Ignition coil check on my 76 (1 Viewer)

Joined
Mar 18, 2021
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Temecula CA
Hi everyone! Here are my ohm readings from the ignition coil. Is it ok or replace?
Primary 3.1
Secondary 9.93

Its original...
20200808_120526.jpg
 

1911

chupacabra
Joined
Aug 11, 2006
Messages
6,474
Location
Parker County, Texas
Hi everyone! Here are my ohm readings from the ignition coil. Is it ok or replace?
Primary 3.1
Secondary 9.93

Its original...View attachment 2632214

Per the factory service manual, the late coil (used with an igniter) primary coil resistance should be 0.5 - 0.7 Ohms, and the secondary coil resistance should be 11.5 - 15.5 kOhms.

Are you sure you were reading the right band on your ohmmeter?
 
Joined
Mar 18, 2021
Messages
19
Location
Temecula CA
Per the factory service manual, the late coil (used with an igniter) primary coil resistance should be 0.5 - 0.7 Ohms, and the secondary coil resistance should be 11.5 - 15.5 kOhms.

Are you sure you were reading the right band on your ohmmeter?
Oh I'm sure I'm doing it wrong. 😆 I just rechecked and took some
20210331_195623.jpg
20210331_195729.jpg
pictures with my settings.
 

1911

chupacabra
Joined
Aug 11, 2006
Messages
6,474
Location
Parker County, Texas
Oh I'm sure I'm doing it wrong. 😆 I just rechecked and took some View attachment 2632369View attachment 2632370pictures with my settings.

Well, your secondary resistance is 10,180 Ohms, so much closer to spec but not quite there. Your primary resistance is still an order of magnitude more than spec, unless I'm not reading the scale on your meter correctly.

The ignition coils that I've seen go bad, usually cracked/broke some of the wire windings due to vibration. Usually when that happens, the resistance numbers are way off, especially in the secondary circuit. So I'm not sure what to think about yours. Has your truck been running with this coil? Did you have any symptoms that made you suspect a bad coil? Bottom line: that one is out of spec, and a new one should not be expensive, so if it was mine I would replace it.
 

FJ40Jim

The Cruiser Whisperer
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The pictured FSM is for the fully electronic ignition and no ballast resistors.

The OPs truck has points and 2 ballast resistors. Quite a different animal.
 
Joined
Mar 18, 2021
Messages
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Location
Temecula CA
Thanks for the replies. I recently rebuilt the engine and carb. I have the truck running decent(starts and runs good, no loud backfires, chugging). She's runs alittle rich with an occasional pop out the tail pipe and notice the timing bb jumps around at times. I'm sure carb needs better tuning. I only checked the coil mainly because I was curious on its readings.
 

FJ40Jim

The Cruiser Whisperer
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If it is starting & running, the coil is probably okey-dokey. If the coil is damaged/dented or is leaking oil out the top crimp, then it needs replaced.
 

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