Pic. 4.20. Scheme of the drive chain with one camshaft: 1 - camshaft gear; 2 - chain damper; 3 - gear wheel of the high-pressure fuel pump drive; 4 - chain damper; 5 - oil pump chain tensioner; 6 - oil pump drive gear; 7 - crankshaft gear; 8 - shoe of the tensioner of the control chain; 9 - hydraulic tensioner
The camshafts are driven by the crankshaft via a two-row chain (the so-called duplex circuit). The camshaft gear has twice as many teeth as the crankshaft gear. Therefore, the camshaft speed is half the crankshaft speed (pic. 4.20). With unregulated (stretched) the side of the chain is limited by a special plate (chain damper), on the other hand, it is pressed by the tensioner shoe.
Checking chain wear
Pic. 4.21. Checking chain wear
If noise occurs, check the condition of the circuit (pic. 4.21). When worn, the chain lengthens. This elongation wears the camshaft gear. In the worst case, the gear teeth can break and the chain will slip, causing severe engine damage.
If the chain is checked in time and its wear is detected, it is enough to replace the chain and camshaft gear. In case of severe wear, it is necessary to replace all parts of the chain drive. This work is carried out at the service station by specialists.
Chain tensioner
Located on the right side of the cylinder head. Through the shoe, the tensioner presses on the chain. Its force is the sum of the force of the built-in spring and the pressure of the oil passing through the tensioner. The oil in the tensioner also smooths out the stress when the chain is pulled hard.
A defective tensioner must be replaced. Lubricate the new tensioner with engine oil.