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Testing Ignition Coil


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9 replies to this topic

#1 rdweninger

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Posted 16 January 2013 - 05:08 PM

Hello All,
I have what I believe is an ignition problem.
There seems to be varying thoughts on testing coils in my search results. I have 2 questions for an 1983 EA81.
1. When testing the secondary winding... one probe from the ohms meter goes to the center of coil... where does the other probe go? Positive or Negative side of coil?
2. What are the actual specification ranges for primary and secondary resistance?

If the coil checks out, I will swap distributors. But, have to make a trip to Auburn, WA to get my spare.
Thanks in advance, Subie Bros.

#2 nipper

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Posted 16 January 2013 - 05:22 PM

Can you describe the problem first?

Coils can be a bit difficult to diagnose directly so you tend to rule everything else out first since the failure can be temp or related to direction.

#3 rdweninger

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Posted 16 January 2013 - 08:05 PM

the problem seems to be random spark failure. The car 'hiccups' on acceleration. The tach is jumping around between 2-3500 rpm. It seems very similar to my EA82 which was fixed with a rebuilt distributor.
However, I don't have a spare disty to swap... am looking for one. So I thought I would at least rule out the coil. Just need some reliable specs on the coil.

#4 nipper

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Posted 16 January 2013 - 08:10 PM

Does it happen hot cold or whenever. This does sound a bit more disty then coily.

Old coils usually get buggy when they heat up or if mounted sideways on turns.

#5 rdweninger

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Posted 17 January 2013 - 04:06 PM

I just bought the car a week ago. The PO reported that the car was 'jumpy'. so this has been a sympton for a while. It is the same whether cold or warmed up. The carb is filthy. I'll have some time this weekend to work on it. So anyone with the coil resistance specifications? And testing the secondary windings procedure? Thanks to all.

#6 TomRhere

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Posted 18 January 2013 - 04:14 AM

Nippondenso coil;
primary = 1.13-1.35, secondary = 10,795-14,605

Hitachi coil;
primary = 1.04-1.27, secondary = 7,360-11,040
according to the FSM.

Check the coil primary windings with the meter leads on the + and - terminals.
Secondary windings are from the + to the center terminals.

Pull the disty cap and check for any side-to-side movement of the shaft. Worn bushings can cause run rough, and a jumpy tach is one indicator of that.
Bad pick-up or faulty wiring for it could be issue.

I had one Hitachi disty that the magnet under the "C" shaped piece shattered, causing it to run rough, die and not restart.
Magnet part numbers
491988711 for '84+,
491987401 for '83-.

Edited by TomRhere, 18 January 2013 - 04:18 AM.


#7 ivans imports

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Posted 18 January 2013 - 11:57 AM

distributor module or cracked magnet but diss problem for shure

#8 rdweninger

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Posted 18 January 2013 - 01:44 PM

Thank you TomRhere !!! You da man.
I checked the shaft play... didn't feel any movement. However, there was alot of red 'dust' in the cap. I'm assuming that is ferrous material.
I had my ea82 disty rebuilt about a year ago... cost $140. Do you think that's reasonable or should I just do it myself? I've seen the distributor test machine... looks complicated.:-\ Thank you for your help. I appreciate it.

#9 naru

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Posted 18 January 2013 - 02:17 PM

Red dust means the spark is grounding out inside the disty.
The dust is oxidized iron from the shaft/advance weights.
If you look carefully,you will see small eroded areas.

I would check plug wires,plug gaps,rotor and cap.
Doublecheck the shaft play too.

I see this most often on GM HEIs where the spark fires straight thru the rotor plastic.

Edited by naru, 19 January 2013 - 03:07 AM.


#10 ajp

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Posted 18 January 2013 - 06:32 PM

sounds like a distributor problem. you can get a new cap, spinner, wires and plugs for under $50. I had the same problem once, car was buckin on me now and then, eventually kept doing it all the time.
super easy to do yourself. hardest part is getting the plugs in and out. when you put the new wires on, do them one at a time, and make sure you get them in the right place and order. napa wire set worked ok for 84 GL. not a spare inch on them though.




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