CRG Discussion Forum

Camaro Research Group Discussion => Maintenance => Topic started by: ZLP955 on May 01, 2018, 07:46:53 AM

Title: Ignition Coil Bench Test
Post by: ZLP955 on May 01, 2018, 07:46:53 AM

What's the correct procedure for bech-testing a stock points ignition coil, and what are the minimum readings for primary and secondary windings to confirm if coil is good or bad?
This is for my Delco-Remy 298 B-R, by the way.

Title: Re: Ignition Coil Bench Test
Post by: ZLP955 on May 03, 2018, 09:56:07 AM

OK, so after some research on this, I found the following specifications from the 1969 Chassis Service Manual for V8 Engine, non-transistor ignition:
Coil Primary Resistance: 1.77 to 2.05 ohms
Coil Secondary Resistance: 3,000 to 20,000 ohms

Primary resistance measured with multimeter between the coil +ve and -ve terminals.
Secondary resistance measured with multimeter between the high tension tower and either +ve or -ve terminal.
Secondary resistance range seems fairly broad, for example a reading of 3k ohms is within spec but would give a significantly different spark quality than a coil reading at the upper limit of 20k ohms.....

Anyway, thought I'd close out the question for future searches, time to check my coil now.

Title: Re: Ignition Coil Bench Test
Post by: ZLP955 on May 05, 2018, 05:29:31 AM

Got 2 ohms on the primary and 12,000 ohms on the secondary winding, so looks ok.

Title: Re: Ignition Coil Bench Test
Post by: ko-lek-tor on May 05, 2018, 11:06:39 AM

I , for one, appreciate this diagnostic information.

Title: Re: Ignition Coil Bench Test
Post by: bcmiller on May 05, 2018, 02:06:26 PM

Thanks Tim.

Title: Re: Ignition Coil Bench Test
Post by: HOT3O2 on May 05, 2018, 02:53:30 PM

Thanks Tim, I just picked up a coil for my car and now I can check it out. We all appreciate the info.

Title: Re: Ignition Coil Bench Test
Post by: ZLP955 on May 05, 2018, 09:40:35 PM

No worries, needed to increase my diagnostic knowledge and hope this helps someone else.

Title: Re: Ignition Coil Bench Test
Post by: Sauron327 on May 09, 2018, 04:44:32 PM

Coil testing info here: http://www.camaros.net/forums/18-engine/452690-starts-then-stops.html

Title: Re: Ignition Coil Bench Test
Post by: ZLP955 on May 10, 2018, 12:59:27 PM

Scott what does a parts store hot-run test involve, and does it factor in the factory coil specs?

Title: Re: Ignition Coil Bench Test
Post by: Sauron327 on May 11, 2018, 12:47:17 AM

Just put the info out there. Ask a specialist in that business who knows the details.

Title: Re: Ignition Coil Bench Test
Post by: 70z28lt1 on May 12, 2018, 08:43:25 PM

Hmmmm.....got 2.2 ohms primary and 12.3K ohms secondary on an original 270 B-R.  The primary is just a squeak over.  Good?

Title: Re: Ignition Coil Bench Test
Post by: ZLP955 on May 12, 2018, 11:22:50 PM

No expert but would think that'd be fine, from my research the resistance of the secondary winding is more important to getting a consistent good spark at the high-tension post. Another thing to watch is some digital multimeters have a base resistance (either internally or on the test leads) that needs to be deducted from the readout when on the coil terminals - if you touch the red and black probes together and get anything over 0.0 on the display, subtract that from the readings at the coil terminals. Also make sure there is good contact to the coil terminals, any traces of oil or even light corrosion can affect the accuracy of the readings.