Alternator

[Willy]

1041651

I own a Jeep CJ7 1983 with engine 6-258. Coil is getting hot and change location to the side instead the motor. Still coming hot. I read about alternative voltage should be null. I took a reading in AC voltage to the terminals of coil during idle and found 19 volts. Also between the output of the alternator with negative pole of battery was 30 volts. With DC voltage I read 6.3 volts to the terminals of the coil and 14 volts to the output of the alternator.

Any comment to this lecture? Is that the reason becoming so hot ? Where is the failure?

I will appreciate for your support

Willy[addsig]

 

[MudderChuck]

1041653

14 volts doesn´t sound like you have a bad diode or regulator. And 6.3 volts is right in the ball park for the plus side of the coil. The AC volts could be anything from a bad condesor in the radio to who knows what. Unhook tha condensor in the distributor, if present. Does your model have a double ballast resisitor? Hooking up the out leads backwords will cause the coil to overheat (but usually shows 14 volts at the coil). Most often it´s an internal short in the coil (or running a points coil, with a magnetic trip distributor) check the resistance (with the wires disconnected), from plus to minus (1.1 to 1.2 ohms), to ground (coil case after scratching) infinate (no reading), and from high voltage to the plus terminal and negative terminal and compare the resuts with a new (good) coil if available. Chiltons has a pretty good section on coil tests in the truck and van manual (in the older books). Hope I´ve helped some.

A dirty alternator (carbon dust) will often put out radio frequiency, that can be measured as AC with a good voltage meter. Doesn´t really count for anything though the amperage is just about zero.

If your coil checks out OK, have a good look at the ignition module. I´ve never seen an ignition module put out to much juice with the proper input, but I guess anything is possible. Usually puts out 6 volts with the key on, at the coil plus and 12-14 volts while cranking.

[addsig]

 

[Willy]

1041656

Thank you for your reply and support. I took readings :

Between coil terminals 1.2 ohms

Between high voltage output and any of the terminal coil: 10 kohm

Insulation between high voltage connector and ground: infinite as so terminals.

All wires disconnected

I checked any capacitor in the motorcraft distributor with magnetic coil, and was not any.

I claim to the technician who repair alternator .. regulator and bearings, he stated strongly alternator was in good order.. charging and voltage. The 30 volts ac cannot be produced in the alternator.

DC volateg acroos coil terminals was 8 volts during idle

Coil still getting hot

Another technician told me he checked any ac voltage in another similar car, and was none

Any comment?

I will appreciate very much.

[addsig]

 

[MudderChuck]

1041683

I´ve found stray AC in some electrical systems that never really seemed to hurt anything. It could be thirty volts AC with no amperage, in that case irrelavent. Or it could be leaky diodes in the alternator, which are a pain to test. About the only other test I could think of that might help, is running the plus cable to the coil with a amp meter (in series) and comparing with a healthy car. With only an ohm of resistance there has to be a pretty healthy current flow (measurable) in there.

One other thing you might look at is the wieght of the coil, if the oil has leaked out it might over heat.

I´d really like to hear the solution to this one.

Usually when there is a bad diode, the voltage drops about 4(3) volts. Max output of the alternator is supposed to be 16/17 volts. If you have a delco alternator there is a test hole on the back, when jumped with a screw driver gives max voltage (16) that will let you know if the regulator is messing up or the possibility of a bad diode. But to tell you the truth I can´t see how a bad diode would overheat the coil.

The ignition control module is really nothing but an amplifier, I guess there exisits the possibility of AC volts. But DC volts (amps) make alot more heat than AC volts, and if the AC was anything more than radio frequiency, would have a tendancy to cancel half the wave. The end effect would be no real increase in amperage. If there is a hole in my logic let me know. Most of my electrical knowledge is with houshold current (theory) though I have been the last mechanic to look at an awfull lot of cars.

Most of the over heating coils I have seen, had an internal short (between two coils) and often, eventaully burnt through the side of the coil, covering everything in some really stinky stuff.

I also seem to recall, there is a resistance wire between the igniton and coil, but it´s usually a good or bad (spark no spark).

Arching across the top of the coil, or a leaky wire will also cause overheating, but is usually accompanied with a pretty heavy missfire.

Ran out of possibilities for now will give it some thought.

[addsig]

 

[MudderChuck]

1041687

Thought of another possibility. Unmount the coil and wrap it in a rag, test the case to ground ( volt meter or trouble light, at the highest volt setting first) after scratching a bare spot, with the motor running. Could be the secondary (high) is arching to the case some (a leak) then to ground (usually indicated by a mostly yellow high voltage spark as opposed to a mostly blue healthy spark). Could also try positioning the case (bare metal) 1/16 of an inch from a good ground and check for arch with the motor running. Be careful about grabbing the coil with it dismounted, could be a hair raising exsperience. Sometimes (due to moisture, or bad primary cable) the top of the coil gets etched with a carbon trail, which can heat things up. Let me know how things work out. Could be a short only at high voltage with the motor running (could account for the AC readings your getting, but you´d have to have a heck of a meter to measure so few hertz).

Which kind of control module do you have? Inside the distributor or outside? The ones inside, are a little pricey and can be damaged with an ignition short. The external ignition modules are pretty much a dime a dozen at most junk yards. The Dura spark II was used in a whole bunch of ford products, the Dura spark III had a history of control module failure and are hard to come by, except at a parts store.[addsig]

 

[Willy]

1041703

Yesterday was really bad. After filling gas to full level, I drove for 14 kilometers with out any problem, with more than 3 stops. When I was driving home, started problems. Engine stop suddenly, precisely on the cross so I had to use starter to move the car. The coil was very hot, almost new one.

Wait for 5 minutes and starts again but very low rpm. Drove 3 blocks and again. It tooks 2 hours to get my parent's home, just 4 kilometers. Today the man who did the tune up exchange 4 coils. Nothing. Checked spark from the coil to ground, the spark arriving to the spark plug, feed +B from battery to the coil, gas was going to the carb and smelled. He tried with carburator cleaner to boost , dismounted distributor to see if was in timing, NOTHING. Of course each time using starter. Until battery start showing low power. After several hours we decided to request a crane to sent to the service car station. I hope tomorrow to know what could be. To avoid problems with alternator, I disconnected the connections and to isolate. But all was the same.

There is no explosion. So the only thing not done was to exchange spark plugs and use another gas. The electronic module is sealed but we seem is ok otherwise would not produce spark.

If someone can support with suggestion , I will appreciate very much.

Tomorrow I hope to receive better news.

Regards and appreciated your cooperation

Willy

[addsig]

 

[MudderChuck]

1041720

Sounds like it´s time to start over again and start with the basics.

Clean the battery cables at the battery. Grab every wire leading from the battery to whereever and check for tightness.

Take a look in the distributor and check for corrosion, the carbon contact in the cap and the rotor, for cleanliness and scorching.

Pull a couple of plugs and check the color. If possible take a look in the sparkplug holes, where you can, with a mirror and flashlight (I´ve seen water in there). Blowing a little air into the spark plug hole and holding a paper towel close will sometimes show water, coolant or moisture.

Check the resistance of your coil high voltage wire and compare with another of about equal length.

Blow out the distributor with air, under the trigger mounting plate also.

Sounds like it could be a head gasket leak but you haven´t said anything about the motor missfiring. Sometimes the misfire is pretty subtle.

when you get the motor going again, check the radiator for bubbles or foam (does your Jeep us a little water). Take a look at the exhaust pipe, a little moisture at sart up is normal, but when it continues at operating temp. is an indication of head gasket leak.

I honestly don´t know if there is a thermal protector in the control module, but if there is it could account for sometimes running and sometimes not.

A head gasket leak, will often leave the plugs with a funny color usually reddish, not white gray or black. Oil buildup is usually black clumps on the plug.

The reason I´m thinking head gasket or wet distributor is this could account for a very hot coil due to the loss of resistance (which can be damaging to the control module).

Had one Duraspark three sytem (Bronco) that had a reversed run and start lead to the control module which would overheat the module and cause it to fail and would overheat the coil. But we already looked at that, 6 volts run from + coil and 14 volts from plus coil while starting.

High voltage leak or lack of resistance is my best guess.

The starting relay is also part of the ignition system and when cruddy inside or full of water will cause some strange problems. The case can be opened, carefully for a look by bending back the tabs on top, but just open it a crack. It has a tendancy to break, really not made to be serviced. The starter relay isn´t sealed very well, a little compressed air around the edges might blow some moisture out.

If it was easy it would already be fixed.

[addsig]

 

[Willy]

1041740

Thank you Mudder Chuck. Your tips I will keep to future problems because most of the recomendations were done byt he technician and I learned a lot.

The car it s said , started with a diferent electronic module. That was the reason. We did not take care because spark was reaching to the cylinder and was new. But the technician told me he just tried with another ignition module and was starting with the coil also new. I asked what manufacturer was and told me just numbers and any amrk.

I called inmediatly the guide sold me and promise on monday to replace the module with so many sorries. I asked if was duraspark, but he just told me was a last one he had in stock.

Wich mark do you recomend? I read something about distributor of F-300 ford truck 1982.

have a nice week end. Thanks God this do not happened off road . I was plannig to go desert places

regards

Willy [addsig]

 

[MudderChuck]

1041756

Over the years Jeep has had everybodies distributor in there from AMC, to Ford through GM to who knows what (maybe mercedes next). It can get confusing, the HEI GM works well in none regulated carburator models, but I only remember seeing it on some AMC V-8´s. The AMC is a little tempermental, the Dura spark II (or Duraspark II knock off) seemed to work well.[addsig]