ignition system voltage question

[Anonymous]

With the help from the forum, it looks like my engine is not turning over because of an ignition system problem (tested for a spark with the coil wire and there is none). I replaced the coil and still the same problem, cranks but won't start. I got a multi-meter and tried the primary circuit test per the shop manual (connected the leads to the battery and the coil). The voltage indicated .08. The shop manual says if it is 6.9 volts or less it is ok. My question is what is the correct range, .08 seems way too low? Also, one more question, the coil has a positive and negative post, does the wire coming from the battery connect to the positive post?

 

[Lazy JW]

Not sure what vehicle you are working on, so I'll discuss a breaker point system first. The coil needs adequate voltage to work properly. .08 volts isn't even close. On a twelve volt system without ballast resistor, you should see 12 volts at the positive terminal on the coil. With ballast resistor it should be around 8 volts or so. Connect the negative voltmeter lead to the negative battery terminal, and the positive lead to the positive terminal on the coil (ignition switch "on"). If that shows nothing, then try hooking a jumper wire from the battery to the coil and test for spark.
Joe

 

[Anonymous]

The (+) positive terminal should be connected to the ignition switch possibly with a Ballast resistor between it and the switch as Joe mentioned.

 

[Anonymous]

OK, I connected the negative voltmeter lead to the negative battery terminal, and the positive lead to the positive terminal on the coil and it indicated 12 volts. This is a 66 Mustang 200ci I'm working on. Doing the test per the shop manual (connecting the red positive lead to the positive battery terminal and the black to the positive terminal of the coil yields .08 avg. For grins, I took a 12 gauge wire and connected the positive battery terminal to the positive coil post. Unfortunately, there is still no spark from the coil wire. This is a new coil just bought last Saturday. Any other suggestions as to what is what with the electrical is greatly appreciated, I just have little to no knowledge of electrical systems and this is frustrating me. Thanks in advance.

Mike

 

[Lazy JW]

Mike,
The test that you described only shows the voltage drop between those places. Don't worry about it as it is pretty much useless for our purposes. The important thing is that you do have 12 volts to the coil. Now, in order to make a spark, the current must first flow through the coil, through the points, and then to ground. When this happens, an elecro-magnetic field builds up in the primary windings of the coil. Then the points open, breaking the circuit (hence the name "breaker points). When the points open, current stops flowing, and the electro-magnetic field collapses, which induces a voltage in the secondary windings of the coil. This voltage is MUCH higher than the primary voltage, and it builds up to a high enough level to finally jump the gap at the spark plug. That is how the system works. So now you need to see if you have continuity through the coil by checking to see if you have 12 volts at the negative terminal of the coil. You may need to unhook the wire from the negative terminal. If you have voltage coming through the coil, leave the wire off of the negative terminal, and hook a jumper wire from the negative terminal to ground for a second, then remove it. You should get a spark when you remove the jumper. If not, the coil is bad. I have seen brand new coils that were no good. If you do get a spark, then you need to verify the continuity through the points to ground. With the ignition off, use the ohm function of the multi-meter to check from the negative terminal to ground. You will need to rotate the engine slowly by hand to get the points to open and close. When the points are closed there should be a direct short to ground. As they open, the resistance should go to infinity. That should keep you busy for a while.
Have fun,
Joe

 

[Anonymous]

Thanks for the suggested actions, I'll try those tonight. I feel like I'm getting in too deep here. Are there any good, easy to understand books on auto electrical systems that the forum would recommend?

Mike

 

[Anonymous]

maybe I missed it but have you changed or checked you voltage regulator.

mike

 

[Anonymous]

I have not touched the voltage (alternator?) regulator.

Mike

 

[Lazy JW]

The voltage reg/alternator is unrelated to the no-spark problem. If the charging system is bad the battery will simply go dead after it has run for a while.

I know this all seems overwhelming at first, but if you take it slow and just do one thing at a time we will talk you through it. The best book I have ever seen is my old, tattered, "Basic Ignition and Electrical Systems" by Petersen Publishing. I'm afraid that it is long out of print, however, but you may find it used somewhere.
Joe

 

[Anonymous]

Since you have a voltmeter, here's a simple way to test for good points (or not): connect the BLACK lead of the meter to the battery (-) negative terminal (or to the engine block, which is the same). Then connect the RED meter lead to the coil's (-) terminal, which is connected electrically to the points.

Now, put the meter where you can see it from inside the car and crank the starter. You should see the meter jumping back & forth between about 8 volts and 0 volts while cranking. This will tell you that the points are working (at least), and that the coil is OK, at least OK enough to make sparks.

Check back with us after this test, let us know what you see.

 

[Anonymous]

Ok here are my results from the above suggestions
"So now you need to see if you have continuity through the coil by checking to see if you have 12 volts at the negative terminal of the coil. You may need to unhook the wire from the negative terminal. If you have voltage coming through the coil, leave the wire off of the negative terminal, and hook a jumper wire from the negative terminal to ground for a second, then remove it. You should get a spark when you remove the jumper" - Used 12 gauge wire and attached to negative terminal and touched the block, I do get a spark.

With the ignition off, use the ohm function of the multi-meter to check from the negative terminal to ground. You will need to rotate the engine slowly by hand to get the points to open and close. When the points are closed there should be a direct short to ground. As they open, the resistance should go to infinity - I am more than likely not doing this right, but trying 2000 and 20k on the ohm meter, it stays at 1 and does not move when I turn the motor by turning the fan.

Since you have a voltmeter, here's a simple way to test for good points (or not): connect the BLACK lead of the meter to the battery (-) negative terminal (or to the engine block, which is the same). Then connect the RED meter lead to the coil's (-) terminal, which is connected electrically to the points. Now, put the meter where you can see it from inside the car and crank the starter. You should see the meter jumping back & forth between about 8 volts and 0 volts while cranking. This will tell you that the points are working (at least), and that the coil is OK, at least OK enough to make sparks. - initially the volt meter reads 11.95 and then I crank the starter with a remote starter, the volt meter drops to about 8.5 and stays there, it does not move to 0 and back.

 

[61Futura]

Sounds like your points aren't closing or they have burnt contacts. Or the wire from the coil to the points is bad (open). There should be a small ground strap from one of the points mounting screw to the body of the distributor which you should check to see if it is there.

 

[Lazy JW]

It's time for a new set of points. Go ahead and replace the condenser also, they rarely go bad but this isn't the time to learn how to tell for sure. If you have never done this before we can walk you through this also. But first, check the wiring between the negative terminal of the coil and the points. Using the lowest setting on the ohm meter (X1 or X10) check for continuity to the place where the wire hooks onto the points. The meter should show zero resistance. Then, with the points closed, check the resistance through the points. They should read zero also. Then check the grounded side of the points to ground. This MUST be zero resistance. You are getting close now, you have power to the coil, and also a good coil, now you just need a switch to turn the power on and off. That really is all that the points do, just like you did with the jumper wire, only the points do it a LOT faster (and at the correct intervals).
Joe

 

[cdherman]

One issue here -- Marmese said he got a "spark" when he touched his negative terminal jumper to the block. I have the feeling he was talking about a spark literally at the point where the negative jumper was touching the block.

If the coil has enough continuity (low enough resistance) to give a spark at the negative terminal when you jump it to ground, I *THINK* that may mean his coil is bad.

The "spark" Lazy JW was talking about was a spark across a plug gap I think, which the coil should release when the neg jumper to ground is removed or "broken".

Concept: The plug fires when the points OPEN, not close. This gets lost frequently I suspect.

If the full voltage of the spark was going through the points it would burn them up in minutes, or get them so hot they would fuse together. And besides, 12v won't jump a large enough gap to produce reliable ignition.

The coil is a big capacitor or "storage tank" for eletromagnetic energy or just plain "electricity". JW gives the correct explaination, but try to simplify in my mind. Its a tank -- it fills up with electricity (points closed), and when the electricity stops (points open), it comes out (FAST).

Hope I havn't made things worse here, with my non technical explaination. I might be a little wrong as well, but I am concerned we have decided maramse has a "spark" from his coil when he may not.

 

[Anonymous]

The coil is a big capacitor or "storage tank" for eletromagnetic energy or just plain "electricity". JW gives the correct explaination, but try to simplify in my mind. Its a tank -- it fills up with electricity (points closed), and when the electricity stops (points open), it comes out (FAST).

Hope I havn't made things worse here, with my non technical explaination. I might be a little wrong as well, but I am concerned we have decided maramse has a "spark" from his coil when he may not.

A coil and a capacitor are two completely different things. The coil steps up the battery voltage, 12 volts, up to several thousand volts, depending on the type of ignition system. Also, electromagnetic energy and electricity are different things. Electromagnetic energy is a result of changing current in a conductor.

 

[Falcon62]

A coil and a capacitor are two completely different things.

And a capacitor will store energy, a coil will not. With the ignition off, there is no "energy" stored in the coil. If you had a capacitor the size of your coil, it would store enough energy to hurt whatever body part provided a path to ground!

 

[Lazy JW]

The point that Cdherman is trying to clarify is that maramse may not actually have a good coil. Indeed, the spark needs to be generated in the secondary windings of the coil and will be manifested at the spark plug.

When I went to avionics school in the Marines, we were taught that whenever current flows through a conductor, electromagnetic lines of flux surround the conductor and expand until the current ceases to increase, at which time they stabilise (this is known as saturation). When the current stops flowing, the lines of flux collapse, which induces a current in the conductor. When this occurs in close proximity to another set of windings (i.e. the secondary side of the coil) then a current will be induced in that set of windings also. This current will have a relationship to the number of windings in the secondary (more windings = higher voltage and lower current). If someone can PROVE what the relationship is between magnetism and electricity, they will be a Nobel prize winner instantly.
Joe

 

[Anonymous]

cdherman is correct. The spark I was talking about was the spark at the block from the jumper wire. I actually replaced the points already anyways. Unfortunately, trying to start with the remote starter all I get is clicks from the solenoid (this I assume means a bad starter). But back to the point of the coil, is this indicative of a bad coil then and do I need to replace it? Another point, I eventually want to dump the points ignition and go to a Duraspark, would you guys recommend just trashing the distrubitor right now and go with the Duraspark; and if so, where is the best place for directions on install? Thanks again for your help, it has saved me 600.00 by me canceling the order for a Painless wiring kit.

Mike

 

[Lazy JW]

Sorry about that, I assumed that you would know that I was referring to a spark generated at the plug. Try the test again with the jumper wire and connect a spark plug directly to the coil wire (the one that normally goes to the distributor). Make sure that the spark plug is touching a good ground on the engine block and is positioned where you can see it clearly. Then put power to the coil positive terminal, connect the negative terminal to ground, and when you remove the ground jumper wire you should get a spark at the plug. If not, the coil is bad.
Joe

 

[Anonymous]

Ok, I just redid that test with the spark plug in the coil wire touching the block. There was a tiny spark at the spark plug (I assumed the spark would be a lot bigger than that), so I guess that means the coil is good. I'm sorry for the misunderstanding; when it comes to electrics I really am pretty lost, although I've gained a lot more knowledge over the past couple of days with the forum's help. So, I guess I've now got to get a new starter and try again. Would you guys recommend just going to the Duraspark ignition instead of messing with the points? Thanks again for the help.

Mike