Starter motor - testing in the car

Note: Refer to the precautions given in Safety first! and in Section 1 of this Chapter before proceeding.

1 If the starter motor fails to operate when the ignition key is turned to the appropriate position, the possible causes are as follows.

a) The battery is faulty.

b) The electrical connections between the switch, solenoid, battery and starter motor are somewhere failing to pass the necessary current from the battery through the starter to earth.

c) The solenoid is faulty.

d) The starter motor is mechanically or electrically defective.

2 To check the battery, switch on the headlamps. If they dim after a few seconds, this indicates that the battery is discharged - recharge (see Section 3) or renew the battery. If the headlamps glow brightly, operate the starter switch and observe the lamps. If they dim, then this indicates that current is reaching the starter motor, therefore the fault must lie in the starter motor. If the lamps continue to glow brightly (and no clicking sound can be heard from the starter motor solenoid), this indicates that there is a fault in the circuit or solenoid - see the following paragraphs. If the starter motor turns slowly when operated, but the battery is in good condition, then this indicates either that the starter motor is faulty, or there is considerable resistance somewhere in the circuit.

3 If a fault in the circuit is suspected, disconnect the battery leads, the starter/solenoid wiring and the engine/transmission earth strap(s).

Thoroughly clean the connections, and reconnect the leads and wiring. Use a voltmeter or test lamp to check that full battery voltage is available at the battery positive lead connection to the solenoid.

Smear petroleum jelly around the battery terminals to prevent corrosion - corroded connections are among the most frequent causes of electrical system faults.

4 If the battery and all connections are in good condition, check the circuit by disconnecting the wire from the solenoid blade terminal. Connect a voltmeter or test lamp between the wire end and a good earth (such as the battery negative terminal), and check that the wire is live when the ignition switch is turned to the start position. If it is, then the circuit is sound - if not, there is a fault in the ignition/starter switch or wiring.

5 The solenoid contacts can be checked by connecting a voltmeter or test lamp between the battery positive feed connection on the starter side of the solenoid, and earth. When the ignition switch is turned to the start position, there should be a reading or lighted bulb, as applicable. If there is no reading or lighted bulb, the solenoid is faulty and should be renewed.

6 If the circuit and solenoid are proved sound, the fault must lie in the starter motor.

The starter motor can be checked by a Ford dealer or an automotive electrical specialist. A specialist may be able to overhaul the unit at a cost significantly less than that of a new or exchange starter motor.

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