Original ignition coil: Testing? Replacement?

[KevAndAndi]

I am waiting on a new voltage regulator for my alternator, so I decided to take this opportunity to remove the (original) ignition coil and inspect the connections. The connections on the two posts were predictably corroded. One quick-disconnect was alarmingly loose. I'm thinking of replacing these connectors with eyelet connectors, which is what I did on my fuel pump. I don't really feel the need to be able to disconnect things quickly.

While I like originality, I also favor reliability - so how concerned should I be about the 35-year-old coil? How robust is a coil? What are signs that a coil might be reaching the end of its life? How does one test a coil?

[spider2081]

This might not be text book or the specs given in a Spider manual:
The coil is a step up transformer with a single winding that is tapped into. They are called autotransformers in other applications. A sort of go-no-go test is made with an Ohm Meter. The resistance between the 2 small posts is usually less that 5 ohms. I think the stock Fiat coil is about 3 ohms. Be sure to put you meter leads together and see if your meter indicates zero when making this test. If it is a digital meter and indicates something like 0.7 that is the resistance of the leads and you would subtract that from your measurement. The resistance between the distributor contact on the coil and either of the other coil posts should be somewhere around 8000 to 10,000 ohms.
I agree with installing ring terminals. I have done this with all the grounds also. Prior to this year I worked in Aviation and purchased all my crimp terminals from the shop supply house. I recently purchased some crimp terminal on-line and was surprised that the material they were made of was far inferior. I could not make a crimp that I could not pull apart with my hands. The metal for the crimp ares was too thin to maintain the required force on the wire after crimping. I would suggest making a test crimp on a wire off the car to be sure you have good terminals. A good crimp can not be pulled of the wire after its crimped.

[KevAndAndi]

This might not be text book or the specs given in a Spider manual:
The coil is a step up transformer with a single winding that is tapped into. They are called autotransformers in other applications. A sort of go-no-go test is made with an Ohm Meter. The resistance between the 2 small posts is usually less that 5 ohms. I think the stock Fiat coil is about 3 ohms. Be sure to put you meter leads together and see if your meter indicates zero when making this test. If it is a digital meter and indicates something like 0.7 that is the resistance of the leads and you would subtract that from your measurement. The resistance between the distributor contact on the coil and either of the other coil posts should be somewhere around 8000 to 10,000 ohms.
I agree with installing ring terminals. I have done this with all the grounds also. Prior to this year I worked in Aviation and purchased all my crimp terminals from the shop supply house. I recently purchased some crimp terminal on-line and was surprised that the material they were made of was far inferior. I could not make a crimp that I could not pull apart with my hands. The metal for the crimp ares was too thin to maintain the required force on the wire after crimping. I would suggest making a test crimp on a wire off the car to be sure you have good terminals. A good crimp can not be pulled of the wire after its crimped.

Thanks! I will test the coil tonight and compare with those values, after I clean the posts.

I had the same problem with crimps. I bought a fancy crimper and was still able to pull apart the crimps. It actually didn't occur to me that the problem might lie with the metal in the connectors.

The connectors on the two small posts are, as I said, loose and corroded. How might this have affected the performance of the engine (even if the coil was OK)? We've owned the car for 2 years and have experienced only one backfire. The engine has been running quite well since I had the AFM refurbished. Would bad coil post connections cause gas wasting and poor gas mileage in our cars?

Having examined the connections, I'm surprised the engine was running at all.

[KevAndAndi]

Resistance between two posts was 0.7 ohms. Resistance between posts and distributor wire connector was 11,000 ohms.

[spider2081]

I have a spare coil so I checked it this morning. It is not a Magneti marrelli (original) but a replacement.
The post to post measurement was 1 ohm and the post to distributor reading was 9000 ohms.
I don't have a lot of confidence that resistance measurements below a few ohms are real accurate.
I think your coil is good. While you are cleaning things up you might remove the electronic control module that is mounted under the coil in the heat sink. Clean the old heat transfer grease off and install some new grease. The grease dries out and looses it effectiveness with time.

Here is an old IAP video on testing a coil https://video.search.yahoo.com/search/v ... tion=click

[KevAndAndi]

Where exactly do you apply the heat transfer grease?

[spider2081]

The grease is applied to the underside metal surface of the ECM and to the surface of the heat sink it will mate to. When you remove the ECm you will see where the grease is or was.

[KevAndAndi]

The grease is applied to the underside metal surface of the ECM and to the surface of the heat sink it will mate to. When you remove the ECm you will see where the grease is or was.

Got it thanks; ordering some heat transfer grease now.