Variable Camshaft Timing Unit Schematic - Base Timing
WARNING: This page is about a different car, the 2019 Jaguar XJ and 2018 Jaguar XJ. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
Intake camshaft VCT
unit shown. For exhaust camshaft VCT
unit, read advance for retard and retard for advance.
| ITEM | DESCRIPTION |
|---|---|
| 1 | Advance chamber |
| 2 | Retard chamber |
| 3 | Sprocket housing |
| 4 | Rotor assembly |
| 5 | Lock pin |
| 6 | Sleeve |
| 7 | Engine oil supply from camshaft |
| 8 | Inlet check valve |
| 9 | Lock pin drain |
| 10 | Spool valve |
| 11 | Advance check valve |
| 12 | Retard check valve |
NOTE:
The following description is for intake camshaft VCT
units. For exhaust camshaft VCT
units, read advance for retard, and retard for advance.
At engine start-up, once the engine oil pressure in the camshaft is sufficient to open the inlet check valve, engine oil flows across the spool valve, through the advance and retard check valves and into the advance and retard chambers. During the start cycle, the ECM signals the VCT solenoid to move the spool valve into the sleeve and connect the lock pin to inlet oil pressure. The inlet oil pressure causes the lock pin to retract from the inner plate and unlock the rotor assembly and camshaft from the sprocket housing.
There is a constant supply of oil to the VCT to ensure the unit remains filled during operation.