1993 Mustang

Section 03-06: Starting System

1993 Mustang Workshop Manual

DIAGNOSIS AND TESTING

System Inspection

CAUTION: When disconnecting the plastic hardshell connector at the solenoid "S" terminal, grasp the plastic connector and pull lead off. DO NOT pull separately on lead wire.

WARNING: WHEN SERVICING STARTER OR PERFORMING OTHER UNDERHOOD WORK IN THE VICINITY OF THE STARTER, BE AWARE THAT THE HEAVY GAUGE BATTERY INPUT LEAD AT THE STARTER SOLENOID IS "ELECTRICALLY HOT" AT ALL TIMES.

A PROTECTIVE CAP OR BOOT IS PROVIDED OVER THIS TERMINAL THAT MUST BE REPLACED AFTER SERVICING. BE SURE TO DISCONNECT BATTERY NEGATIVE CABLE BEFORE SERVICING STARTER.

Inspect starting system for loose connections.

If system does not operate properly, note condition and continue diagnosis using the symptom chart.
WARNING: WHEN WORKING IN AREA OF THE STARTER, BE CAREFUL TO AVOID TOUCHING HOT EXHAUST COMPONENTS.

STARTER SYSTEM DIAGNOSIS
Condition	Possible Source	Action
Starter solenoid does not pull-in and starter does not crank (Audible click may or may not be heard).	Open fuse.	Check fuse continuity.
	Low battery.	Refer to Section 14-00.
	Inoperative fender apron relay.	Go to Pinpoint Test B.
	Open circuit or high resistance in external feed circuit to starter solenoid.	Go to Pinpoint Test A.
	Inoperative starter.	Replace starter as outlined.
Unusual starter noise during starter overrun.	Starter not mounted flush (cocked).	Realign starter on transmission converter housing.
	Noise from other components.	Refer to Section 00-04. Investigate other powertrain accessory noise contributors.
	Ring gear tooth damage or excessive ring gear runout.	Refer to Section 03-01A (2.3L) or Section 03-01B (5.0L).
	Worn or damaged starter.	Replace starter as outlined.
Starter cranks but engine does not start.	Concern in fuel system.	Refer to Section 10-00.
	Concern in ignition system.	Refer to Section 14-00.
	Engine related concern.	Refer to Section 03-01A (2.3L) or Section 03-01B (5.0L).
Starter cranks slowly.	Low battery.	Refer to Section 14-00.
	High resistance or loose connections in starter solenoid battery feed or ground circuit.	Check that all connections are secure.
	Ring gear runout excessive.	Refer to Section 03-01A (2.3L) or Section 03-01B (5.0L).
	Inoperative starter.	Replace starter as outlined.
Starter remains engaged and runs with engine.	Shorted ignition switch.	Refer to Section 11-05.
	Battery cable touching solenoid 'S' terminal (inoperative or mispositioned cable).	Replace or relocate cable and replace starter as outlined.
	Inoperative starter.	Replace starter as outlined.

PINPOINT TEST A: CHECK STARTER MOTOR

A1 CHECK FOR VOLTAGE TO STARTER
NOTE: Hoist vehicle (if necessary) to access starter solenoid terminals.

CAUTION: Remove plastic safety cap on starter solenoid and disconnect hardshell connector at solenoid 'S' terminal as described under Removal and Installation in this Section.

Key OFF. Transmission in PARK or NEUTRAL.

Check for voltage between starter B+ terminal and starter drive housing.

Is voltage between 12-12.45 volts?

Yes
GO toA2.

No
CHECK wire connections between battery and starter solenoid and the ground circuit for open or short.

A2 CHECK STARTER MOTOR

Key OFF. Transmission in PARK or NEUTRAL.

Connect one end of a jumper wire to the starter B+ terminal and momentarily touch the other end to solenoid 'S' terminal.

Does starter crank?

Yes
CHECK connections from output of fender apron relay to 'S' terminal for open or short.

No
REPLACE starter as outlined.

PINPOINT TEST B: CHECK FENDER APRON RELAY

B1 CHECK FENDER APRON RELAY

Key in START. Transmission in PARK or NEUTRAL.

Check for continuity between fender apron relay car ground and a good chassis ground.

Is there continuity?

Yes
GO to B2 .

No
SERVICE ground. GO to B2 .

B2 CHECK VOLTAGE AT FENDER APRON RELAY START TERMINAL

Key in START. Transmission in PARK or NEUTRAL.

Check for voltage between fender apron relay start terminal and case ground.

Is voltage between 12-12.45 volts?

Yes
GO to B3 .

No
Open circuit or high resistance exists in external circuit wiring or components. Check the following:

All circuit connections including plastic hard-shell connector at solenoid "s" terminal to make sure it is not broken or distorted.
Ignition switch.
PNP or CPP switch.
Anti-theft contact.

B3 CHECK OUTPUT TERMINAL VOLTAGE

Key in START. Transmission in PARK or NEUTRAL.

Check for voltage at output terminal of fender apron relay.

Is voltage OK?

Yes
REFER to Starter System Diagnosis condition chart in this section.

No
REPLACE fender apron relay as outlined.

Starter Load Test

Tools Required:

Rotunda Starting/Charging Tester 078-00005

Conduct this test if the starter cranks slowly and it is desired to compare current to specifications.

Connect Rotunda Starting and Charging Tester 078-00005 or equivalent. Make sure that current is not flowing through ammeter and heavy-duty carbon pile rheostat portion of circuit (rheostat at maximum counterclockwise position).

Place transmission in NEUTRAL or PARK. Crank engine with ignition off, and determine exact reading on voltmeter.
This test is accomplished by disconnecting push-on connector 'S' at starter relay and by connecting a remote-control starter switch from positive battery terminal to 'S' terminal of starter relay.
NOTE: Make sure ignition switch is in the OFF position and 'S' terminal connector has been removed so engine does not start.

Stop cranking engine, and reduce resistance of carbon pile until voltmeter indicates same reading as that obtained while starter cranked the engine. The ammeter will indicate starter current draw under load. Check this with value listed in Specifications.