Detroit Diesel Troubleshooting Diagrams

An improved vehicle engine sensor harness which virtually eliminates the potential for wire chafing damage has replaced the former harness on all Detroit Diesel Series 60 DDEC II engines. This change took effect approximately October 30, 1992

Detroit Diesel has found instances of chafing on the sensor connector harness (part number 8929468) used on DDEC II engines. The chafing can occur at the end of the plastic tee-coupling where the wires from the 30-way connector enter the coupling.  The chafing results from the absence of abrasion-resistant, convoluted tubing around the wires. Installing convoluted tubing is impractical due to the shortness of the wires at this point. With no abrasion-resistant material surrounding the wires, the rough plastic ridges inside the leg of the tee-coupling can cut through the wire coatings, exposing the wires to moisture and potential shorting. Shorting can result in the logging of false DDEC trouble codes. ‪

The DDEC III/IV engine sensor harness for vehicle engines was originally equipped with five metal retaining clips and was secured to the engine cylinder block with bolts. Effective with engines built in May of 1995, three of the metal clips were replaced by three plastic push-in clips.

Due to a hardware change made in October of 1995 to the DDEC ^® III ECM, a path to ground can arise during ECM powerdown which may allow unintended engine cranking. ‪

Unintended engine cranking can occur if all of the following conditions exist: ‪

• The engine has an ECM manufactured between October of 1995 and September of 1996.
• The engine is equipped with the Optimized Idle ^™ feature.
• The ignition remains turned on while battery power is removed from the ECM during servicing.

Note: This condition will not occur on engines manufactured after September of 1996.

To address this concern and eliminate the potential for unintended engine cranking under the conditions listed above, an Optimized Idle Starter Relay Harness Overlay Service Kit was released for engines with ECM’s manufactured between October of 1995 and September of 1996. ‪

The tachometer drive is driven off the head of the camshaft drive gear retaining bolt, which must be of the slotted configuration, and mates with the blade of the tachometer drive unit. The tachometer drive unit is driven at half crankshaft speed. A tachometer drive adaptor is attached to the drive.

The Series 60 engine can be configured with or without a mechanical tachometer drive. A camshaft drive gear access cover mounted to the gear case cover and a slotted head camshaft bolt must be used with the mechanical tachometer drive option.

The cranking circuit may contain a key start switch or push switch (or both), a relay, magnetic switches, solenoids, oil pressure switch, fuel pressure switch, and other protective devices. For the complete cranking circuit, refer to the vehicle manufacturer’s wiring diagram.

A solenoid, mounted on the cranking motor housing, operates the over-running clutch drive by linkage and a shift lever. When the start switch is closed, the magnetic switch contacts close, and the solenoid windings are connected to the battery. The resulting plunger and shift lever movement causes the pinion to engage the engine flywheel ring gear and the solenoid main contacts to close, and the cranking takes place.

When the cranking circuit is closed, a drive pinion on the armature shaft engages with the teeth on the engine flywheel ring gear to crank the engine. When the engine starts, it is necessary to disengage the drive pinion to prevent the armature from overspeeding and damaging the cranking motor. To accomplish this, the cranking motor is equipped with an over-running clutch within the drive pinion. The cranking motor drive pinion and the engine flywheel ring gear must be matched to provide positive engagement and to avoid clashing of the gear teeth. ‪

Note: Some engines may be equipped with air starters. Contact starter manufacturer for operating characteristics and rebuilding procedures.

The 42 MT cranking motor typically used on the engine has a nose housing that can be rotated to obtain a number of different solenoid positions with respect to the mounting flange. The commutator end cap can be removed to inspect the brushes, in most cases, without removing the cranking motor from the vehicle. ‪

Note: The 50 MT cranking motor is used on heat exchanger-cooled pleasure craft marine engines.

The cranking motor armature is supported by three sintered bronze bearings located, one each, in the nose and intermediate housings, with one in the commutator end cap.

The cranking motor is bolted to the flywheel housing.

Detroit Diesel has released a new alternator mounting bracket for the Series 60 2002 Engine, mounting bolt torque specifications remain standard.

The battery charging alternator provides a source of electrical current for maintaining the storage battery in a charged condition and supplies sufficient current to carry any other electrical load requirements up to the rated capacity of the alternator. ‪

The battery charging circuit consists of an alternator, with an integral voltage regulator, a battery(s) and the connecting wiring.