What are common steps in oil burner transformer troubleshooting?

Start with safety: shut off power and fuel supply, verify lockout. Check primary power, fuse, and control signal to the ignition transformer. Inspect electrode condition, gap, cracks in porcelain, and grounding. Measure transformer secondary output with the correct HV tester or substitute a known good unit. Check wiring, ignition cable insulation, and burner motor sequence. If spark is weak, intermittent, or absent, confirm proper duty cycle and replace the transformer if output is low or unstable.