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Topic: Check Your Ign. Coils! (Read 2015 times) previous topic - next topic

Check Your Ign. Coils!

The Red-Winged Blackbird started missing/sputtering recently, so I went through the whole ignition system to find out what the problem was.  When I tested the resistance in the primary circuit of its coil, I read 1.2 ohms.  To be within specifications, the primary circuit should have between .3 and 1 ohm of resistance.  It looks like I found the cause of the missing.

For the hell of it, I went over to my Sport and checked its coil too.  It too tested bad with too much resistance.  It looks like I'm gonna be buying 2 coils.

This experience left me wondering how many other guys on this forum have original equipment coils on their cars that are bad, or on the verge of being bad.  Checking the resistance in the primary and secondary circuits of your coil is easy to do.  Coils are cheap too.  Why not check your coils out? 

To check your coil's primary circuit, use a multimeter to check the resistance between the 2 small, flat terminals on your coil.  If resistance is between .3 and 1 ohm, it's good.  Anything even slightly outside that range and you need to replace it, because it's bad. 

To check your coil's secondary circuit, check the resistance between the negative terminal of your coil and the output terminal that goes to your distributor cap.  To be within spec, resistance should be between 8k and 11.5k ohms.
William

Check Your Ign. Coils!

Reply #1 –
My old 86, the coil was actually broken and cracked. When I pulled it off. Haven't needed to replace another one yet, but wouldn't be a bad idea.
Quote from: jcassity
I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
Hooligans! 
1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
1986 cougar.
lilsammywasapunkrocker@yahoo.com

Check Your Ign. Coils!

Reply #2 –
Good info.............can we sticky this stuff??  Or maybe it's there and I just don't see it.
1988 T-Bird Sport Coupe--5.0 HO, MAF swap, 1-5/8" shorties, BBK/Flowmaster exhaust, Explorer intake, 70mm Edelbrock TB, T5, B&M short throw, Centerforce clutch and PP, disc brake TC rear w/ 3.55's, TC front brakes, '98 Cobra springs, DIY SFC's, other misc .  14.05 @ 98mph with launching too low and shifting too high.

Check Your Ign. Coils!

Reply #3 –
I don't think you'll find that info here in a sticky, but I agree that it would be a good idea to make it a sticky.  How many times have you read a thread started by someone with a Fox chassis car that had an unexplained miss they couldn't figure out?  Yea.  It happens all the time.  Sure; a lot of these misfiring issues are caused by bad ign. Modules, but a lot of cars out there have bad coils that are causing engines to miss.
William

Check Your Ign. Coils!

Reply #4 –
definitely sticky status.. i keep overlooking and forgetting to check the coil in the white pos.. runs better with the new TFI, but still idles like a daewoo
ShadowMSC.com < < Still Under Construction

R.I.P. 'Zump' 8/29/86 - 11/11/11
3- 87 TC's / 1 really mean 83 Capri RS / 94 Sonoma SAS Project on 37x12.50 TSL Radials / 88 S10 that's LITERALLY cut to pieces / 84 F150 SAS, 351M, 39.5 TSL's / 85 Toyota regular cab, 22R 5spd, 3/4" drop, my little junkyard save/daily driver

Check Your Ign. Coils!

Reply #5 –
I had a MSD blaster on the 86 at one point. Was working under the hood at night, the entire coil was surrounded by a blue arc :giggle:

Check Your Ign. Coils!

Reply #6 –
LOL
click on my diy link,, its all in there plus a whole lot more.

your meter your using first off needs defined.

if your using a digi meter, turn it on and adjust the range to its lowest amount.
touch you meter leads together while on ohms scale and remember the number you see.

take the resistance check of the thing your working
subtract the "out of calibration" amount from you reading.

with an buttstuffog meter, this isnt such a problem.

Check Your Ign. Coils!

Reply #7 –
Ok guys this made me think and I decided to ohm mine. Primary coil check out just fine in spec, checked the secondary and Im only getting about 3200 ohms. Now this is a MSD Blaster coil to, just so you know. I have only issue when Im at full boost, kinda like its running out of steam.

Check Your Ign. Coils!

Reply #8 –
What plug gap are you running?  Too wide of a gap could cause that problem due to increased cylinder pressure.
William

Check Your Ign. Coils!

Reply #9 –
Im at a gap recommended by some guys over on turboford, 28. Ive been thru fuel, boost leaks, and for the most part a full tune-up. I read this and checked mine since it got me to thinking about it.

Check Your Ign. Coils!

Reply #10 –
Your gap sounds good.  You DO have a spark box, don't you?
William

Check Your Ign. Coils!

Reply #11 –
If your talking about a MSD ignition, then no. This coil is one of them that was marketed as a better replacement than stock. Uses the stock harness setup and all.

Check Your Ign. Coils!

Reply #12 –
I wouldn't be surprized if that's your problem right there.  You just might need a spark box to fire your plugs correctly under high boost.  MSD Blaster coils aren't much better than a stock Motorcraft coil would be at firing your plugs under high boost conditions.
William
 

Check Your Ign. Coils!

Reply #13 –
Well I did a little searching on MSD's site and looked up specifically the coil I have. Im testing 1300 ohms less than they say spec is, that may be a issue.