See Figures 1, 2 and 3
The starter is located on the left side (2.5L) or right side (4.3L) of the engine. The 1985-87 2.5L is equipped with a 5MT starter. The 4.3L is equipped with a 10MT. In the model year 1988, the names of the 5MT changed to SD-200 and the 10MT changed to the SD-300. The starters are basically still the same.
The starting motor is a specially designed, direct current electric motor capable of producing a very great amount of power for its size. One thing that allows the motor to produce a great deal of power is its tremendous rotating speed. It drives the engine through a tiny pinion gear (attached to the starter's armature), which drives the very large flywheel ring gear at a greatly reduced speed. Another factor allowing it to produce so much power is that only intermittent operation is required of it. This (little allowance for air circulation is required) and the windings can be built into a very small space.
The starter solenoid is a magnetic device which employs the small current supplied by the starting switch circuit of the ignition switch. This magnetic action moves a plunger which mechanically engages the starter and electrically closes the heavy switch which connects it to the battery. The starting switch circuit consists of the starting switch contained within the ignition switch, a transmission neutral safety switch or clutch pedal switch, and the wiring necessary to connect these in series with the starter solenoid or relay.
A pinion, which is a small gear, is mounted to a one-way drive clutch. This clutch is splined to the starter armature shaft. When the ignition switch is moved to the start position, the solenoid plunger slides the pinion toward the flywheel ring gear via a collar and spring. If the teeth on the pinion and flywheel match properly, the pinion will engage the flywheel immediately. If the gear teeth butt one another, the spring will be compressed and will force the gears to mesh as soon as the starter turns far enough to allow them to do so. As the solenoid plunger reaches the end of its travel, it closes the contacts that connect the battery and starter and then the engine is cranked.
As soon as the engine starts, the flywheel ring gear begins turning fast enough to drive the pinion at an extremely high rate of speed. At this point, the one-way clutch begins allowing the pinion to spin faster than the starter shaft so that the starter will not operate at excessive speed. When the ignition switch is released from the starter position, the solenoid is de-energized, and a spring contained within the solenoid assembly pulls the gear out of mesh and interrupts the current flow to the starter.
Some starter employ a separate relay, mounted away from the starter, to switch the motor and solenoid current on and off. The relay thus replaces the solenoid electrical switch, buy does not eliminate the need for a solenoid mounted on the starter used to mechanically engage the starter drive gears. The relay is used to reduce the amount of current the starting switch must carry.
- Dead battery.
Open starter circuit, such as:
- Broken or loose battery cables.
- Inoperative starter motor solenoid.
- Broken or loose wire from ignition switch to solenoid.
- Poor solenoid or starter ground.
- Bad ignition switch.
Defective starter internal circuit, such as:
- Dirty or burnt commutator.
- Stuck, worn or broken brushes.
- Open or shorted armature.
- Open or grounded fields.
Starter motor mechanical faults, such as:
- Jammed armature end bearings.
- Bad bearings, allowing armature to rub fields.
- Bent shaft.
- Broken starter housing.
- Bad starter drive mechanism.
- Bad starter drive or flywheel-driven gear.
Engine hard or impossible to crank, such as:
- Hydrostatic lock, water in combustion chamber.
- Crankshaft seizing in bearings.
- Piston or ring seizing.
- Bent or broken connecting rod.
- Seizing of connecting rod bearings.
- Flywheel jammed or broken.
Starter Spins Freely, Won't Engage
- Sticking or broken drive mechanism.
- Damaged ring gear.
SHIMMING THE STARTER
See Figures 4 and 5
Starter noise during cranking and after the engine fires is often a result of too much or too little distance between the starter pinion gear and the flywheel. A high pitched whine during cranking (before the engine fires) can be caused by the pinion and flywheel being too far apart. Likewise, a whine after the engine starts (as the key is released) is often a result of the pinion-flywheel relationship being too close. In both cases flywheel damage can occur. Shims are available in 0.015 in. sizes to properly adjust the starter on its mount. You will also need a flywheel turning tool, available at most auto parts stores or from any auto tool store or salesperson.
If your truck's starter emits the above noises, follow the shimming procedure below:
- Disconnect the negative battery cable.
- Remove the flywheel inspection cover on the bottom of the bellhousing.
- Using the flywheel turning tool, turn the flywheel and examine the flywheel teeth. If damage is evident, the flywheel should be replaced.
- Insert a screwdriver into the small hole in the bottom of the starter and move the starter pinion and clutch assembly so the pinion and flywheel teeth mesh. If necessary, rotate the flywheel so that a pinion tooth is directly in the center of the two flywheel teeth and on the centerline of the two gears, as shown in the accompanying illustration.
- Check the pinion-to-flywheel clearance by using a 0.5mm (0.020 in.) wire gauge (a spark plug wire gauge may work here, or you can make your own). Make sure you center the pinion tooth between the flywheel teeth and the gauge not in the corners, as you may get a false reading. If the clearance is under this minimum, shim the starter away from the flywheel by adding shim(s) one at a time to the starter mount. Check clearance after adding each shim.
- If the clearance is a good deal over 0.5mm (0.020 in.), in the vicinity of 1.3mm (0.050 in.) plus, shim the starter towards the flywheel. Broken or severely mangled flywheel teeth are also a good indicator that the clearance here is too great. Shimming the starter towards the flywheel is done by adding shims to the outboard starter mounting pad only. Check the clearance after each shim is added. A shim of 0.015 in. at this location will decrease the clearance about 0.010 in.
REMOVAL & INSTALLATION
See Figures 6, 7, 8, 9, 10 and 11
- Disconnect the negative battery cable.
- Raise and support the front of the vehicle on jackstands.
- If equipped, remove any starter braces or shields that may be in the way.
- Disconnect the electrical connectors from the starter solenoid.
- Remove the starter-to-engine bolts, nuts, washers and shims. Allow the starter to drop, then remove it from the engine.
Be sure to keep the shims in order so that they may be reinstalled in the same order.To install:
- Install the starter, shims and bolts. Torque the starter-to-engine bolts to 31 ft. lbs. (42 Nm) for the 2.5L and 28 ft. lbs. (38 Nm) for the 4.3L. Connect the wires to the starter solenoid and the negative battery cable.
- Install any braces or shields if so equipped. Start the engine and check for proper operation.
See Figures 12 and 13
- Remove the starter, then place it on a workbench.
- Remove the screw and the washer from the motor connector strap terminal.
- Remove the two solenoid retaining screws.
- Twist the solenoid housing clockwise to remove the flange key from the keyway in the housing, then remove the housing.
- Place the return spring on the plunger and place the solenoid body on the drive housing. Turn it counterclockwise to engage the flange key.
- Place the two retaining screws in position, then install the screw and washer which secures the strap terminal. Install the unit on the starter.
- Disconnect the field coil straps from the solenoid.
- Remove the through-bolts, then separate the commutator end-frame, the field frame assembly, the drive housing and the armature assembly, from each other.
- Slide the two piece thrust collar off the end of the armature shaft.
- Slide a suitably sized metal cylinder, such as a standard 1 / 2 in. (12.7mm) pipe coupling or an old pinion, onto the shaft so that the end of the coupling or pinion butts against the edge of the pinion retainer.
- Support the lower end of the armature securely on a soft surface, such as a wooden block and tap the end of the coupling or pinion, driving the retainer towards the armature end of the snapring.
- Using a pair of pliers, remove the snapring from the groove in the armature shaft. Then, slide the retainer and the starter drive from the shaft.
- To assemble, lubricate the drive end of the armature shaft with silicone lubricant and slide the starter drive onto the shaft with the pinion facing outward. Slide the retainer onto the shaft with the cupped surface facing outward.
- Again, support the armature on a soft surface, with the pinion at the upper end. Center the snapring on top of the shaft (use a new snapring if the original was damaged during removal). Gently place a block of wood flat on top of the snapring, so as not to move it from a centered position. Tap the wooden block with a hammer in order to force the snapring around the shaft. Then, slide the ring down into the snapring groove.
- Lay the armature down flat on the surface you're working on. Slide the retainer close, up on the shaft, then position it and the thrust collar next to the snapring. Using two pairs of pliers, on opposite sides of the shaft, squeeze the thrust collar and the retainer together until the snapring is forced into the retainer.
- Lubricate the drive housing bushing with a silicone lubricant. Then, install the armature and the clutch assembly into the drive housing, engaging the solenoid shift lever yoke with the clutch and positioning the front of the armature shaft into the bushing.
- Apply a sealing compound, approved for this application onto the drive housing, then, position the field frame around the armature's shaft and against the drive housing.Work slowly and carefully to prevent damaging the starter brushes.
- Lubricate the bushing in the commutator end-frame with a silicone lubricant, place the leather brake washer onto the armature shaft and then slide the commutator end-frame over the shaft and into position against the field frame. Line up the bolt holes, then install and tighten the through-bolts.
- Reconnect the field coil straps to the Motor terminal of the solenoid.
If replacement of the starter drive fails to cure the improper engagement of the starter pinion to flywheel, there are probably defective parts in the solenoid and/or the shift lever. The best procedure would probably be to take the assembly to a shop where a pinion clearance check can be made by energizing the solenoid on a test bench. If the pinion clearance is incorrect, disassemble the solenoid and the shift lever, then inspect and replace the worn parts.Brush Replacement
- Disassemble the starter by following Steps 1 and 2 of the Drive Replacement procedure, above.
- Replace the brushes, one at a time, to avoid having to mark the wiring. For each brush, remove the brush holding screw and the old brush, then position the new brush in the same direction (large end toward the center of the field frame), position the wire connector on top of the brush, line up the holes and reinstall the screw. Make sure the screw is snug enough to ensure good contact.
- Reassemble the starter according to Steps 10-13, above.