The ECM determines how long the glow plugs are energized after the ignition switch is turned to «ON», as well as the glow time of the control lamp for the operation of the diesel engine preheating system, depending on the temperature of the engine coolant.
When the ECM detects a failure, it sets the error code corresponding to the failure (associated with the fuel supply system).
Checking the diesel engine preheating system
1. Check the battery voltage, which should be between 11-13V.
2. Make sure that the engine coolant temperature is not higher than 40°C.
Pic. 9.40. Resistance measurement between wire (1) and glow plug housing
3. Measure the resistance between wire and glow plug body («weight») as shown in fig. 9.40.
Attention! The resistance value is the resistance of two glow plugs connected in parallel.
The nominal resistance value is 0.3 ohm.
Pic. 9.41. Measuring resistance at the contacts of the glow plug relay connector: «1» – «2» – relay 1 (glow plugs 1 and 3); «1» – «3» – relay 2 (glow plugs 2 and 4)
4. Measure voltage from relay 1 side (glow plugs 1 and 3) and on the relay side 2 (glow plugs 2 and 4) (pic. 9.41).
When measuring from the relay 1 side of the glow plugs, connect an ohmmeter to the wire of the glow plug of the third cylinder and to the housing («mass») third cylinder glow plugs.
When measuring from the relay side of the 2 glow plugs, connect an ohmmeter to the 4th cylinder glow plug wire and to the body («mass») glow plugs of the fourth cylinder.
5. Measure the voltage immediately after turning on the ignition (without engine start).
Voltage rating is 9-11V (voltage decreases to 0 V within 11–22 s).
6. Be convinced also that the control lamp of glow plugs lights up right after inclusion of ignition.
Attention! «Conduction time» current varies depending on the temperature of the coolant when the ignition is on.
7. Measure tension during cranking by a starter of a cranked shaft of the engine.
The nominal voltage value is at least 6 V.
8. Start the engine and measure the voltage while the engine is warming up.
9. The voltage always decreases to 0 V within 10-220 seconds after the engine is started.
The voltage rating is 12-15V.
Checking the Glow Plug Relay Box
1. Disconnect the glow plug wire and all other connectors from the glow plug relay.
2. Measure the resistance across the contacts «1» – «2» and on «1» – «3» glow plug relay connector (see fig. 9.41).
The nominal resistance value is 27-35 ohms.
3. Check the operation of the glow plug relay.
When testing relay 1, connect «+» battery to contact «1» connector, and «–» battery to contact «2» relay connector.
When testing relay 2, connect «+» battery to contact «1» connector, and «–» battery to contact «3» relay connector.
Attention! Do not ground the terminals of disconnected connectors.
When using jumpers, be especially careful not to mix up the connected terminals. This leads to failure of the relay.
4. Check for continuity on each pin when the jumper «+» battery is connected and disconnected.
When testing relay 1, connect an ohmmeter to the terminals «1» And «A» (glow plug wire 3) single pin connector.
When testing relay 2, connect an ohmmeter to the terminals «1» And «IN» (glow plug wire 4) single pin connector.
When connected «+» battery chain (conductance between contacts) closed, and when disconnected, the circuit is open.
Glow plug
Removing
1. Remove the fuel injectors.
Pic. 9.42. F8QT engine glow plugs: 1 – wire harness connector; 2 - glow plug, 22.5 Nm
2. Disconnect harness 1 electrical connector (pic. 9.42, 9.43).
Pic. 9.43. F9Q Engine Glow Plugs: 1 - connection of the glow plug wire connector; 2 - glow plug
3. Unscrew glow plugs.
Installation
Installation is carried out in the reverse order of removal.