My '54 chevy with 235 started running rough at speed recently. It has quickly deteriorated to the point that it will hardly idle. I haven't had a lot of time to look into it but started poking around today and checking the ignition wiring and everything seemed ok but when I touched the coil I darn near burned my hand. It was SUPER hot and I hadn't tried to run it in about 5 hours. I normally unhook the battery (for no particular reason other than I've always done that) but lately it's been hooked up all the time. Did the coil just go bad and cause this or did something else cause it? Where should I be looking? BTW, a previous owner converted to 12 volt. I put a new coil in last year (internally resisted). Thanks, Scott
1) I'd see if the coil was powered key off for some reason. Use a common test light to check. 2) Dwell is out of whack. Six cylinder dwell should be mid 30s? 3) Coil is internally ballasted? Does it say that on the coil? 4) Finally, some coils run hot. But shouldn't fry human flesh.
I suppose primary resistance of coil could be too low. That would make things hot. You check that with a ohmeter coil disc. Since you've changed coils, what's the correct primary resistance for a internally ballasted add on coil? I don't know.
Stupid. I had left the key in the run position. Probably why it was hot. Still doesnt explain the rough running though. Posted using the Full Custom H.A.M.B. App!
You need some kind of physical resister to the coil and points. When it says internal resister it means a resister built in to the wire in the harness of the car it is in. If you do not have a resister to the coil it will fry both the coil and the points and it will eventually not run at all. Steve
Did you use an aftermarket high performance coil?.... I used an Accel SuperStock coil, the round one, it was the proper coil for my system, and did the same thing you are experiencing....chased the problem for awhile before I determined the coil was junk.... The coil only lasted about 600 miles..
It's a bi-metal spring on the points. If the points are closed when you leave the key on, it gets hot. When it gets too hot it loses its springiness. Check it out. I bet the points don't have good spring-back now. That's probably the reason it's running rough. Replace the points.
I thought the internally resisted coil didnt need the wire resistor. Thats what i remember reading when i looked into what kind of coil to buy. Anyone know if i am right? Posted using the Full Custom H.A.M.B. App!
Just a standard parts store coil. Internally resisted 12V. Posted using the Full Custom H.A.M.B. App!
http://www.jalopyjournal.com/forum/showthread.php?t=745938&highlight=ignition+coil Read this thread and you'll find your answers
Scott, The whole system needs a resister wire or resister block before the coil and points to drop the 12 volts to about 7 volts or the points will fry. Check your points to see if the tip is discoloring. That will mean they are getting hot. I went through all this in the 70s with a 36 ford. Cooked the points until I realized internal meant the original wired systems wire. You must have a resister before the coil to be safe with voltage. Steve
More wrong info here than you can shake a stick at! There are 2 TWO kinds of coils for 12V systems ,one type require some form a external resistance either a wire normaly in the loom or the external ceramic block . The other style has the resistance built in like the Bosch BLUE coils for one ,most iginion parts companys will have one in their line. OP :Good chance you have now burned up your points by leaving the switch on which will cause rough running. Modern points sets with plastic rubbing blocks will melt throwing off timing until the engine won't run at all.
check the points, they could indeed be cooked. coil should still be ok, make sure it's not leaking oil.
Points dont look burned rough or discolored. The rough running started way before me leaving the switch in the run posn. I left it in the run position for a few hours. Posted using the Full Custom H.A.M.B. App!
Coil is oily on the bottom. There isnt an engine oil leak so its safe to assume the coil i think? Posted using the Full Custom H.A.M.B. App!
Ok Scott ,next step check the carb for dirt in the bowl/jets. If that checks run a compression check .Then valve clearance. Also timing.Oil on bottom of coil is probably from it getting to hot ,most likey still KO.
Check inside the coil tower , there is a screw that has a rubber washer on it , see if the screw is loose , looked for an oil leak for weeks before I found the loose screw in mine , got lucky , tightened the screw , leak stopped that was 3 years ago , so it doesn't seem to have adversly affected the coil . dave
Well that's good...then maybe the points are ok. But I'd pull gently on them and then let go to be sure they have good spring-back. Then just replace the coil. If that doesn't do the trick, pull a plug wire and hold it 1/2" from the plug while the engine is running, and see if the arc is blueish, stong and snappy. If it is, then your ignition system is working well. But if the arc is orangeish/pinkish and weak, you may have a bad condenser. It'll still spark, but not well. You might have a rich fuel condition though, and fouled the plugs. Pull a plug and see if it's black and sooty. But I think it's ignition. Usually, if the plugs are fouled, the engine will idle ok, but won't run well at higher rpms. Good luck.
Points spring is very strong but good thought. I wouldnt have thought of that. I will check the plugs and another clue. While trying to get it to run enough to back into garage it quit and took a lot of effort to get it refired. When it did i gave partial throttle for a while trying to get it to smooth out and while the idle was up it let out a hell of a backfire from the tailpipe i believe. Also a LOT of moisture out tailpipe. Not gas but looked a little oily. Posted using the Full Custom H.A.M.B. App!
All on my list now thanks. Gonna take some time since we just moved to a new house and getting settled in takes precedence. Posted using the Full Custom H.A.M.B. App!
Read all the replies. Here's where I would start. 1. File and regap points. They are a mechanical switch and that's really all that is needed for now. 2. New condensor. 3. Ohm out the coil, but for the cost I would just replace it anyway. In all honesty, if you left the key on, the coil definitely and most likely the condensor are dead. Not just replacing them is penny wise, pound foolish. Also, the coil is, literally, a capacitor. In my business, a leaking capacitor is a failed capacitor.
Is the coil mounted upside down? if its oil filled and mounted upside down the coil will get hot and eventually go bad, the oil is there to somewhat cool it. jeff
You got lucky...when the kids left the key on with my garden tractor, the coil actually exploded. I'd change it.
Big backfire, huh? Hmmmm. (the doctor says as he furrows his brow and rubs his chin...lol) Backfires can be caused by a few different things. If it's fuel-related, out the carb usually indicates a lean condition. Out the exhaust...usually a rich condition. A look at the plugs will tell all as far as fuel ratio. Black and sooty...too rich. Real white...too lean. Tan...just right. If they're black, they're probably just getting progressively more fouled...and that's why the engine is running progressively worse. It's possible that the spark isn't strong, and it's not burning the fuel as it should...which can mimic a rich condition. Look at the plugs, put a new coil on, check the health of the spark at the plug/wire connection, a new condenser if the spark is still weak. One thing we haven't considered is cross firing in the cap due to moisture or a bad cap. I have a feeling though, that after you put a new coil on, she might start purring again. Anyway...do all you can for the ignition system, including new plugs if needed...then check for a lean or rich condition. Check for intake leaks with some carb spray...especially at the base of the carb. Those small-base carbs on the old sixes tend to leak at the base. (a very small cross section in certain areas) You've got the right carb gasket with the notch or hole for the vacuum signal for the idle circuit? Make sure the choke is staying open. I'm not discounting the possibility that it might be starving for fuel. Bad pump, crap in the carb bowl clogging the jets, etc. Again, how the plugs look will give you a clue whether it might be running lean or rich. Well, I've suggested a lot of things, so I'll probably be right at least once...lol. Good luck.
I hope that you're not in any business where you work with capacitors, because then you would know that the coil is in no way a capacitor. The condenser is a capacitor, the coil is a step up transformer. AC 12 volts comes in through the switched 12v line that's generated by the points, thus behaving like AC and stepping up to the high voltage to arc through the spark plug gaps. As for what happened, the coil being a transformer, when DC is fed through it (because the points aren't breaking it into AC) it behaves like a wire instead of a transformer. So you were simply feeding current through it straight to ground. The heat was generated by the resistor dissipating heat and the wire dissipating heat (as they're not designed to take current like that). Having the coil mounted upside down where the oil was leaking out compounds that problem. As for the rough running, it doesn't sound spark related honestly. The coil or condenser may be toast but I kind of doubt it, they're fairly tough components and rarely fail. But there's an easy solution, check for spark! If it's good, move on, if it's not, sort it out. I'd make sure your timing is still good and the distributor clamp hasn't come loose or something. Check timing, check fuel, that's really all there is to making an engine run. That is, without worrying about more serious problems that could cause things.
An old dude once told me "90-percent of all fuel problems, are electrical." Have you accidentally left the key in the "run" position before? If you have, your coil is cooked. That it's leaking oil out the bottom guarantees it. I did the same thing with my '54 Buick...grabbed the coil and burned the shit out of my hand. It was my stick-shift hand, and I couldn't drive my Dakota home from the shop, so my wife had to get up, get the kid dressed and come pick me up at 3am. After the coil, I'd plan on a carb rebuild and check the fuel pump if the problem doesn't go away. That's why I like to put a glass filter inline between the pump and the carb, so I can always eliminate one thing right away. Also, check to make sure your distributor hasn't changed the timing on its own. Vacuum advance is good, the advance weights are still in place (the springs aren't broken), the hold-down clamp isn't loose, and there isn't too much play in the shaft. In fact, I'd check the distributor and timing before a carb rebuild. But definitely replace the coil. You cooked it. -Brad
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