4.6L, 5.4L V-8 Starter Replacement

How to Replace the Starter on a 4.6L or 5.4L Ford F-150

Before assuming that a starter motor/relay is bad, always verify battery condition. A fully charged 12 volt automotive battery in good condition will read ~ 12.7 volts at rest (no load). Any voltage reading in the 12.5 to 12.7 range suggests that the battery is charged and, for all intents and purposes, should be in good condition. It is a common misconception that a battery that reads 12.0 volts is fully charged; at 12.0 volts, a battery is actually significantly discharged. Anything lower than 12 volts may not be enough to turn the engine over. Battery voltage should be checked across the negative and positive terminals using a voltmeter or digital multimeter with no load on the battery; disconnecting the negative battery cable first ensures there is no parasitic draw.

Applicable Model Years: 1997 to 2010 4.6L & 5.4L V-8 equipped Ford F-150
Early 1997 4.6L/5.4L Starter Assembly: Motorcraft SA789RM (Pre 7/15/1996 built date)
1997 - 1998 4.6L/5.4L Starter Assembly: Motorcraft SA848RM
1999 - 2005 4.6L/5.4L Starter Assembly: Motorcraft SA873RM
2007 - 2008 4.6L/5.4L Starter Assembly: Motorcraft SA979RM
2009 - 2010 4.6L/5.4L Starter Assembly: Motorcraft SA974 (new), SA1033RM (reman)

If a battery can be isolated as the problem (i.e. recharging a discharged battery to find that the starter is functioning properly), alternator output should be checked. With the vehicle running at normal operating temperature, read the voltage across the battery terminals. 13.7 to 14.7 volts (+/- a few tenths) at idle is considered an acceptable output range. Anything lower than 13.0 volts suggests alternator output is low. Both ambient and engine temperature may affect alternator output, thus there is a reasonable margin of tolerance in the acceptable output range. An alternator producing low or no output must be replaced. All accessories (lights, A/C, stereo) should be turned off when testing alternator output at idle.

An often overlooked, yet simple problem is loose and/or corroded electrical connections at the battery cables, ground terminal at the engine block/vehicle frame, or at one of the starter solenoid terminals. Verify that all electrical connections are secure and corrosion free.

If a starter does not respond to a fully charged battery, the starter relay/solenoid, starter motor, or both are the likely culprits. On most modern starter designs there is little reason to test the solenoid in hopes of isolating the problem - starter solenoids are incorporated as a part of the starter assembly, which will need to be replaced.

A seemingly strange, but oddly effective method of isolating a starter motor as the culprit is to tap the shell of the motor with a small hammer (or similar blunt object). If the motor then turns over the engine, the starter is failing. This will not work in every instance, but frequently acts a band aid. The science behind this "old school" solution is that a starter motor will fail when a copper winding shears - tapping the motor with a hammer often realigns the winding and closes the circuit. This is only a temporary fix and the starter should be replaced, but keeping a hammer in your vehicle may also save you from being left stranded.

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Starter location

• Disconnect the negative battery cable so that there is no power supplied to the vehicle.

• The starter assembly is mounted to the transmission bellhousing on the passenger side of the vehicle, protruding towards the front of the vehicle parallel to the side of the engine block.

Removing starter solenoid wires

• Remove the red safety cap from the starter solenoid to expose the solenoid terminals (note - the safety cap may have previously fallen off or is otherwise missing, in which case the terminals will already be exposed).

• Remove the cable lugs from the lower left and right terminals - one larger and one small cable. The top lug, which connects the solenoid output terminal to the starter motor, does not need to be removed as the starter motor and solenoid will be removed as one assembly. The large terminal requires a 13mm socket while the small terminal requires a 10mm socket (if the starter has previously been replaced with a non-OEM unit, the terminal nut sizes may differ).

Removing first starter bolt

• A 13mm socket is required to remove the (3) bolts that mount the starter to the transmission bellhousing. The bottom mounting bolt is clearly visible from below the starter and is easily removed.

Reaching difficult starter bolt

• Moving clockwise from the bottom bolt, the next bolt is difficult to see so you'll need to rely primarily on touch to locate it. It can be accessed using a 13mm deep socket and a 6" extension. There is ample space to reach it up-and-over the starter solenoid. Since you'll be locating the bolt blindly, ensure that the socket is absolutely secure on the head of the bolt before attempting to loosen it - you do not want to strip the head!

Removing last starter bolt

• The top bolt is the most difficult to access - you won't be able to see it and its position lacks the space to reach your hand in to feel for it. Once again, a 13mm deep socket and a 6" extension can be used to reach the mounting bolt by positioning the tool up-and-over the starter motor. Be patient in locating the bolt with the socket and ensure the socket is fully seated on the bolt head before attempting to loosen it. Fortunately, none of the mounting bolts should be particularly tight.

• With the mounting bolts removed, the starter slides out of the bellhousing towards the front of the vehicle.

Starter removed from bellhousing

• Once the old starter has been removed, clean the mounting surface and all hardware of any grease, grime, and debris.

• Install the new starter assembly in reverse order - slide the starter in place, tighten down the three mounting bolts, install the wiring to the starter solenoid (small lug to small terminal, large lug to large terminal), and finally reinstall the red safety cap.

• Start the mounting bolts by hand using the socket and extension without a ratchet to prevent cross threading. It is also highly recommended that you thoroughly clean the wire lugs and apply a small amount of dielectric grease to the terminals before reinstalling.