; maybe I should order a better one ?

    IMG_4364.JPG

    IMG_4365.JPG
     
  4. Toro67

    Toro67 Well-Known Member

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    I would like to upgrade the coil to an MSD Blaster 2, which comes with a matching ballast resistor. But after reading a lot of threads about HOT ballast resistors, one guy said that the ICU unit will not be able to handle the 45K Volts the MSD delivers. If this is true, there would be no point in upgrading the coil.
    Anyone running an orange/blue ICU with a 45K V coil ?
     
  5. Darth-Car

    Darth-Car Well-Known Member

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    Aspen500 you make an interesting point about the 4 pin verses the 5 pin systems, and I never have gotten a clear answer on the problem for years, but I lived it in reverse from your description with my 77 Volare', and it's 225 Super 6.

    I had the 5 pin control module start to go bad. So I went to my quality parts store in town, and purchased the high quality / performance brand Blue Streak module to replace the factory module. Blue Streak was the performance brand of what was Standard Automotive back then. I already had the high performance Blue Streak coil so I wanted the control module to match.

    I got it home, and took it out of the box. It had a tag on it that said this new design module only requires 4 pins to work in your car. It seemed strange to me, but I tried it anyway.

    The car ran lousy, and had little pep. I took the module back, and my friends behind the counter gladly replaced it for me.

    Remember how nice it was to see the same old guy behind the counter at the locally owned parts store? The guy knew you by name when you walked in, and he knew what you drove. While he would thumb through the huge rack of parts books you could chat about car repairs, and upgrades, because he had done them all. You don't get that service from the 12 year old kid behind the counter at the chain store today. You know the kid; the one who thinks he upgraded his toy car with an ice cream cone shaped air filter for $100.oo!

    Well the replacement module was no better. So I called the parts department at the dealership, and sure enough the MOPAR module was available in 5, or 4 pins. Their parts department was open until 11PM; so I headed out in the middle of the night for a part.

    I put the new 5 pin module in the car, and hit the key. The engine sprang to life like it was a belching fire beast! The car had never run so good. So yes I believe there is a difference in the 4, and 5 pin modules, but don't ask me the science behind it; and I am sure with your years of wrench turning experience you probably have just the right answer in this situation; it just sounds right. In my case my mileage decided to vary. :) Cars are quirky, and there is sometimes no good answer why something works on one, and not on another.
     
  6. Oldiron440

    Oldiron440 Well-Known Member

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    I've had that happen in the same brand of coil and mopar chrome box were one new part didn't work well and the next did.
     
  7. Aspen500

    Aspen500 Well-Known Member

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    The 81 D150 I had until 1998 had a 5-pin ECU. It also had an odd dual pickup distributor (not ESC or Lean Burn) with a relay to switch pick ups between start and run. Anyways, one night after work, it wouldn't stay running and only "ran" with the key in the crank position and I had a signal from both pickup coils. The replacement ECU (from my stash at home) had only 4 pins but the engine started and ran perfectly fine, same as it did with the original 5-pin. It was a Chrysler ECU though, not aftermarket.

    Toro67, sorry I didn't get back to you before. I guess if you don't find any obvious paths to ground int he circuit, the next thing I'd do is "substitute known good part" (hey, even the factory service manuals say that sometimes) and try a different coil. Run the car and keep an eye on the resistor. Also, check the back of the resistor to be sure the resistance coil is encased and not exposed, possibly touching the firewall or the hold down clamp.
     
  8. Darth-Car

    Darth-Car Well-Known Member

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    I have seen more than once one of the old ceramic Ballast Resisters get cracks along the back side around the rectangular area where the resister elements are sealed in. Those hair line cracks can let in just enough moisture to make all kinds of funky thing happen.
     
  9. Toro67

    Toro67 Well-Known Member

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    Hi guys
    Thanks for your inputs on this. I have ordered a new ballast resistor and a new MSD coil. just in case the old one is damaged.
    By closer inspection, it turns out that the smoking resistor had been lying in a puddle of oily goo at the bottom of the used spare parts box.
    I did not notice this when I installed it, and this has off course been the reason it was giving off smoke after a short warm-up. I will take the car for a test run this week-end when the spare resistor has arrived, and see what happens.
    As you say, the resistor is a cheap part, and it may just have died just because of that, and not due to any faults in the wiring...

    It´s great to have such a pool of knowledge to draw from when thing go iffy - thanks again :)
     
  10. BudW

    BudW Moderator Staff Member

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    Those ignition coils and ballast resistors run very hot when car is on. Don’t touch either or it will leave a burn (I have a few burns to prove that fact).

    A 5-pin will work in place of a 4-pin module – but sometimes not the other way around (a 4-pin in place of a 5-pin module). I’ve been told the 4-pin works for both – but experience has shown that not be true.

    If I was retrofitting a system (Lean Burn removal or (gasp) points), I would prefer the 4-pin system over the 5-pin for it does give more voltage on startups.

    A dual resistor (older style)
    Older Ballast Resistor.jpg

    Single resistor (two different styles, both interchangeable, except from point systems).
    Newer Ballast Resistor.png
    Ballast Resistor.jpg

    A quick tip: if a car starts when key is in “START” but dies just as soon as key leaves “START” – you have a bad “RUN” leg on your dual ballast resistor (5-pin system) or bad ballast resistor (4-pin system).

    If you have a 5-pin (dual ballast) system and car will not start when in “START” position but fires up just as soon let go of the key, then the problem is also a bad ballast resistor (the other leg of it).

    Most computer-controlled systems do not use a resistor.


    If you own an FMJ vehicle, I highly recommend you keep a few tools in the trunk along with a cheap volt/ohm meter, a ballast resistor (whichever kind your car uses) and possibly a voltage regulator and ICU. Maybe even other minor parts/tools, possibly. I do know the resistor and ICU are mostly reliable but can go at a snap of your finger as well.

    About 5 months ago, I drove to Taco Bell with my kids, and the "RUN" leg of my dual ballast resistor died. I was able to use the "START" leg to get home and replace the resistor with another one I had. This car has the 5-pin ICU with the dual resistor.
    BudW
     
  11. Aspen500

    Aspen500 Well-Known Member

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    Every car I've owned with the single OR dual ballast, there was always a spare, along with a cheap wrench to change it, in the glove box. I think those items were almost standard issue for Mopar glove boxes of the era. :eek: