How to check an ignition coil is working properly/in spec

MmSadda · 05-08-2011, 06:58 PM

I've had some issues with my car starting and whatnot as of late, and I believe my coils may be out of spec. What's the easiest way to test and make sure they're working properly? I've got a digital multimeter to work with (of course)

Any help is appreciated!

Thanks

Collin

My5ABaby · 05-09-2011, 07:35 AM

There's a test procedure in the FSM that involves resistance. That's the only one I personally know about.

MmSadda · 05-09-2011, 12:56 PM

Cool! Ill check out the fsm as soon as I get a chance. Thanks!

Ptotherice · 06-01-2011, 09:34 PM

One easy way to do it, unplug it, put a bolt where the spark plug goes (make sure it touches the metal in the plug wire, and then hold it near the body of the car. Now make sure you have PLENTY of insulation between your hand and the coil (like a plastic something to hold it far away from your hand). Turn off any of the fuel (pull fuses) and crank the engine over (it won't start) and look for a strong, loud, thick spark with a decently long jump. Don't hold it too close. That sounds harder than it really is, takes all of 2 or 3 minutes.... might try the fsm if it's easy.

88turboii · 06-02-2011, 11:44 AM

an easy way is turn the engine over while holding the spark plug connector slightly off the post and see if spark arcs. you could also simulate engine turning over by taking out the CAS and spin it by hand with the key in "run" position

to benchtest it, just find the pinout and use 12V on one pin, and briefly ground the other and you should see spark arc

Max777 · 06-02-2011, 01:26 PM

guys, the bolth thing sounds stupid, a proper spark tester that will simulate running condition spark resistance only costs a few bux, and will give you the best result.

problem with testing spark the ghetto way: it takes 5K ohms of resistance for the spark to jump in open air, it takes 30,000 ohms of resistance for it to jump under compression in the cylinder

t_g_farrell · 06-02-2011, 02:14 PM

Coils are speced in the FSM usually for secondary and primary resistance. Just
use your DVM to measure them and see if they are in spec on all of the posts.

When I went hunting for some TFI coils, I brought my DVM with me to the JY
and did this as I was finding coils. Saved me a lot of trouble because the dead
ones were easy to see based on the resistance.

05-08-2011, 06:58 PM	#1
MmSadda BOOSTED COLON Join Date: Feb 2008 iTrader: (0) Posts: 88 Rep Power: 17	How to check an ignition coil is working properly/in spec I've had some issues with my car starting and whatnot as of late, and I believe my coils may be out of spec. What's the easiest way to test and make sure they're working properly? I've got a digital multimeter to work with (of course) Any help is appreciated! Thanks Collin

05-09-2011, 07:35 AM	#2
My5ABaby Sigh..... Join Date: Feb 2008 Location: Murfreesboro, TN iTrader: (6) Posts: 2,377 Rep Power: 19	There's a test procedure in the FSM that involves resistance. That's the only one I personally know about. __________________ 1986 Sport: 132k miles, 5A (Sapphire Blue Metallic), Tokico Blues, Racing Beat Springs, Custom LED tailights (only S4 LED tails in the world), SSR Mark II, Racing Beat exhaust, S5 black interior, Rotary Resurrection rebuild at 120k miles Community Service Manual RotorWiki "Imagination costs nothing; we could build square locomotives or fly to Mars" - Felix Wankel Yesterday is history, tomorrow is a mystery, but today is a gift. That is why it is called the "present."

06-02-2011, 11:44 AM	#5
88turboii destroy, rebuild, repeat Join Date: Feb 2008 Location: Charleston, SC iTrader: (0) Posts: 395 Rep Power: 17	an easy way is turn the engine over while holding the spark plug connector slightly off the post and see if spark arcs. you could also simulate engine turning over by taking out the CAS and spin it by hand with the key in "run" position to benchtest it, just find the pinout and use 12V on one pin, and briefly ground the other and you should see spark arc __________________ 1993 RX-7 Touring MB, stockport 13B-REW, 9.4CR rotors, T04S 60-1/p-trim single turbo 1986 RX-7 Base project track beast Last edited by 88turboii; 06-02-2011 at 11:47 AM..

06-02-2011, 01:26 PM	#6
Max777 Pirate Join Date: Mar 2008 Location: Central IL iTrader: (5) Posts: 1,323 Rep Power: 18	guys, the bolth thing sounds stupid, a proper spark tester that will simulate running condition spark resistance only costs a few bux, and will give you the best result. problem with testing spark the ghetto way: it takes 5K ohms of resistance for the spark to jump in open air, it takes 30,000 ohms of resistance for it to jump under compression in the cylinder __________________ Rotaries:They are NOT that complicated!

06-02-2011, 02:14 PM	#7
t_g_farrell Waffles - hmmm good Join Date: Aug 2008 Location: Huntersville, NC iTrader: (0) Posts: 757 Rep Power: 0	Coils are speced in the FSM usually for secondary and primary resistance. Just use your DVM to measure them and see if they are in spec on all of the posts. When I went hunting for some TFI coils, I brought my DVM with me to the JY and did this as I was finding coils. Saved me a lot of trouble because the dead ones were easy to see based on the resistance. __________________ 1980 GS stockport, Fat Nikki, RB Dual Facetfuel pumps, Holley regulator, RB Street port exhaust, 2GDFIS, MR2 MK I electric fans, 2G strut bar, relayed fans, lights and fuel pump, LEDs Project Fat Nikki Budget 12A rebuild Video setup < $30.00

05-09-2011, 12:56 PM	#3
MmSadda BOOSTED COLON Join Date: Feb 2008 iTrader: (0) Posts: 88 Rep Power: 17	Cool! Ill check out the fsm as soon as I get a chance. Thanks!

06-01-2011, 09:34 PM	#4
Ptotherice Rotary Fan in Training Join Date: Aug 2010 iTrader: (0) Posts: 39 Rep Power: 0	One easy way to do it, unplug it, put a bolt where the spark plug goes (make sure it touches the metal in the plug wire, and then hold it near the body of the car. Now make sure you have PLENTY of insulation between your hand and the coil (like a plastic something to hold it far away from your hand). Turn off any of the fuel (pull fuses) and crank the engine over (it won't start) and look for a strong, loud, thick spark with a decently long jump. Don't hold it too close. That sounds harder than it really is, takes all of 2 or 3 minutes.... might try the fsm if it's easy.

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