another no spark chinese quad
#12
02-15-2012, 02:20 AM
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Attach a "separate battery to your coil" ? And you expect a spark?
This is dangerous advice. Don't do it. It won't work, and you could start a fire.
Jesse: You can't have tried this... Where are you coming from offering advice like this?
This is dangerous advice. Don't do it. It won't work, and you could start a fire.
Jesse: You can't have tried this... Where are you coming from offering advice like this?
Hello,
Spark or ignition problems:
Everything may be okay, but you may not have spark when the plug is in.
Under demand the spark can be extinguished and not spark.
Check your spark plug wire first. It should read about 7k ohms per foot though any automotive book will tell you.
You may have a faulty ignition module, but let’s check the coil first.
Coil:
Try taking a voltage reading at the positive pole of the coil (+) when you’re cranking. It should be at least 7-8 volts though some vehicles may require higher. Set your multimeter to the voltage range that contains 12 volts. If it's an analog meter (Dial or needle type). If it's digital you don't have to. Put it on the DC voltage setting. If the voltage is low then most likely that's your problem.
Check the wires on the coil to see if they're loose or broken. An easy way of finding if your coil is faulty is to attach a SEPARATE battery to your coil. Attach the ground off your remote battery's ground by a small cable or wire to a GOOD ground point on you FRAME, or a fork, or brake pedal or whatever, nothing painted. There are 2 poles, or terminals, on your coil that your wires connect to. Attach the Positive side of the REMOTE battery to the POSITIVE side, or terminal, of the COIL. It should have a + sign or +mark next to where the wire connects. The other wire, terminal should be -, but don't concern yourself with that. If your engine starts then you have no voltage to your coil and your coil is good. If it doesn't start then you have a faulty coil, poor connection, or a faulty ignition module. The easiest way to find out if your coil is bad is to substitute another. If it starts then that’s your problem, the same with your ignition module. . If you want to learn and save yourself some money sometimes it’s better to borrow and try than to just buy and hope for the best.
How to Check an Ignition Coil:
Measure the coil primary resistance. Using an ohmmeter, connect the red lead to the coil's positive (+) electrical connector, and the ohmmeter's black lead to the coil's negative (-) electrical connector. An average resistance reading could be between 0.3 and 1.0 ohms.
Measure the coil secondary resistance. Connect the ohmmeter's black lead to the coil's negative (-) electrical connector and the ohmmeter's red lead to the coils terminal-where the distributor or spark plug wire attaches to. A typical resistance reading could be 8,000 to 11,500 ohms.
Replace the coil if any of the readings for your particular coil is bellow or above the specifications indicated in your service manual.
Reinstall the coil, electrical connector, wires and connect the negative cable to the battery terminal. If everything checks out okay then your timing may be off.
Good luck.
Spark or ignition problems:
Everything may be okay, but you may not have spark when the plug is in.
Under demand the spark can be extinguished and not spark.
Check your spark plug wire first. It should read about 7k ohms per foot though any automotive book will tell you.
You may have a faulty ignition module, but let’s check the coil first.
Coil:
Try taking a voltage reading at the positive pole of the coil (+) when you’re cranking. It should be at least 7-8 volts though some vehicles may require higher. Set your multimeter to the voltage range that contains 12 volts. If it's an analog meter (Dial or needle type). If it's digital you don't have to. Put it on the DC voltage setting. If the voltage is low then most likely that's your problem.
Check the wires on the coil to see if they're loose or broken. An easy way of finding if your coil is faulty is to attach a SEPARATE battery to your coil. Attach the ground off your remote battery's ground by a small cable or wire to a GOOD ground point on you FRAME, or a fork, or brake pedal or whatever, nothing painted. There are 2 poles, or terminals, on your coil that your wires connect to. Attach the Positive side of the REMOTE battery to the POSITIVE side, or terminal, of the COIL. It should have a + sign or +mark next to where the wire connects. The other wire, terminal should be -, but don't concern yourself with that. If your engine starts then you have no voltage to your coil and your coil is good. If it doesn't start then you have a faulty coil, poor connection, or a faulty ignition module. The easiest way to find out if your coil is bad is to substitute another. If it starts then that’s your problem, the same with your ignition module. . If you want to learn and save yourself some money sometimes it’s better to borrow and try than to just buy and hope for the best.
How to Check an Ignition Coil:
Measure the coil primary resistance. Using an ohmmeter, connect the red lead to the coil's positive (+) electrical connector, and the ohmmeter's black lead to the coil's negative (-) electrical connector. An average resistance reading could be between 0.3 and 1.0 ohms.
Measure the coil secondary resistance. Connect the ohmmeter's black lead to the coil's negative (-) electrical connector and the ohmmeter's red lead to the coils terminal-where the distributor or spark plug wire attaches to. A typical resistance reading could be 8,000 to 11,500 ohms.
Replace the coil if any of the readings for your particular coil is bellow or above the specifications indicated in your service manual.
Reinstall the coil, electrical connector, wires and connect the negative cable to the battery terminal. If everything checks out okay then your timing may be off.
Good luck.
#13
02-15-2012, 10:28 AM
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What you would see is very narrow high frequency (and moderately high voltage) AC pulses. The ignition coil primary is just a couple hundred turns of wire wound around an iron core. Its DC resistance is very low, but its impedance is much higher for high frequency AC voltages because the ignition coil primary winding is inductive.
The entire ignition coil is just a step up transformer with a turns ratio of about 100:1. Thus those hundred volt spikes on the input get stepped up to 10,000 volts or more at the spark plug. But notice that the frequencies here are really high. The ringing waveform detail shows a main frequency content of about 30 KHz.
Current in amps = 12.6 volts divided by 0.3 ohms
That's 42 amps!!! (The above formula is Ohm's law BTW).
To calculate how much power will be dissipated by that tiny little ignition coil:
Power in watts = voltage (in volts) times the current (in amps)
That would be 529 watts!!!
When you hook up an external battery it is not likely to have a fuse in line, so there is no protection at all from such massive current flow. This is why I raised the possibility of fire.
I hear this claim about 12 volts on the ignition coil primary a lot, and I often wonder where it comes from. The only thing I can think of is the old Kettering style ignition system on cars from the early 1970's and before. In this system 12 volts was applied to one side of the ignition coil primary and the other side was grounded through a cam driven set of 'points' (basically a switch) in the distributor. The points only briefly applied 12 volts to the ignition coil and then opened back up. A condenser (i.e. a capacitor) across the points then formed a series resonant circuit with the inductance of the coil primary which would then ring at 30 KHz or so. Even though 12 volts was applied to the coil primary it was being switched on and off so rapidly that you could consider this to be an AC waveform, and the inductance of the primary limited the current.
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