If you are thinking weak spark, check the 12 VDC power to the coils. Coils are designed to operate with 12 VDC and anything less reduces the efficiency and effectiveness of the spark. Old wire and parasitic losses from other items being supplied from the same wire reduces the voltage to the coils. If you do not have 12 VDC at the coils, or as close as possible, you may want to run a new switched 12 VDC supply to the coils.