General information
1 The camshaft is driven by the crankshaft, by means of a timing belt and sprockets. Both sprockets rotate in phase with each other and this provides the correct valve timing as the engine rotates. When the timing belt of Fiat Punto is removed during servicing or repair, it is possible for the camshaft and crankshaft to rotate independently of each other and the correct valve timing is then lost.
2 The design of the engine is such that potentially damaging piston-to-valve contact may occur if the camshaft is rotated when any of the pistons are stationary at, or near, the top of their stroke.
3 For this reason it is important that the correct phasing between the camshaft and crankshaft is preserved whilst the timing belt is off the engine of Fiat Punto. This is achieved by setting the engine in a reference position (known as Top Dead Centre or TDC) before the timing belt is removed and then preventing the camshaft and crankshaft from rotating until the belt is refitted. Similarly, if the engine has been dismantled for overhaul, the engine can be set to TDC during reassembly to ensure that the correct shaft phasing is restored.
4 TDC is the highest point in the cylinder of Fiat Punto that each piston reaches as the crankshaft turns. Each piston reaches TDC at the end of the compression stroke and again at the end of the exhaust stroke. However, for the purpose of timing the engine, TDC refers to the position of No 1 piston at the end of its compression stroke. On all engines in this manual, No 1 piston (and cylinder) is at the timing belt end of the engine Fiat Punto.
5 There are two different procedures for locating TDC on cylinder No 1, and it will be necessary to refer to the engine number to determine which procedure is to be followed. The engine number is stamped on the cylinder block, just below the cylinder head joint at the timing belt end.
8 With the engine number obtained, refer to procedure A or procedure B as follows:
Engine number outside the range 6.800.001 to 7.000.000 - refer to Procedure A
Engine number within the range 6.800.001 to 7.000.000 - refer to Procedure B

Procedure A
7 The camshaft sprocket is equipped with a marking which, when aligned with a reference notch on the cylinder head, indicates that the camshaft is correctly positioned with the piston of cylinder No 1 at TDC on its compression stroke.
8 The crankshaft sprocket is also equipped with a timing mark - when this is aligned with a reference marking on the oil pump cover, the engine is set with the pistons of cylinders No 1 and 4 at TDC. Note that It Is the camshaft positioning that determines whether a piston is on its compression or exhaust stroke.
9 Remove the timing belt upper and lower covers.
10 Remove the spark plugs of Fiat Punto.
11 Turn the engine in its normal direction of rotation (using a socket or spanner on the crankshaft sprocket centre bolt) until pressure can be felt at No 1 cylinder spark plug hole.
12 Continue turning the engine until the camshaft sprocket TDC timing mark is aligned with the notch on the cylinder head and the crankshaft sprocket timing mark is aligned with the mark on the oil pump casing (see illustrations).



Camshaft sprocket and cylinder head TDC timing marks (arrowed) aligned



Crankshaft sprocket and oil pump casing TDC timing marks (arrowed) aligned


13 The engine of Fiat Punto is now set at TDC for No 1 cylinder on compression.

Procedure B
Note: Fiat special tools 1.860.895.000 and 1.870.823.000 (or home-made alternatives) will be required for this procedure.
14 The engines in the range covered by this procedure are not equipped with conventional timing marks and it is therefore necessary to use special tools to determine TDC for No 1 piston, and the correct corresponding position for the camshaft.
15 Remove the timing belt upper and lower covers.
16 Remove the spark plugs.
17 Identify the spark plug HT leads at their ignition coil connections, then disconnect the leads from the two coils. Also disconnect the LT wiring connector from each coil.
18 Undo the retaining bolt, and the upper and lower retaining nuts, and remove the ignition coils, complete with mounting bracket, from the end of the cylinder head of Fiat Punto (see illustrations).



Undo the retaining bolt, and the upper and lower retaining nuts ...



... and remove the ignition coils, complete with mounting bracket


19 Turn the engine of Fiat Punto in its normal direction of rotation (using a socket or spanner on the crankshaft sprocket centre bolt) until pressure can be felt at No 1 cylinder spark plug hole.
20 It is now necessary to set up a dial test Indicator so that the TDC position of No 1 piston can be determined. If Fiat special tool 1.860.895.000 (comprising an adaptor (or the dial test indicator) is available, screw the adaptor into No 1 spark plug hole and mount the gauge on the adaptor. If the Fiat toot is not available, an alternative method is as follows.
21 Mount a conventional dial test indicator in a suitable position (using a piece of scrap metal as a mounting bracket, if necessary) so that the gauge probe is directly above Ho 1 spark plug location. Obtain a length of dowel rod to act as an extension to the gauge probe, and round off one end of the rod with a file.
22 To make a guide for the dowel rod, break off the ceramic upper section of an old spark plug and remove the centre electrode and earth tip. The easiest way to do this is to mount the spark plug in a vice (after removing the ceramic upper section) and drill a hole down through the centre of the plug. The diameter of the drill bit should be the same as the diameter of the dowel rod to be used.
23 Screw the spark plug guide into No 1 spark plug hole of Fiat Punto, then Insert the dowel rod (round end first) through the plug into No 1 cylinder so that It contacts the piston. Move the dial test Indicator into position with its probe contacting the dowel rod (see illustration).



Dial test indicator and probe set up for checking TOC on No 1 piston


24 Turn the engine of Fiat Punto by means of the crankshaft sprocket until the highest reading is shown on the gauge, indicating that No 1 piston is at TOC. Take care when doing this as it is very easy for the dowel rod to jam in its guide.
25 At the other end of the engine, observe the position of the offset slot in the end of the camshaft, visible through the opening normally covered by the ignition coil mounting bracket. The camshaft slot should be horizontal, with the offset below the centreline (see illustration). If this is the case, the engine is now correctly set at TDC for No 1 cylinder on compression.
26 If the camshaft slot offset is above the centreline, remove the dowel rod (to avoid jamming) then turn the crankshaft through one complete revolution, returning No 1 piston to the TDC position as described above.




With No 1 piston at TDC on compression, the camshaft slot should be horizontal, with the offset below the centreline


27 To retain the camshaft in the correct position for all operations entailing removal of the timing belt, Fiat special tool 1.870.823.000, or a suitable alternative must be used. The Fiat tool consists of a metal plate which is secured to the two ignition coil mounting bracket studs on the cylinder head. A flange, welded to the inner face of the tool, engages with the offset slot in the camshaft and retains the camshaft in the set position. A home-made tool can be fabricated from steel strip of the same thickness as the camshaft slot. Bend the strip through 90°, mark and drill a mounting hole, then secure the toot using one of the studs on the cylinder head.