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Posted by: Amphicar770 Jun 24 2016, 02:17 PM

Per earlier post, picked up from shop today. Drove to work, running great. Driving home, running great although I notice volts reading less than 12v, temp gauge not working.

Almost home, a few blocks away. Going down hill. Huh, did engine cut out. Why, yes it has. Turn key. It cranks but no start. As if no spark or no fuel. Coil feels quite hot if that matters. By side of road now.

Posted by: The Cabinetmaker Jun 24 2016, 02:21 PM

Signs of a dying coil. They get hot and shut down. Cool off, and work...for a while.

Posted by: Amphicar770 Jun 24 2016, 02:22 PM

How long should I let it cool before trying again. Bosch Blue, not very old, is there a better option.

Posted by: Racer Chris Jun 24 2016, 02:26 PM

I've never had a bosch blue coil overheat and shut down.

Posted by: Racer Chris Jun 24 2016, 02:26 PM

Can you hear the fuel pump run for a couple seconds when you turn the key?

Posted by: Amphicar770 Jun 24 2016, 02:27 PM

Should it be hot to the touch?

Posted by: Amphicar770 Jun 24 2016, 02:36 PM

Yes

Posted by: Amphicar770 Jun 24 2016, 02:47 PM

What is easiest way to check for spark when stuck alongside the road. If someone comes walking by I can ask them to turn the key. Don't really have any tools with me but could walk home to get some.

Posted by: Racer Chris Jun 24 2016, 02:51 PM

Coils do get hot.

To check for spark, pull a wire from the distributor cap and hold it (don't hang on with bare hand) so the metal end is very close to the pocket on the cap, then crank.

Posted by: Amphicar770 Jun 24 2016, 03:12 PM

Thanks guys. I let it cool for 20-30 minutes and she started right up. Thoughts as to what's going on. Fuel pump is in front

Posted by: The Cabinetmaker Jun 24 2016, 03:31 PM

Go to flaps. Buy a momentary switch. Like the start switch in an old boat. Wire it up with long enough wires to reach from starter to engine bay with alligator clips on the ends. Next time it quits, hook the clips to the starter, turn on key, disconnect coil wire and using insulated pliers hold the end of the coil wire close to the sheet metal and look for spark while cranking. I've seen condensers cause this also

Posted by: Amphicar770 Jun 24 2016, 03:55 PM

Thx. No condensor. There is a pertronix, or similar, living under the cap.

Posted by: 76-914 Jun 24 2016, 06:22 PM

Your about the best natured man I've seen in awhile. I'd go ballistic after that bill you received. That's just me, anyway. What voltage are you seeing at the battery? Did the spade slip off the temp sender?

Posted by: cuddyk Jun 24 2016, 08:32 PM

Does sound like a bad coil...or an overheated one. Funny thing. I kept having similar issues with my car (running fine till coil gets nuclear hot, then dies. Cools off and starts fine again). I replaced the coil twice and still had issues until I added an additional ballast resistor before the coil. Now everything is great. I can drive the car for hours with no problem.The coil still gets hot...just not plutonium hot.

I know that the Bosch coils are supposed to have an internal resistor. So did the Accel coil which is specifically matched to my electronic ignition. But without the supplemental ballast resistor, it just got too hot and quit. Maybe someone here can explain it...or point me to another solution. I read somewhere that the need for a resistor on the Accel coil changes with the number of cylinders (less than 8 cylinders may need further resistance). That might explain it.

Anyway...

I agree that with the bill you just paid, they should sort this out no questions asked. And NO BILL!

Posted by: Racer Chris Jun 25 2016, 08:56 AM

I know Mallory Unilite modules had a tendency to make coils run hotter than points.
Idle rpm seemed to make the coil hotter than under load.
We had Mallory oil filled coils quit in the driveway a few times.

Perhaps Pertronix has the same effect.

Posted by: Racer Chris Jun 25 2016, 09:01 AM

While I questioned the time billed vs time required, there's no apparent relationship between the work the shop did on the car and the (ignition) failure during the ride home.
The shop shouldn't be on the hook to resolve this issue.

Posted by: Amphicar770 Jun 25 2016, 09:14 AM

Agree that I do not think the coil has anything to do with the work done.

I just read an article that internal ballast resistor coils indeed run much hotter than external resistor units. The resistor basically acts as a huge heat sink.

I wonder if the 914 would be better served using an external resistor unit?

Posted by: OU812 Jun 25 2016, 09:58 AM

One reason for this could be worn out spark plugs. Before the electric current is able to reach the spark plugs, it must pass through the ignition coil to ensure that the engine will start up at the minimum level of power or electricity. When the spark plugs are damaged or already worn out, they will basically force the ignition coils to work so much harder in terms of electricity flow. This will cause the coil to overheat.

Posted by: OU812 Jun 25 2016, 10:01 AM

One reason for this could be worn out spark plugs. Before the electric current is able to reach the spark plugs, it must pass through the ignition coil to ensure that the engine will start up at the minimum level of power or electricity. When the spark plugs are damaged or already worn out, they will basically force the ignition coils to work so much harder in terms of electricity flow. This will cause the coil to overheat.

This could also be caused from some sort of new resistance caused in the ignition wiring when the recent work was completed.

Posted by: McMark Jun 25 2016, 10:04 AM

You do know these cars are 40+ years old, right?

Posted by: injunmort Jun 25 2016, 10:17 AM

i would suspect coil as well. when cool the windindings are contracted and provide some continuity, when they get hot, they expand. if there is a break in the winding, you lose spark. after 40 years of heat cycling, it is not uncommon. also check for leaks from the coil, if they get real hot, they will leak. another indication the coil has packed up. good luck

Posted by: Amphicar770 Jun 25 2016, 11:38 AM

Plugs are new NGK, wires are new Magnacor's (8mm). The Bosch blue coil (epoxy filled not oil) probably 2-3 years old without a lot of use on it. Still, I have read several instances of premature failure on these (and the Pertronix Flamethrower coils as well). New coil arrives tomorrow. Hopefully just a fluke and not something else burning up the coil.

Posted by: OU812 Jun 25 2016, 11:52 AM

good luck, I wonder if there is a way to test it out, It would suck to buy a new coil only to fry it up and still not know what the issue is.

Posted by: cuddyk Jun 25 2016, 12:14 PM

Hi Mark. I didn't mean to imply that people shouldn't be paid for their work on cars that need constant attention. And, Chris...you are absolutely right that this issue is likely unrelated to the repairs. But that bill was definitely fat and Amphicar paid it with no pushback. If it were my shop, I'd recognize that this was a customer I'd want to keep happy, and with less than 50 miles on the odometer on the heels of a big bill, I'd fix a simple thing like a bad coil gratis. Or maybe just for the parts cost. Pretty sure you guys would, too under the same circumstances. But, then again, neither of you would've submitted a bill like that in the first place!

Posted by: Amphicar770 Jun 25 2016, 01:17 PM

Just a thought on coils. Would an e-core style HV coil, like a Pertronix 60130, make more sense. They certainly cool better and the resistance rating seems right. Any reason it would not work?

Posted by: Amphicar770 Jun 25 2016, 01:29 PM

Additional info from a, gasp!, Corvette forum ...

http://www.superchevy.com/how-to/ignition-coil-info/

from the above article:

"According to industry experts, coils have always had to compromise voltage output against current output. More voltage increases the initial ionization of the spark plug gap, but lowers the amount of current or heat that follows across the plug gap. When a coil is designed to produce more current, the voltage output generally suffers, which taxes the ease of ionizing the gap. In order to accomplish a combination of high voltage and current, the latest coils incorporate a special "E-core" winding design. This is an efficient design that more closely resembles the windings in a true transformer. In this system, less loss occurs during the transfer of electricity due to the closed core of the coil.

Given this technology, an "E" style coil produces spark with both high voltage and current. Another benefit is the coils run extremely cool, even at high rpm. This is due to the efficiency of the design, as well as the large laminations"

Posted by: injunmort Jun 25 2016, 04:12 PM

as an aside, according to a marine site, specifically regarding petronix and coils. it states that petronix recommends the use of an oil filled coil with their ignition. that it doesn't exceed 4 amp out or the risk over overheating coil and premature coil failure. to measure output, disconnect both sides of coil and measure resistance, then reconnect coil with ignition on, measure voltage at positive terminal of coil. divide voltage by resistance, this will give amps, which should not exceed 4 amps. if it does,you risk overheating coil. i would guess it would apply to epoxy filled coils as well. it goes on to say that by thier nature, electronic ignitions have longer dwell, which also heats the coil. hope this helps, search malonemarine ignition.

Posted by: catsltd Jun 26 2016, 08:58 AM

I wonder if your car has good grounds.
I know my car ran better once I put a ground to the engine,and replaced the chassis and trunk ground.
Never got above 12 volts until I replaced my original alternator though.

Posted by: Amphicar770 Jun 26 2016, 04:26 PM

Hmm, may not be the coil after all.

When I picked it up from shop I noticed voltmeter gauge was only reading about 10.x Volts.

After it died it had plenty of juice to crank the starter but when I got home and hooked up charger it confirmed 10.x volts and showed about 10% charged. After charging, it is back up and car Meter reads 13+ until I turn on the lights. The charger has an option to show alternator percentage and that is only at 25%.

I'll have to check at battery with voltmeter. Will confirm belt did not break but I am thinking it could be voltage regulator whic is original. I did have alternator rebuilt by reputable local shop before I put engine back in. Alternator wire harness is new as are the battery cables and ground strap at tranny.

Posted by: Shredhead Nov 8 2016, 03:03 PM

And the end of the story was...

Posted by: pbanders Nov 8 2016, 03:49 PM

I just scanned through this topic, and it reads like about a zillion "car died" or "won't start" thread. One observation (a possibly hot coil) gets turned into a whole explanation (despite his reading 12V or less before the car died), and it ends up probably being the charging system.

You have to be methodical when finding the cause of a stall or a no-start condition. You may think you know why, and you're wasting time checking mechanical, charging, fuel supply, ignition, and injection/carbs from a checklist, but it's the mechanic-proven way to diagnose and fix these problems.

There are a number of checklists you can find on Google, I'm working on one that's specific to our cars, that quickly verifies operation of each system so that you don't spend tons of time doing diagnostics. Hope to have it done in the next couple of weeks, we can review it here and make corrections/additions, and maybe we can make it a sticky that we can send people to when they have these kind of issues.

Posted by: pbanders Nov 8 2016, 03:53 PM

Strongly suggest you read this and follow the appropriate tests.

http://www.ratwell.com/technical/ChargingSystem.html

This excerpt in particular applies to your situation:

"Because we are so used to hearing about 12V automotive electrical systems, we tend to ignore the exact battery voltage. Take for example a battery that reads 12.35V. At first it seems to be in perfect condition (about 12V right?) but in reality a 12.35V battery is only 50% charged, 12.0V is 25% and 11.80V is completely drained. Whenever the battery reads 11.99V or lower it is basically a "dead" battery that has lost almost all of its charge. This will give you a rough guide to the state of charge (SOC)."

BTW, a fully charged battery is 12.76V, after you've dissipated the surface charge. Any voltage lower than that is telling you the battery isn't at 100%. You read a higher voltage when the car is running because the alternator is charging the battery (~5 to 10A).