Primary And Secondary Timing Chains

WARNING: This page is about a different car, the 2019 Jaguar XE. However, it is still accessible from the selected car via links, so may be relevant.

Courtesy of JAGUAR LAND ROVER NORTH AMERICA, LLC

ITEM	DESCRIPTION
1	Timing chain tensioner assembly - Bank 1
2	Timing chain tensioner arm - Bank 1
3	Primary timing chain - Bank 1
4	Timing chain guide - Bank 1
5	Variable Camshaft Timing (VCT) actuator assembly - Bank 1 exhaust camshaft
6	VCT actuator assembly - Bank 1 intake camshaft
7	Exhaust camshaft - Bank 1
8	Intake camshaft - Bank 1
9	Intake camshaft - Bank 2
10	Exhaust camshaft - Bank 2
11	VCT actuator assembly - Bank 2 exhaust camshaft
12	Timing chain guide - Bank 2
13	Primary timing chain - Bank 2
14	Timing chain tensioner arm - Bank 2
15	Timing chain tensioner assembly - Bank 2
16	VCT actuator assembly - Bank 2 intake camshaft
17	Secondary timing chain
18	Fuel pump camshaft
19	Secondary timing chain guide
20	Crankshaft sprocket
21	Secondary timing chain tensioner
22	Oil pump sprocket

Double overhead camshafts on each cylinder head operate the valves. Graded tappets enable setting of intake and exhaust valve clearances.

The 2, endless, simplex roller, primary timing chains are used to drive the camshafts, 1 chain for each cylinder bank. The primary timing chains are driven from a crankshaft sprocket and are passed over 2 sprockets which are integral with the Variable Camshaft Timing (VCT) actuator assemblies.

A procedure is required to make sure that the correct crankshaft to camshaft timing is achieved.

For additional information, Refer to: ENGINE .

Each primary timing chain has a fixed timing chain guide which is secured to the cylinder block with 3 shoulder bolts. The chain guides are controls the chain motion on the drive side. A tensioner arm is installed to each timing chain which can rotate around a shoulder pivot bolt.

Each primary timing chain has a hydraulic chain tensioner operated by engine oil pressure. The chain tensioner maintains the primary timing chain at the correct tension and dampens backlash in the chain tension due to engine deceleration. Each primary timing chain tensioner also incorporates a mechanical tensioner operated by spring tension to maintain the tension while the engine is stopped to eliminate start-up noise.

Each timing chain tensioner has a hole which allows for the locking of the tensioner to facilitate removal of the tensioner arm, guide or camshaft timing chain. The tensioner plunger can be pushed back into the housing and a pin inserted to lock the tensioner in the retracted position.

The timing chains are lubricated with engine oil from jets located at the front of the engine block. The timing chains and tensioners are maintenance free components.

The fuel pump camshaft is located on 3 machined bosses on the windage tray and secured with a camshaft carrier which is secured to the windage tray with 8 bolts. The 2 lobes on the camshaft act through tappets, located in the camshaft carrier, against a plunger on each single cylinder High Pressure (HP) fuel pump.

For additional information, Refer to: FUEL CHARGING AND CONTROLS .

The camshaft is installed with a drive sprocket which is a press fit on the camshaft. The sprocket is timed to the cam lobes to match the HP fuel pump delivery strokes with crankshaft position and therefore must not be removed. The sprocket also drives the vacuum pump via a drive coupling.

For additional information, Refer to: BRAKE BOOSTER - PROJECT 8 .

The fuel pump camshaft is driven at crankshaft speed by the secondary timing chain, which also drives the variable flow oil pump from the crankshaft sprocket.

A tensioner arm is installed to the secondary timing chain. The tensioner arm can rotate around a shoulder pivot bolt which is secured to the windage tray. The tensioner arm comprises a spring, which applies a controlled tension to the secondary timing chain. This maintains the timing chain at the correct tension and allows for and dampens backlash in the chain tension due to engine deceleration.

The secondary timing chain has a fixed timing chain guide. The chain guide is secured to the front main bearing cap with a roll pin and a screw. The chain guide controls the chain motion on the drive side.