frying ignition coils

[Donald W.]

The car developed a severe miss that tended to for the most part to sort itself out as it came up to operating temperature, still a little miss at idle and down on torque. Problem came on about 25 miles after I filled with gas so I was thinking bad gas.

Anyway I started off with dwell and timing and threw in a new coil for good measure. That didn't help. Then I put in new fuel filter, pcv valve, and replaced the fuel that was in the tank. Simptons persisted but I got on then freeway for a good blow out and the car came alive and felt good. Near home I mashed the pedal and was getting near 4800 rpm when the car quit like I had turned off the key.

Got the car home and found the new coil to be bad (it won't throw a spark when I crank the engine) and the contacts on the points in sad shape, one completely gone. Put the old coil back in with the same no spark result.

Secondary resistance of the 2 coils is very high, I don't know if this is normal. I am having fun!

[HOTROD64-STOCK69]

Hi Don, measure the voltage to the coil when the key is on. See if its over 9VDC. Your symtoms sound like to high of voltage to the coil. The stock in harness resistance wire may not work anymore. You may have to add a resister to the wire or go to a breakersless like Pertronix. I thought you already did that? If you did hopefully you connected the red wire to 12VDC and the coil still was resistered down to about 6VDC. I just did two systems that I had to follow the ignition wire back into the harness and find where the resister wire started and splice just before it starts for the positive (red)wire. I believe the color you are looking for is purple. Then the harness will look more stock. PM me if you want to chat about it. Just one idea, Mike

[Donald W.]

Hi Mike, Thanks for the response. I'll PM you.

[HOTROD64-STOCK69]

PM replied

[Donald W.]

I've given up on the fried coils threory. Still having spark issues but I think that the coils are ok. That theory was sparked by the high resistance values that I read on the coils. The 5 or 6K ohms that I was reading at the post are normal. Live and learn. Now I'm wondering if I should not be using radio interference resistance wire for the coil to dristributor lead. Sounds like a long shot even to me.

[Mark B]

Have you tried replacing the condenser (capacitor) in the distributor? I've had those go bad and cause like symptoms. It's a cheap trial. If it were me I'd just replace both the points and condenser. You said one of the contacts was gone so I assume you did replace the points already, but did you replace the condenser? Also check the cap for carbon tracks from the contacts. A point system is pretty basic, should be an easy fix once you narrow it down.

[HOTROD64-STOCK69]

Donald,
You do understand that you do not have to crank the engine to test for spark, corrrect?
Just pop off the dist. cap and with the key on put a small screwdriver into the points and wiggle them open while holding the high voltage lead (coil wire) close to a ground source. The coil will throw a spark if it, the points and condenser are good. Go electronic. Yes the radio noise suppresion wire should be replaced with a good multistrand wire until you are successful. Mike

[Donald W.]

Thanks Mark. Relaced the pionts the other day. Put in a new condenser today and tried to start the car, and it didn't. Then I got busy watching TV and will give it another round tommarow. No obvious signs on the distributor cap but I cleaned it up some with some Q Tips. -Don

[Donald W.]

Mike, I didn't understand that untill someone pointed it out to me a few days ago. Method that I used was alligator clip leads to tap the negative side of the coil too ground while checking for spark to ground from the coil lead. I got just the tiniest bit of spark a few times that way. -Don

[HotRodTodd]

Hi, just joining in the conversation here, but you may have had a shorted condenser and damaged your new coil in the process. Good replies about voltage to the coil (can't be batt./charging voltage), and the condenser. The damaged points are a dead giveaway. You can check for spark either way (opening the points with the key on or the alligator clip), but just using a jumper wire to the coil only tests the coil and it's power supply - not the rest of the circuit (points, cond. wiring). Make sure the ground wire inside the dist. is in good shape (grounds the advance plate the the dist. housing) and make sure your dwell / point gap is at least close (final adj. while running with an allen wrench). Also, no dirt or grease on the contacts! Tip from the old days - use a dollar bill to clean new points...with the point rubbing block on the flat side of one of the cams (points closed), insert a dollar and pull it through. With the key on and points closed, open points with a non-conductive tool and watch for your spark from the coil. Another tactic is to use a test light (a real test light and not an LED style) on the neg. side of coil while engine is cranking - the light should flash on and off (as the points open and close) - this should happen at the same time as the good, blue spark.
Hope this helps, and if there's specific questions, let me know
Todd

[Donald W.]

Hey Todd thanks for all the nice tips. I think that I have done all except for the dollar bill and the continuity test flashlight. Used to have one of those but it disappeared somewhere. Checked distributor to engine ground visualy with an ohm meter. Basically I worked my self in circles untill I came right back to bad coil. Picked up a good stock replacement at Napa yesterday and will give it a try today. Also got a feeler gauge to replace the one that went away with my stolen tool box so I'll get a good set on the points contacts. New points and condensor are in waiting for the coil to work. -Don

[Donald W.]

Still dinking around, new coil puts out a nice spark but car didn't start. Tested for spark at plug end and got none, went back into the distributor and found something that I don't understand. Using the beeper on my meter I found that I have a ground path from the hot wire terminal to engine block with the points open. If I disconnect the wire that goes thru the firewall to the ignition switch the ground disappears. To my thinking, with the key off I shouldn't show a source to ground. Should I ?

[HOTROD64-STOCK69]

You didn't explain how you achieved spark. Did you replacethe smoked points? Even if they will let you see spark by 'shorting' them they still may not work under cranking conditions. think in simple terms. The continuity reading could be unrelated and be as simple as a filiment in a light bulb. Did you know on the '64 gto the brakes lights only work if the ignition is on?

[Donald W.]

Points and condensor are new. I achieved spark by pushing the points closed and holding the coil output 1/4" from ground. Yeah I have been going in to many directions at once, needed to step back. If I hook things back up I should have 12V at the coil as before, and continue process of getting spark out to the plugs. Thanks

[Donald W.]

End of the drama. THE GOAT RUNS.

[HOTROD64-STOCK69]

Donald,
Glad to hear you got her runnin'. A couple things to ponder here though...The coil sparks when the points open...when they are closed it is shorted to ground. second check voltage to the coil when the engine is running, if it is above 10 volts add an external resister before the coil wire that comes from the firewall. Even if you have voltage below 10vdc and add a resister it will still work and not drop the voltage too much. Mike

[Donald W.]

Coil sparks backwards of what I would have thought, knew that points closed was ground to distibutor plate.

Using my new digital VOM, I read 14.35v across the battery (Maybe charging voltage): ballast resistor in = 14.31v : + coil (ballast resistor out) = 10.36. Added new more ohm's ballast resistor before engine start. I will work on getting the coil voltage down. Thanks for the numbers and your help in general.

Don

[Donald W.]

Car is running great. I even finished that pedal mashing shift into 2nd gear that was the start of this thread. Nice tire chirp and front end lift on that shift. Now that it is out of my system I'll be nicer to the drivetrain for a while.

Thanks again for all your well thought out comments. Me being me I can tend to skim the surface of what is being pointed out and not pick up on the details. Sometimes you get lucky, other times the details are where it is at. Anyway I've spent some time going over the electrical schematics for my year GTO and discovered that there is actually decent logic to how the engineers drew out those plans, and to the sequence of trouble shooting tips presented in the manual. In short, pay more attention Donald!

[Mark B]

Glad to see it all worked out.

[Donald W.]

Car was running so good. Now number 8 cylinder is not firing. Different plug wire got it to fire some. I'll take a look at the plug tomarrow and go from there.

[HOTROD64-STOCK69]

Car was running so good. Now number 8 cylinder is not firing. Different plug wire got it to fire some. I'll take a look at the plug tomarrow and go from there.

I seem to recall those wires were kinda old and used up, correct? That old Poncho NEEDS good reliable ignition to make the car purr. Sounds like new plugs and wires are the order of the day.

[Donald W.]

I seem to recall those wires were kinda old and used up, correct? That old Poncho NEEDS good reliable ignition to make the car purr. Sounds like new plugs and wires are the order of the day.

Eight new Champions and some Napa wires has the Pontiac purring again.

Number 8 plug was wet and gunky. I replaced plugs and wires a while back but was never happy with the wires. So all new stuff now.

[HOTROD64-STOCK69]

NAPA makes a nice wire.

[HotRodTodd]

No Champion plugs!! Hate 'em with a passion..give it what it wants - AC Delco...:cool:
Todd
PS Good to hear it's running good.

[Donald W.]

No Champion plugs!! Hate 'em with a passion..give it what it wants - AC Delco...:cool:
Todd
PS Good to hear it's running good.

Bad experience with the Champions or just general principals that you don't like them. Are the AC's available localy. I went to Napa and my choices were Champion, NKG, and Autolite.

[HOTROD64-STOCK69]

Carquest carries AC. It probably doesn't matter what brand of plug you use in your case. Since it is the back plug that was bad it's possible it is due to worn valve guides anyway.

[Donald W.]

Carquest carries AC. It probably doesn't matter what brand of plug you use in your case. Since it is the back plug that was bad it's possible it is due to worn valve guides anyway.

Someone outside of this forum suspected valve guides also. If that is indeed a problem he suggested that I might just be able to replace valve guide seals.

[HOTROD64-STOCK69]

You can on the exhaust valves with boot seals. The intake guides are not cut for them so you can only replace the 'rubberband'. Unless you pull the heads and cut down the guide. I have the tool for removing the spring so we could replace the exhaust seals. I have the seals also. You up for it?

[Donald W.]

Sounds like a good plan Mike. Timing I guess would depend on the weather and your shedule. We could work out the details via pm/phone. Ok?

[Donald W.]

You can on the exhaust valves with boot seals. The intake guides are not cut for them so you can only replace the 'rubberband'. Unless you pull the heads and cut down the guide. I have the tool for removing the spring so we could replace the exhaust seals. I have the seals also. You up for it?

I say matey, appears to be nice weather a comming on yonder horizen.

[HOTROD64-STOCK69]

I found the seals, they even have the teflon inner liner and I have the 'rubberbands' for the exhaust plus the cork rocker cover gaskets. All is in place now except time. I found out today that Chuck's '65 needs new lifters so I ordered them up but won't get to the work until next week because of the holidays and my boat work schedule. Be patient and it will all work out for the best. I also lost one of my dogs to a nerve disorder similar to ALS so with the holidays, work, and a death in the family it really slows down my hobbyist work schedule, rats!
Merry Christmas to all, too!!

[HotRodTodd]

but, yes Champion plugs have bit me in the a#%, especially with GM engines. They tend to foul out easily. If it's a valve guide problem, typically it will smoke (blue) after sitting a while and/or cold. The indication on the spark plug in question will be heavy deposits (sometimes it looks like the Elephant Man!) all over the ground electrode. This is when the plug stops firing. If you don't have these symptoms, you may want to investigate further. BTW, usually an alternate "umbrella" type of valve seal is available an does a good job until you eventually pull the heads and do the guides.
Todd

[Donald W.]

Smoke is not a real problem but your description of the spark plug was pretty apt.