Camshaft Timing Chain

Courtesy of JAGUAR LAND ROVER NORTH AMERICA, LLC

Two bushed timing chains are used to drive the camshafts via an intermediate idler sprocket. The primary camshaft chain is driven by a sprocket on the crankshaft which in turn drives the fuel pump and the intermediate idler sprocket. The fuel pump sprocket is a non-round sprocket that is timed to the crankshaft to reduce chain loads. The secondary camshaft chain is driven by the intermediate idler sprocket and then passed over the sprockets on the inlet and exhaust camshafts. The camshaft sprocket is integral with the VCT actuator assembly.

Each timing chain has a fixed timing chain guide which is secured to the cylinder block. A chain tensioner is fitted to each timing chain which can rotate around a pivot bolt. The primary timing chain has a mechanical tensioner operated by spring tension to apply a controlled tension to the timing chain. The secondary timing chain has a hydraulic secondary chain tensioner which receives pressurized engine oil from the variable flow oil pump with integral vacuum pump. The tensioners maintain the timing chains at the correct tension and allows for and dampens backlash in the chain tension due to engine deceleration. The timing chains and tensioners are maintenance free components.

A procedure and special tools are required to ensure that the correct crankshaft to camshaft timing is achieved. Both the primary and secondary timing chains have gold coloured links which are aligned with timing marks on the sprockets.