The piston of the 1st cylinder is set to the TDC (top dead center) position of the compression stroke so that when carrying out work related to the removal of the camshaft drive belt, the valve timing is not disturbed
If the valve timing is disturbed, the engine will not work normally.
In addition, according to the mark on the camshaft pulley, its position is controlled when adjusting the clearances in the valve drive, setting the phase of complete closing of both valves of the 1st cylinder before adjusting.
For Renault car engines, unlike the engines of most other car brands, the cylinders are counted from the flywheel, and not from the crankshaft pulley.
Set the TDC according to the mark on the camshaft pulley (when setting according to the marks on the crankshaft pulley, the piston of either the 1st or 4th cylinder can be in this position).
After that, be sure to check that the marks on the crankshaft toothed pulley match (with the accessory drive pulley removed).
If the marks on the crankshaft pulley do not match, then the valve timing is incorrect (the piston of the 1st cylinder is not set to TDC).
In this case, it is necessary to remove the camshaft drive belt and rotate the crankshaft until the marks are aligned.
The crankshaft is rotated to check the coincidence of the marks for the bolt securing the auxiliary drive pulley to it, removing the upper part of the right engine mudguard to access it.
In addition, you can do this in the following ways (especially when adjusting the clearances in the valve drive, when control by marks on the crankshaft pulley is not needed):
Engage any gear (preferably fourth) and slowly roll the car until the marks are aligned;
Engage any gear and hang out one of the front wheels, then turn the hanging wheel until the marks are aligned.
The mark on the camshaft sprocket must align with the mark on the cylinder head cover with the Dacia logo, and the mark on the crankshaft sprocket must align with the mark on the cylinder block.
It becomes visible when the accessory drive pulley is removed.
The notch and round protrusion on the toothed pulley must align with the hole on the cylinder block.
In addition to the marks on the pulleys, the timing belt is marked with paint marks a, which, when setting the valve timing, must also be aligned with the marks on the pulleys.
The process itself
You will need socket wrenches (heads) "for 10" and "for 18".
Remove the right front wheel.
Loosen the wheel bolts only when the vehicle is stationary, on the ground.
If you are working on a pit or overpass, place blocks under the wheels, brake the vehicle with the parking brake and place the front of the vehicle on a secure footing.
Remove the upper part of the right engine mudguard.
Remove the accessory drive belt.
Remove the right powertrain mount.
Remove the five bolts securing the upper timing belt cover.
Remove the lid.
Turn the crankshaft clockwise on the accessory drive pulley bolt until the marks on the camshaft pulley and the cylinder head cover match.
Then loosen the tightness.
Finally remove the pulley mounting bolt.
Remove the pulley.
Remove the three bolts securing the timing belt lower cover.
Remove the lid
Check the alignment of the marks on the camshaft pulley and on the cylinder cover