Multiple coil failures


Well-Known Member
Hi, had my 3rd one fail after only 3 days this time, any ideas? What happens is the car runs but misfires intermittently on acceleration. I fit a new coil and all is well. Repeat. The last Bosch coil lasted 8 months. I'm running a 35DLM8 with the side mounted switching module and a 3 ohm coil with no ballast, which is correct for this.


Active Member
If the 35DLM8 is the SD1 type with a reluctor pickup, here's my experience. A few years old it developed a misfire while warming up. It was on a consistent cylinder, not the plug, not the lead, not the cap. The specified gap (14-16 thou) from the rotating thing with magnets in its edge was at 16, so I closed it to 14 and the problem went away - a single weak magnet? Whats happening to the coils - winding failure?


Well-Known Member
If every thing is as it should be, ie right coil right ballast or no ballast as the case maybe then it could come down to plug leads or plugs.

When you change out to a new coil and everything goes correctly for a time then failures maybe due to inter-winding break-over in the coil causing low output volts and poor firing as the result.

If a lead is too high a resistance and or the plug is tending more toward a higher flash-over point then the coil is at risk of operating closer to open circuit which will then means the unloaded voltage of the coil is much higher possibly leading to inter-winding break-over and eventual failure....... Just my two cents.