| VELOSTER(FS) >2012 > G 1.6 GDI > Engine Mechanical System > General Information>Repair procedures |

Compession Pressure Inspection
If the there is lack of power, excessive oil consumption or poor fuel economy, measure the compression pressure.
1. | Make sure the oil in the crankcase is of the correct viscosity and at the correct level and that the battery is correctly charged. Operate the vehicle until the engine is at normal operating temperature. Turn the ignition switch to the OFF position.
2. | Remove the engine cover.
3. | Disconnect the injector extension connector (A) and the ignition coil connectors (B).
4. | Remove the ignition coils (A).
5. | Remove the spark plugs. Using a 16mm plug wrench, remove the 4 spark plugs.
6. | Check the cylinder compression pressure.
(1) | Insert a compression gauge into the spark plug hole.
(2) | Set the throttle plate in the wide-open position.
(3) | While cranking the engine, measure the compression pressure.
Always use a fully charged battery to obtain engine speed of 250rpm or more.
(4) | Repeat step 1) through 3) for each cylinder.
This measurement must be done in as short time as possible.
Compression pressure Standard : 1225.83kPa (12.5kg/cm², 177.79psi) (200~250 rpm) Minimum : 1078.73kPa (11.0kg/cm², 156.46psi) Difference between each cylinder : 98kPa (1.0kg/cm², 14psi) or less
(5) | If the cylinder compression in one or more cylinders is low, pour a small amount of engine oil into the cylinder through the spark plug hole and repeat step 1) through 3) for cylinders with low compression.
A. | If adding oil helps the compression, it is likely that the piston rings and/or cylinder bore are worn or damaged.
B. | If pressure stays low, a valve may be sticking or seating is improper, or there may be leakage past the gasket.
7. | Install the spark plugs.
Tightening torque : 7.8 ~ 9.8N.m (0.8 ~ 1.0kgf.m, 5.8 ~ 7.2lb-ft)
8. | Install the ignition coil (A).
Tightening torque : 9.8 ~ 11.8 N.m (1.0 ~ 1.2 kgf.m, 7.2 ~ 8.7 lb-ft)
9. | Connect the injector extension connector and the ignition coil connectors.
10. | Install the engine cover.
Valve Clearance Inspection And Adjustment
Inspect and adjust the valve clearance when the engine is cold (Engine coolant temperature : 20°C) and cylinder head is installed on the cylinder block.
1. | Remove the cylinder head cover. (Refer to Timing system)
2. | Set No.1 cylinder to TDC/compression.
(1) | Turn the crankshaft pulley and align its groove with the timing mark of the timing chain cover.
(2) | Check that the marks of the intake and exhaust CVVT sprockets are in straight line on the cylinder head surface as shown in the illustration. If not, turn the crankshaft one revolution (360°).
3. | Inspect the valve clearance.
(1) | Check only the intake valves of the 1st and 2nd cylinders and exhaust valves of the 1st and 3rd cylinders for their clearance.
A. | Using a thickness gauge, measure the clearance between the tappet and the base circle of camshaft.
B. | Record the out-of-specification valve clearance measurements. They will be used later to determine the required tappet for adjusting.
Valve clearance specification (Engine coolant temperature : 20°C [68°F]) Limit Intake : 0.17 ~ 0.23mm (0.0067 ~ 0.0091in.) Exhaust : 0.22 ~ 0.28mm (0.0087 ~ 0.0110in.)
(2) | Turn the crankshaft pulley one revolution (clockwise 360°) and align its groove with timing mark of the timing chain cover.
(3) | Check the intake valves of the 3rd and 4th cylinders and exhaust valves of the 2nd and 4th cylinders for their clearance.
4. | Adjust the intake and exhaust valve clearance.
(1) | Set the No.1 cylinder to the TDC/compression position.
(2) | Remove the timing chain. (Refer to Timing system)
Put paint marks on the timing chain links (2 places) that meet with the timing marks of the intake and exhaust CVVT sprockets.
(3) | Remove the camshaft bearing caps (A) with the order below.
(4) | Remove the intake camshaft assembly.
(5) | Remove the exhaust camshaft assembly.
(6) | Measure the thickness of the removed tappet using a micrometer.
(7) | Calculate the thickness of a new tappet so that the valve clearance comes within the specificified value.
Valve clearance (Engine coolant temperature : 20°C) T : Thickness of removed tappet A : Measured valve clearance N : Thickness of new tappet Intake : N = T + [A - 0.20mm(0.0079in.)] Exhaust : N = T + [A - 0.25mm (0.0098in.)]
(8) | Select a new tappet with a thickness as close as possible to the caculated value.
Shims are available in 41 size increments of 0.015mm (0.0006in.) from 3.00mm (0.118in.) to 3.690mm (0.1417in.)
(9) | Place a new tappet on the cylinder head.
(10) | Install the exhaust camshaft assembly.
(11) | Install the intake camshaft assembly.
(12) | Install the camshaft bearing caps with the order below.
Tightening torque : 1st step M6 bolt : 5.9 N.m (0.6 kgf.m, 4.3 lb-ft) M8 bolt : 9.8 N.m (1.0 kgf.m, 7.2 lb-ft) 2nd step M6 bolts : 11.8 ~ 13.7N.m (1.2 ~ 1.4kgf.m, 8.7 ~ 10.1lb-ft) M8 bolts : 18.6 ~ 22.6N.m (1.9 ~ 2.3kgf.m, 13.7 ~ 16.6lb-ft)
(13) | Install the timing chain. (Refer to Timing system)
(14) | Turn the crankshaft two turns in the operating direction(clockwise) and check that the marks of the intake and exhaust CVVT sprockets are in straight line on the cylinder head surface.
(15) | Recheck the valve clearance.
Valve clearance (Engine coolant temperature : 20°C) [Specification] Intake : 0.17 ~ 0.23mm (0.0067 ~ 0.0091in.) Exhaust : 0.22 ~ 0.28mm (0.0087 ~ 0.0110in.)