Coil problems

[Tom Hicks]

I have four coils rebuilt back in the fall of '17 by a reliable rebuilder. He set them up on an ECCT and I put them in Ellie Mae when I put the engine in last winter. They can't have more than 20 hours on them. Miss Ellie was running great, then she started to miss, then I smelled something burning (tar), and after a minute she cut off. Fortunately I live at the bottom of a hill and I made it into the driveway with a little pushing.

My ECCT indicates all four coils have poor capacitors, three won't fire at all, and one fires but not in the good range.

I am running on twelve volts, no magneto, and she was running strong. What would cause catastrophic coil failure like this?

[Scott_Conger]

I'd send one or all back to the rebuilder tell him exactly what configuration you use for ignition (mag/distributor/whatever), and ask for a post-mortem on at least one coil. He will discover what exactly failed and based on the failure mode, should be able to point you to the (potential) cause. A thorough inspection and troubleshooting expedition of the ignition system, including wiring is also due on your end to augment his finding(s). He will likely want to know what you find, if anything. Complete failure of coils in rapid sequence is highly unusual.

[MKossor]

Tom,

Regarding ECCT capacitor test failing on all 4 of your coils. The capacitor test requires the point contacts to be clean and closed making good electrical contact (shorted) at the beginning of the test. You open the points during the test and must make sure you don't touch both point contacts with your fingers or the resistance of your fingers will case the leakage test to read excessive leakage with Poor test result. There are also other false leakage paths that can develop which could skew the capacitor test results. The most important detail in the capacitor test is the capacitor value; it should not read lower than 0.33uF. The nominal value is 0.47uF and will typically read high (0.56uF -0.68uF) if there is excessive leakage present. Note however, leakage does not significantly effect coil performance so would not replace capacitors due to higher than normal value.

The fact that 3 of the 4 coils do not generate spark all of a sudden is unusual. I would first confirm the points on all coils are clean and making good electrical contact when at rest (points closed). The single spark dwell time test should actuate the coil points pulling them open which you should be able to see and hear. If that does not happen when you run the test it is further indication the coil points are not making good electrical contact when closed at rest. The capacitor test will also fail (poor result) if the coil points dirty and not making good electrical contact while at rest (points closed) as previously stated.