Pre Glow System
All engines are equipped with pin-type glow plugs which are connected in parallel. The parallel connection allows glow plugs to operate independently of each other and provides 11 volts to each plug during the preglow process. A dual material heating element which consists of a heating coil and a control coil has allowed the heating process to be shortened to 5-7 seconds at 32°F (0°C). See Fig 1.
These glow plugs are grounded directly to the cylinder head through plug body. Each receives separate power directly from preglow time relay (total initial current draw is approximately 200 amperes).
The preglow time relay is located on the left inner fender of engine compartment. This relay is protected by an 80 ampere fusible link mounted on its cover. It is equipped with a safety cutout circuit to turn off preglow current if no attempt to start vehicle is made within 40-60 seconds after turning ignition to position "2, Preglowing".
Certain malfunctions of preglow system are indicated through preglow indicator light on instrument panel as follows:
- Preglow light blinks for approximately 30 seconds with ignition switch in position "2" - Main power circuit is interrupted. Blown 80 ampere fusible link or defective power relay in preglow time relay.
- Preglow light fails to light but engine can be started - Inspect preglow indicator light circuit and check for open in circuit between temperature sensor and preglow time relay.
- Preglow light blinks for approximately 30 seconds after engine, is started - Disconnect 8-pin plug from preglow time relay and measure ohms between engine ground and harness terminals leading to glow plugs. High or infinite ohm reading indicates open in glow plug, cable to glow plug or terminal connections.