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Coil test?

Phil705

New member
I thought I'd start a new thread and focus on some electrical issues. I put in a rebuilt carb, and replaced the ignition resistor in my 1972 Tucker. Tried to start it, and immediately saw sparks at the ingition switch and starter button. And noticed that a wire under the hood got fried. While the Tucker didn't start before, I did not have these problems. I may have caused a short in the wiring when I pulled off the dash, perhaps chaffing or a direct contact. Fuses ok, which seems odd.

Anway, I am checking the wiring (which is a mess) and replacing the ignition switch and starter button. Just curious: would a bad coil be part of the problem? How would I test the coil?

As always, thanks in advance

Phil705
Winthrop WA

ps Getting rain on our hard-won snowpack. Not totally a bad thing, as we need some snowpack consolidation, as long as we get some freeze and more snow. We had about 28" before the deluge.
 

cj7

New member
You can test to see if the cooil is working by removing a spark plug wire and inserting a screw drivier into the end of the wire. Place the screw driver near the block of the motor. Have someone crank the motor while you look at the spark jump to the block. It should look nice a strong (nice and bright) not weak (like it barly jumps).

However I do not think this is your problem.
What wire was fried under the hood?

Sounds like to me something is grounding out. Or possibly drawing a higher current than what it should.
I would look at all of your connections and make certain they are clean and are not touching anything. Look for any bare wires. Make sure your connections at the battery are clean also.
I would also check to see that everything is wired back correctly. You may have hooked something up in the wrong location?

Did the starter crank the engine over?
 

Catless

New member
Phil705:

It is possible to test a coil using a multimeter. If you don't have an auto-ranging multi-meter you will have to pay attention to what scale you have the meter set on. You will be testing for resistance (ohms). Unfortunately, you need to know exactly what coil you have as the specifications for coils differ from one another.

General tests include testing primary resistance and secondary resistance. To check primary resistance set up multimeter on low end of scale (if not auto-ranging) and on ohms. Remove all the wires from the coil (ignition off!). Touch one lead of multimeter to the + side of the coil and the other lead to the - (minus) terminal of the coil. Some general guidelines as to what you should expect to see are 1 to 2 ohms for a coil that requires a ballast resistor and maybe up to 4 ohms for a coil that does not require a ballast resistor.

To test the secondary side of the coil, switch multimeter to higher setting (if not auto-ranging) and place one test lead to the primary teminal of the coil (where the main wire big ignition wire goes to the distributor cap) and the other end to the - (minus terminal - the one that goes to the distributor body). You should probably read between 4.0 k ohms and 16k ohms.

I have guessed what coil you may have from an on-line WELLS Engine Management website (I picked several 1971 Plymoth vehicles with a 318 v-8). Their part# may be a C819 coil. Specs for this coil (from their website) show a range of 1.0 to 1.7 ohms for the primary resistance and 6.5 to 14.5 k ohms for the secondary resistance.

IT IS UP TO YOU TO DETERMINE WHAT COIL YOU ACTUALLY HAVE, however!!!!!!!!!!!!

Could you present a couple of photos of your coil, your distributor (with cap on), and distibutor with cap off?

Like cj7 asked, what wire got fried under the hood?

I have attached a few links to their website.

http://www.wellsmfgcorp.com/~wellsmfg/pdf/W1.pdf

http://www.wellsmfgcorp.com/~wellsmfg/ds_coils.php?coil=c819&submit=Submit

http://www.e-webcatalog.com/wells/ecatalog.aspx

Good luck. Keep us posted!

grd
 

fogtender

Now a Published Author
Site Supporter
You can also check the coil by putting a hot (12v) lead to the side that has the "+" on it and ground the side that has the "-" on it. Put a spark plug (or the screwdriver as described by cj7) into the spark plug wire coming off the coil and ground the spark plug to the neg side of the power supply. By touching and removing the power wire, there should be a spark.

That doesn't mean the coil is good though, it may work when cold and has it heats up in normal use, break down and cause the engine to act as if it had a bad carb. or fuel blockage.

I would first find out where the short is at that caused the current wiring to burn, I would doubt that is from the items that you changed out or worked on unless you did cause a power wire to ground out along the system (or may be the cause of some of the running issues that caused you to start working on it in the first place).

When I had my shop, I would find that people would bring their car/truck to me after they worked on it for a problem and created a couple of extra that weren't the original issue. But it makes for a lot of hair pulling to find them because each has a "Issue" that may not related to the other at all.

In a lot of cases like you are experiencing, when someone has a bad carb or ignition system, they crank and crank on the engine and burn up the starter motor for instance, but don't think that is related. Then the key switch will burn up and melt the wires because they put a bigger fuse (or bypassed it) thinking the fuse was the issue.... and so forth.

What may have started out as something as simple as someone left the key on and fried the points/electronic Ingition., becomes a nightmare of added issues...

Doesn't mean that is what your issues are, but if you can go back and start from the first issue, and rethink of all the steps you took, you may find out where the current issue is related. Like what was the reason you rebuilt/replaced the carb., was the engine not reaching max RPM, not starting, not running smoothly etc. All those "issues" can be related to other issues that are not carb related, just appear to be.

When people would come into my shop with a broke whatever, I would ask a battery of questions that may not have been related as far as the owner was concerned, but they are valid points because if I didn't know the car was just tuned up and now runs poorly gives me a place to look instead of just assuming the engine is in question.

Anyway, good luck and keep posting what you are doing in the hope we can be of any assistance.
 

Phil705

New member
The saga continues. I put in a new ingnition switch and starter button, replaced some suspect wires, and tried to start it. All I got was a "clunk" noise from under the hood, nothing like a cranking sound. But no sparks or shorts, and the lights work etc.

Went inside, had a couple drinks, pondered awhile whether to blow the machine up with me in it. Decided instead to try bugging you guys for any more ideas. I have not done the coil tests because I suspect that isn't the problem, unless you guys think it might be.

Phil705
Winthrop WA

Snowing again on top of concrete
 

Catless

New member
It's too early to celebrate but it sounds as if you have turned a corner.:clap: No sparks from under the dash is good!

The coil is not suspect at this juncture.

The "clunk" could be a starter solenoin engaging but not enough "juice" left for anything else........I'm just guessing here...........

How is your battery condition? You have been fighting this a while. Battery O.K.? Charge battery. Disassemble battery and starter connections and clean up with emory cloth, sandpaper or ?????.

Try again. Use multimeter to check battery voltage. What are the results?

grd
 

Phil705

New member
Success!!

Went out this morning, checked the battery voltage, it was 12.6.
Tightened the terminal nuts, killed a chicken, said some incantations, and tried to start it. Zoom! Started like nothing had been wrong. In fact, it's running much more smoothly, probably due to the rebuilt carb.

My guess is the original problem was a stuck float in the carb, then I fried some wiring when I pulled the dash. Once the wiring was fixed, the carb could do its thing. Took it for a four mile spin, and ran as well as ever.

Thanks to all of your advice and support! Especially: catless, fogtender, cj7, snowbird, Boggie, and all others who responded. You guys are first cabin!

Phil705
Winthrop WA
 

fogtender

Now a Published Author
Site Supporter
Re: Success!!

Went out this morning, checked the battery voltage, it was 12.6.
Tightened the terminal nuts, killed a chicken, said some incantations, and tried to start it. Zoom! Started like nothing had been wrong. In fact, it's running much more smoothly, probably due to the rebuilt carb.

My guess is the original problem was a stuck float in the carb, then I fried some wiring when I pulled the dash. Once the wiring was fixed, the carb could do its thing. Took it for a four mile spin, and ran as well as ever.

Thanks to all of your advice and support! Especially: catless, fogtender, cj7, snowbird, Boggie, and all others who responded. You guys are first cabin!

Phil705
Winthrop WA

Damn, I was hoping it was terminal so I could buy it cheap....:brows:

Well go play with your toy then....:w00t2:
 

Junkman

Extra Super Moderator
The saga continues. I put in a new ingnition switch and starter button, replaced some suspect wires, and tried to start it. All I got was a "clunk" noise from under the hood, nothing like a cranking sound. But no sparks or shorts, and the lights work etc.

Went inside, had a couple drinks, pondered awhile whether to blow the machine up with me in it. Decided instead to try bugging you guys for any more ideas. I have not done the coil tests because I suspect that isn't the problem, unless you guys think it might be.

Phil705
Winthrop WA

Snowing again on top of concrete

Whenever you hear just a "clunk" and the started doesn't engage, always check the negative battery cable first. Usually if there is a "clunk", then there is a poor ground in the system. If you don't get the "clunk", then it is usually a dead battery or a bad connection at the positive terminal. Also, make sure that you keep the top of the battery clean and dry. If it is moist, you will have a constant discharge between the two terminals, resulting in poor battery performance. Clean, dry connections are necessary to have a good electrical system. If the terminals have poor connections, this can lead to additional problems such as burned out alternator / generator, and burned regulator points, if so equipped.

Also, keep in mind that what sometimes appears to be a defective ignition coil can be a bad condenser in the distributor. The condenser in the distributor is there to absorb the excess current that is present when the points open. When the points are closed, the current is going into the coil, where this energy is being stored. When the points open, the energy is stopped, and the built up energy in the coil is released to the center electrode and travels to the center terminal of the distributor cap. From there, it is distributed to the outer terminal of the cylinder that is ready to fire. All this happens in milliseconds, so good clean connections are a prerequisite for the smooth operation of the engine. For good engine performance, you need good quality parts that can operate at peak performance under the adverse conditions of cold weather.
 
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