testing an ignition coil

grumpyvette

grumpyvette

Administrator
Staff member
"A SIMPLE QUICK CHECK FOR YOUR COIL IS
:CHECK YOUVE GOT 12 VOLTS, AT THE COIL, PUT A TEST LIGHT TO GROUND AND THE NEG SIDE OF COIL AND CRANK ENGINE THE TEST LIGHT SHOULD FLASH OR FLICKER.(ANALOG METERS WITH A SWINGING NEEDLE,SWEEP ARE BETTER THAN DIGITAL)
THIS WILL TELL IF YOUR TRIGGER IS WORKING.
NEXT TAKE A SPARK PLUG AND HOOK IT TO YOUR COIL WIRE AND GROUND THE PLUG,BODY AND CHECK FOR SPARK THERE ACCROSS THE PLUG GAP,WHEN YOU CRANK THE CARS ENGINE, BE AWARE MANY IGNITIONS WON,T HAVE VOLTAGE UNTILL YOU HAVE 4-5 PSI OF OIL PRESSURE, GAP THE TEST SPARK PLUG AT .150, SPARK SHOULD BE BRIGHT BLUE,IF ITS YELLOW OR RED, CHECK ENGINE GROUNDS FIRST, THEN START LOOKING FOR OTHER PROBLEMS, CHECK BETWEEN THE TWO SMALL TERMINALS YOU SHOULD SEE A FEW OHMS RESISTANCE, CHECK BETWEEN EACH OF THE SMALL SIDE TERMINALS TO THE COIL WIRE YOU SHOULD SEE SEVERAL THOUSANDS OF OHMS RESISTANCE minimum
YES IN SOME CASES THE ENGINE WILL STILL RUN, BUT RUN POORLY WITH THE COIL POLARITY REVERSED
ignition spark should be bright blue and impressive, if its, weak,narrow, yellow or red theres a problem so research the cause, verify the coil and voltage
igwirecrimp.jpg

http://auto.howstuffworks.com/ignition-system3.htm
d4d8.gif


http://www.corvettefever.com/techarticl ... index.html

http://www.kronjaeger.com/hv/hv/src/ign/index.html

http://www.corvettefever.com/techarticl ... index.html

http://cranecams.com/pdf/90001700c.pdf

http://www.autozone.com/autozone/repair ... title=test

http://autorepair.about.com/od/troubles ... st-ohm.htm

http://www.ehow.com/how_4558863_check-i ... -coil.html

http://www.youtube.com/watch?v=eKWsI2vNxPs



viewtopic.php?f=48&t=2828&p=7301&hilit=+coil+testing#p7301

http://www.ladyada.net/learn/multimeter/

http://autorepair.about.com/cs/troubleshooting/l/aa062902b.htm

http://autorepair.about.com/od/troubleshooting/ss/coil-test-ohm.htm

http://arrc.epnet.com/autoapp/9110/9110 ... System.htm

http://www.corvetteflorida.com/forums/s ... php?t=5717

http://www.ehow.com/how_2321232_test-ignition-coil-car.html


and yes THE BETTER multi spark control boxes are well worth the expence as they tend to stop or make plug fouling significantly lower

http://www.msdignition.com/page.aspx?id=4209

http://www.msdignition.com/page.aspx?id=3206

http://www.msdignition.com/page.aspx?id=9765

by plug body do you mean ground the threads to something? Or just hold the electrode up against the block?

I generally hold the main plug body near the hex section firmly against the block

just for clarification, you should see a few ohms of resistance between the the two small terminals (primary coil resistance) and several thousand ohms resistance between either small terminal and the center terminal leading to the distributor cap (secondary coild resistance), correct?


yes, generally under 5 ohms between the small terminals, and over 30,000 ohms between the small and the distrib wire plug on the coil



Connect the red test lead of a digital ohmmeter to the primary side of the coil and the black test lead of the ohmmeter to the secondary side of the coil. The displayed reading on the ohmmeter should be between 0.7 and 1.7 ohms. You may have a faulty ignition coil if the readings displayed on your ohmmeter are not within this range.
4

Connect the red test lead of the ohmmeter to the coil's high-tension terminal and connect the black test lead to the coil's negative connection. The reading displayed on the ohmmeter should fall between 7,500 and 10,500 ohms. Your coil may be failing if the reading is not within this range.

Read more: How to Diagnose a Faulty Ignition Coil | eHow.com http://www.ehow.com/how_5982869_diagnos ... z21gN3XOmC
 
getting no spark, or its running badly on one or two cylinders?

first
check the most obvious, carefully verify that two of the plug wires in the firing order are not out of sequence.
next
verify your getting spark at the plug by starting the engine with the suspect plug wire connected to a Phillips screw driver rather than the spark-plug, and remember to only hold the plastic, but allow the steel part of the screw driver to be about 1/16" from the engine so it can potentially arc to the block verifying your getting spark. the spark should be BLUE not red or yellow in appearance.if the sparks yellow or red verify the coil polarity's correct and the voltages is at about 13-13.8 volts (same as the battery) and check the engine ground is good.
next
if your getting spark from that screw driver test,replace that spark plug, if your not, test the plug wire with an ohms meter it should read UNDER 400-500 ohms per foot of length.in most cases but,(compare its resistance to several other wires on your engine, if its markedly different theres a big problem and ID replace all the plug wires)
next
Replace the cap and rotor if they are suspect, their cheap and if they have over 65-80k your probably going to need one anyway soon.
 
tracking down a MISS/STUMBLE, or other problem?







http://www.clarks-garage.com/shop-manua ... tm#oil-low

http://www.procarcare.com/includes/cont ... fPbs1.html

GOOD COILS TESTED WITH AN MULTI METER SET TO OHMS
normally read ,
between 0.8 ohms-to-1.3 ohms between the positive and neg electrical connections
10,000-13,000 ohms between either of the electrical connections and the coil to distributor wire connection terminal
and off the chart between the positive and neg electrical connections and the outer case ground.
if your experiencing an ignition problem .drop back to the basics and test your battery voltage, alternator out-put, all battery connections, frame grounds, and all ignition components like ignition wire resistance in OHMS and coils, rotors , caps and firing order,distributor end play and bearings,advance weights and springs,etc. you would be amazed at how often minor parts cause major issues

image_6238.jpg

http://www.harborfreight.com/5-in-1-dig ... 98674.html
viewtopic.php?f=50&t=609&p=810&hilit=multi+meter#p810

coil1.jpg

coil2.jpg




more info


http://www.justanswer.com/uploads/carhe ... nition.pdf

http://autorepair.about.com/library/images/bl293lib.htm

Testing article on coils:

http://autorepair.about.com/cs/troubles ... 62902b.htm
 
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some ignitions and some coils require a resistor in the ignitions voltage supply circuit to drop the input voltage (THATS the white rectangle on the firewall!!) in most cases the instructions with the ignition will point this out, READ THE DIRRECTIONS YOULL BE SURPRISED AT WHAT YOU MIGHT FIND OUT!!


as ALWAYS its the links and sub links that contain a great deal of info you'll need

www.hagerty.com

Ignition Coil Basics - Hagerty Media

Even for the somewhat knowledgeable among us, the ignition system occupies an almost magical place in our automotive understanding. A place occupied by the intricacies of the Quasi-turbine engine and the Pogue Carburetor. We understand the principles, but whatever actually happens “in there” is...
www.hagerty.com www.hagerty.com

mechanics.stackexchange.com

What is the expected voltage of a coil to a distributor supposed to be?

According to, https://www.carparts.com/classroom/ignition.htm . I have two wires that go to positive side of coil, one from resistor / ballast and the other from ignition switch, is this correct? My
mechanics.stackexchange.com mechanics.stackexchange.com


What type of coil can I use with the Ignitorâ„¢? How do I check my coils resistance? (12V negative ground only)
To determine if your systems coil is compatible with the Ignitor, some measurements should be taken prior to installation of the Ignitor. Caution… While performing this test, never leave the ignition switch on for more than 30 seconds at a time.

Set your voltmeter to a 15 or 20-volt scale. Attach an 18 or 20 AWG jumper wire from the negative coil terminal to an engine ground. Attach positive (red) lead of your voltmeter to the positive side of the coil, and the negative (black) lead to an engine ground. Turn the ignition switch to the run position. Now read the voltage at the positive coil terminal. Turn the ignition switch off. If the voltage measured is approximately 12 volts, no resistance wire is present. A typical resistance wire will provide 9 - 6 volts.

The next step is to determine the resistance in the primary ignition. Label the wires attached to the coil terminals and note their appropriate location. Make sure that the ignition switch is off and disconnect all wires from the coil. Adjust your meter to the lowest ohm scale. If you are using an analog style meter make sure to zero the needle.

Measure from the negative terminal to the positive terminal. Write your measurement down.

Now the maximum system amperage can be determined, divide your voltage measurement by your coil resistance measurement. This will give you the system current or amperage.

Four and six cylinder engines should not exceed 4 amps. Eight cylinder engines should not exceed 8 amps. If the total amperage in your system is higher than the amount recommended for your application, you should install a ballast resistor.

Example
Voltage 12
Resistance 1.5
12 / 1.5 = 8
 
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BTW THERES TWO VERSIONS ON ACCEL COILS
there are 2 versions, a 1.5 ohm version and a 3 ohm version, and a 3 ohm should be able to handle it without re-installing the ballast resistor.
 
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