bad coil?

Post the year make model engine etc.

not necessarily. my car is 15 years old and has never, to my knowlege, produced anything but a yellow spark.

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If the coil can produce a spark (assuming you tested it hot & cold) that jumps a half inch, it's NOT your problem. If by chance you are dealing with a breaker point ignition, go after the condensor.Good luck.

'66 pontiac lemans with v8 326.

That is a symptom of a dead condenser.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

gravity wrote:

gravity wrote in rec.autos.tech

Start out by replacing the points, condensor, rotor and cap. They should be replaced whenever you do plugs. Might also replace plug wires. If you are getting a half inch spark of any brightness from the coil it is probably good, after all that is .50 and your plugs are gapped at .035, a lot smaller than half an inch. if a plug opens to anything approaching half an inch it is not going to fire.

thank you all for your comments. I do have new points, condenser, rotor & cap. The plug wires were replaced last fall. I am beginning to lose my temper with this car.

after posting my previous message about an orange/yellow spark from the coil I went out today and wanted to test it again. Now I get NO SPARK at all. I swapped out the coil with a new one, and still NO SPARK.

I know that I have twelve volts goint to my ballast resistor, but when I take a reading from my positive terminal on the new coil, I only read 5-6 volts. Is this usuall or should this be higher? What am I missing?????

Any assistance is appreciated. Thanks again.

A ballast resistor on a GM ?? If you only have 5 or 6 volts on the hot side of the coil, this seems low. All the GM's I've seen from those days were internally resisted coils run from 12 volts & knocked down to about 9 with the coil. Ditch the resistor ,I don't think it belongs there, make sure your coil is internally resisted (it should be marked), put in your new points/condenser & go. Good luck.

That seems low to me, I would expect to see 8-9V at the coil. I assume you're testing this while cranking, since if you have no spark the engine obviously isn't going to start. Usually there is a bypass wire from the starter solenoid to the + side of the coil (or the coil side of the ballast) and that should read battery voltage when the starter is engaged. something like 10V I would expect (since the voltage is going to drop due to the starter being engaged.)

good luck

nate

gravity wrote in rec.autos.tech

GM's, AFAIK, did not have ballast resistors in the ignition system. Only Chrysler used them. Apparently simply for the purpose of making an interesting problem to troubleshoot. Other manufacturers had them built into the coils. Ok, it won't start, you have low voltage at the coil, and apparently no spark. Check all the wires, make sure that they are all intact, not shorting, and have a good solid connection at every point. From the ignition system, to the coil and to the points. Be sure to check that the ground is tight also. And go back to the distributor and make sure that the points are set properly, and that the screws holding everything down are tight. You may want to just buy a new capacitor. I had a motorcycle (with a separate ignition system for each cylinder) that had one cylinder that fired intermittantly when cold, and not at all when hot. Turned out that an almost brand new capacitor had failed by shorting internally. Sound like your problem? Low volage is caused by a bad connection, or a partial short. Of course, the short could be inside your coil, in which case you simply need to replace the coil.

Bad condenser right out of the box is one guess.

I have seen that before and that was when points and condensers were still in mass production. Who knows what 20-30 years of sitting on the shelf will do to them.

I have also seen the ground on the distributor fail giving a weak orange or no spark. You can use a booster cable from the battery neg to the distributor itself to check that.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

I have checked all the wire connections and can't find anything wrong with them. Retracing my steps, the only changes in the equation between when I was getting spark (yellow/orange) and not getting spark is the changed points and condenser.

If the condenser is shorted/faulty, could this cause NO SPARK aty all from the coil?

I supppose that all I have to lose is the time it takes to replace the condenser with the previous condenser or get yet another new condenser and test for spark again (which requires pulling the distributor AGAIN.....aaaaargh!)

Any comments are appreciated. TIA

gravity wrote in rec.autos.tech

Yes. Because the condensor stores a charge of electricity, while one side is grounded. If a condensor shorts out it the hot side will run directly to ground, stopping the coil from working.

Really? Why do you have to pull the distributor?

There you go with my bad ground statement, you messed with the distributor ground. The hold down foot on the distributor is the ground for the points and condenser.

If it is rusty or the bolt is rusty or the rim of the distributor base is rusty you can have a partial or no connection situation. I would try the booster cable from the battery to the distributor before tearing it back apart. You might just need to clean the foot and bolt.

But Yes, a condenser shorted can cause no spark. I have also had the stupid screw not be tight enough because I was worried about stripping it and had the points just slip open when they spun....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Had a similar problem with my (1976) CJ-7. I followed the electrical diagrams and one of the first "stops" along the electrical path was the alternator. OK, so I replace it and the CJ started and its still running (eventhough I no longer own it). -PapaRick.

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gravity wrote:

That is a thought, if those GM alternators short internally they can ground the power wire to the coil cutting out the spark. They tag coil power for the excite wire.

You could just unplug the thing to test it.

Mike

Rick Colombo wrote: