Starter GMC Cab & Chassis S15

DESCRIPTION

Starter is a 12-volt, 4-pole unit of conventional design and has a solenoid pinion shaft (overrunning clutch) with entire mechanism enclosed within housing. Field assembly consists of 4 series coils or combination of series coils with one more shunt coil. Brush assemblies are completely enclosed within field frame at commutator end so entire starter and drive assembly is protected.

Starter solenoid is flange mounted on drive end housing and has a compression-type return spring located inside solenoid case. Diesel Chevrolet and GMC models use the 27MT starter, which differs only in that it uses a center bearing. All other GM models use 5MT or 10MT starter.

SOLENOID WINDING TESTS

Note. Tests are performed with all leads disconnected from solenoid. Complete tests in minimum amount of time to prevent solenoid from overheating.

Hold-In Winding (All Models)

1. Connect an ammeter, voltmeter, carbon pile and battery into starter circuit. (Scheme 1) Using carbon pile, decrease battery voltage to 10-volts.
2. Ammeter should read 14.5-16.5 amps for GM models. Higher reading indicates winding is shorted or grounded. Lower reading indicates excessive resistance.

Both Windings in Parallel (GM Only)

Using same connections as hold-in winding test, ground "M" terminal and using carbon pile adjust voltage to 10-volts. Amperage draw should be 41-47 amps.

Note. Use carbon pile between battery and "M" terminal if its required to reduce voltage to specified testing voltage. If not, connect jumper directly from battery to "M" terminal.

Connections for Testing Solenoid Windings Dashed lines show connections used for pull-in winding testing. Scheme 1

1. To perform test, connect a tachometer, ammeter and voltmeter into start circuit. (Scheme 2) Adjust carbon pile to specified voltage indicated in «STARTER NO-LOAD SPECIFICATIONS»(/gmc/cab-chassis-s15/1985-1988/remont/starter/#starter).
2. Read current draw and armature speed to ensure they are within specifications. DO NOT apply voltage greater than specified, as excessive voltage may cause armature to throw windings due to excessive speed.
3. Low free speed and high current draw indicates too much friction, shorted armature, or grounded armature or fields. Failure to operate with high current draw indicates a direct ground in terminal or fields, or frozen bearings.
4. Failure to operate with no current draw indicates the following: an open field, open armature coils, broken brush springs, worn brushes, or high commutator insulation.
5. If no-load speed is low and there is low current draw, suspect high internal resistance due to poor connection, defective leads, or dirty commutator. A high free speed and high current draw usually indicates shorted fields.

Connections for No Load Test Use fully charged battery to make proper test. Scheme 2

Armature

Test armature for shorted coils with a growler. Check for grounded coils using a self-powered test light. Place one test lead on armature core or shaft, and other test lead on commutator. Lamp should not light. If lamp lights, armature is grounded and should be replaced.

Field Coils

1. Using self-powered test light, place one test lead on field coil terminal strap, and touch other test lead to field coil brush lead (check series coils and shunt coils separately at appropriate terminals).
2. Lamp should light. If lamp does not light, coils are open. Check for grounds by placing one test lead on field armature strap, and touch other lead to armature core or shaft. If lamp lights, one or more coils are grounded.

Replace brushes if worn to 1/2 of original length, or if oil-soaked or pitted. Check brush spring tension and replace springs if weak or distorted. Deformed or bent brush holders can be replaced by service units which are installed with screws and nuts.

Drive & Pinion

Pinion should turn freely in overrun direction and should not slip in drive direction. Check spring for correct tension and drive collar for wear (these parts can be removed for replacement by forcing collar toward clutch and removing lock ring from end of tube). Replace drive assembly if pinion teeth are worn, chipped, or cracked.

Pinion Clearance

1. Disconnect motor field coil connector and insulate it carefully. Connect a battery from solenoid switch terminal to solenoid frame. Momentarily flash a jumper lead from motor terminal to solenoid frame.
2. This shifts pinion into cranking position. Push pinion back toward commutator end to eliminate slack. Measure distance between pinion and pinion stop. When installing starter, check clearance between pinion and flywheel ring gear teeth. Refer to the «PINION CLEARANCE»(/gmc/cab-chassis-s15/1985-1988/remont/starter/#starter) .
3. Insert .020" (.6 mm) diameter wire, about 3" (76 mm) long, with a 1/4" to 1/2" 90° bend in end between pinion tooth and ring gear. Center pinion tooth between flywheel teeth when making measurement.

REMOVAL & INSTALLATION

Note. If shims are installed between starter and engine, note and record the arrangement for installation reference.

"T" SERIES

1. Disconnect negative battery cable. Raise and support vehicle. Disconnect electrical wiring from starter solenoid. Remove mounting bracket and wiring from brush end of starter. Remove skid plate. Remove 2 brake line-to-crossmember brackets.
2. Remove 6 crossmember bolts and remove crossmember. Remove transmission cooler line-to-flywheel housing bracket. Remove brace rod to flywheel housing. Remove lower flywheel housing cover (if necessary).
3. Remove starter bolts. Note location and number of shims for reassembly. Remove starter. To install, reverse removal procedure. Tighten bolts and nuts to specifications. See «TORQUE SPECIFICATIONS»(/gmc/cab-chassis-s15/1985-1988/remont/starter/#starter) .

"U" SERIES

1. Disconnect negative battery cable. Raise and support vehicle. Remove nut from A/C bracket. Remove engine bracket nut and bracket. Place drain pan under oil pan. Remove oil pressure sending unit. Remove oil filter.
2. Disconnect electrical wiring from starter. Remove starter bolts. Note location and number of shims for reassembly. Remove starter. To install, reverse removal procedure. Tighten bolts and nuts to specifications. See «TORQUE SPECIFICATIONS»(/gmc/cab-chassis-s15/1985-1988/remont/starter/#starter) .

EXCEPT "T" & "U" SERIES

1. Disconnect negative battery cable. Raise and support vehicle. Remove starter braces and shields (if equipped). Remove brush end mounting bracket (if equipped). Disconnect electrical wiring from starter solenoid.
2. Remove starter mounting bolts. Remove shims and note arrangement for reassembly. Remove starter. To install, reverse removal procedure. Ensure shims are installed in original location. Tighten bolts or nuts to specifications. See «TORQUE SPECIFICATIONS»(/gmc/cab-chassis-s15/1985-1988/remont/starter/#starter) .

DISASSEMBLY

1. Disconnect field coil connector from solenoid motor terminal. Remove solenoid mounting screws and rotate solenoid 90°. Remove solenoid and solenoid plunger spring.
2. Remove 2 through bolts, commutator end frame, field frame assembly and washer. On diesel models, remove insulator. On gasoline models, remove armature assembly from drive housing and thrust collar from armature shaft.
3. On diesel models, remove shift lever pivot bolt, center bearing screws and drive gear housing from armature shaft. Shift lever and plunger assembly will now fall away from starter clutch.
4. On gasoline models, slide a 5/8" deep socket over pinion shaft and with a hammer, strike socket against retainer to drive retainer off snap ring. Remove snap ring from groove in armature shaft.
5. On diesel models, remove retainer, clutch assembly, fiber washer and center bearing. Remove roll pin and remove shift lever and plunger. On gasoline models, roller clutches are serviced as an assembly only.

CLEANING

Clean all parts by wiping with clean cloth. DO NOT clean armature, field coils, or drive assembly in any type of grease dissolving solvent as this will damage insulation and wash lubricant out of drive assembly.

Scheme 3

Scheme 4

1. On diesel model starters, assemble armature and clutch as follows: lubricate drive end of armature shaft with silicone lubricant and install center bearing, fiber washer and clutch assembly onto armature, with pinion away from armature. Slide retainer onto shaft and install snap ring and thrust washer. (Scheme 3): Checking Pinion-to-Housing Clearance Force gear rearward to eliminate slack.
2. Position retainer and thrust washer with snap ring in between. Using pliers, grip retainer and washer and squeeze until snap ring is forced into retainer and is held in groove in armature shaft.
3. On all models, lubricate drive gear housing bushing with silicone lubricant. Engage shift lever yoke with clutch and slide complete assembly into drive gear housing. (Scheme 4): Exploded View of Delco-Remy 27MT Starter Assembly The 5MT and 10MT starters are similar but have no center bearing.
4. Install center bearing screws and shift lever pivot bolt. Tighten securely. Install solenoid assembly on drive gear housing. Apply sealer (No. 1050026) to solenoid flange where it meets drive housing and field frame, using care not to damage brushes.
5. Position field frame against drive gear housing on alignment pin, using care not to damage brushes. Lubricate commutator end frame bushing with silicone lubricant. Install washer on armature shaft and slide end frame onto shaft and install through bolts.
6. On diesel models, install insulator and then end frame onto shaft. Install through bolts, making sure they pass through bolt holes in insulator. Connect field coil connector to solenoid terminal. Check pinion clearance as outlined in OVERHAUL and TESTING.

Exploded View of Shift Lever Assembly. Scheme 5

STARTER NO-LOAD SPECIFICATIONS (1)

PINION CLEARANCE

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

See also:
• STARTER NO-LOAD SPECIFICATIONS