Starting System: Notes

2010 Ford Focus S, StandardSECTION Notes
WARNING: This page is about a different car, the 2010 Mercury Mariner and 2010 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

The starting system consists of the following:

  • Starter motor
  • Starter motor relay
  • Transmission Range (TR) sensor (automatic transaxle)
  • Clutch cutoff switch (manual transaxle)
  • Battery
  • Ignition switch
  • PCM
  • Start diode

When the starter solenoid is energized, a magnetic field is created in the starter solenoid windings. The iron plunger core is drawn into the starter solenoid coil, and a drive lever and pin connected to the starter drive engages the drive pinion gear to the flywheel ring gear. When the plunger is pulled all the way in, its contact disc closes the circuit between the battery and the motor feed terminals. This sends current to the motor, and the drive pinion gear cranks the flywheel to start the engine. When current flows to the starter motor, the starter solenoid pull-in coil is bypassed, and the hold-in coil keeps the drive pinion gear engaged with the flywheel.

An overrunning clutch in the starter drive protects the starter motor from excessive speeds during the brief period before the driver releases the ignition switch from the START position as the engine starts.

Vehicles equipped with a manual transaxle have a clutch cutoff switch mounted on the clutch pedal bracket. The clutch cutoff switch prevents operation of the starter motor unless the clutch pedal is fully depressed.

Vehicles equipped with an automatic transaxle have a TR  sensor mounted on the transaxle. The TR  sensor prevents operation of the starter motor unless NEUTRAL or PARK is selected.

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.