Ford Motorcraft Starter With Integral Positive Engagement Drive

Fig. 1 Ford Motorcraft positive engagement starting motor. 4-140 & 4-97.6 engines (Typical):

Fig. 2 Ford Motorcraft positive engagement starting motor. Except 4-140 & 4-97.6 (Typical):

Fig. 3 Starter drive engaged:

DESCRIPTION
This type starting motor, Figs. 1 and 2, is a four pole, series parallel unit with a positive engagement drive built into the starter. The drive mechanism is engaged with the flywheel by lever action before the motor is energized. When the ignition switch is turned on to the start position, the starter relay is energized and supplies current to the motor. The current flows through one field coil and a set of contact points to ground. The magnetic field given off by the field coil pulls the moveable pole, which is part of the lever, downward to its seat. When the pole is pulled down, the lever moves the drive assembly into the engine flywheel, Fig. 3. When the moveable pole is seated, it functions as a normal field pole and opens the contact points. With the points open, current flows through the starter field coils, energizing the starter. At the same time, current also flows through a holding coil to hold the movable pole in its seated position. When the ignition switch is released from the start position, the starter relay opens the circuit to the starting motor. This allows the return spring to force the lever back, disengaging the drive from the flywheel and returning the movable pole to its normal position.

Fig. 4 Diagnosis chart:

DIAGNOSIS
When diagnosing this starter motor, refer to Fig. 4.

Fig. 5 Starter cranking circuit test connections:

IN-VEHICLE TESTING
Disconnect vacuum line to thermactor bypass valve before performing any cranking tests. After tests, run engine 3 minutes before connecting vacuum line.
Starter Cranking Circuit Test
1. Make test connections as shown in Fig. 5.
2. Disconnect ignition coil and crank engine.
3. Connect remote control starter switch from battery terminal of starter relay to S terminal of relay.
4. Maximum allowable voltage drop should be as follows:
a. .5 volt with voltmeter negative lead connected to starter terminal and positive lead connected to battery positive terminal.
b. .1 volt with voltmeter negative lead connected to starter relay (battery side) and positive lead connected to positive terminal of battery.
c. .3 volt with voltmeter negative lead connected to starter relay (starter side) and positive lead connected to positive terminal of battery.
d. .3 volt with voltmeter negative lead connected to negative terminal of battery and positive lead connected to engine ground.

Fig. 6 Starter load test connection. Positive engagement starter:

Starter Load Test
1. Connect test equipment as shown in Fig. 6.
2. Ensure that no current is flowing through ammeter and heavy duty carbon pile rheostat portion of circuit.
3. 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.
4. Stop cranking engine and reduce resistance of carbon pile until voltmeter indicates same reading as that obtained while starter cranked engine. Ammeter should read 150---250 amps.