Fiat Uno Manual

Timing chain and sprockets removal and refitting (903 cc engine)
Engine / Timing chain and sprockets removal and refitting (903 cc engine)


1 Remove the alternator drivebelt as described in Chapter 2.

2 Unscrew and remove the crankshaft pulley nut.

3 Disconnect the hoses from the fuel pump.

4 Unbolt and remove the fuel pump with spacer and rod.

5 Support the engine on a hoist or under the sump and disconnect and remove the right-hand mounting. Then unscrew and remove the timing cover bolts. The base of the cover is secured by the front two sump pan studs. Unbolt and lower the front end of the sump. Avoid breaking the gasket. Remove the timing cover.

6 Undo and remove the camshaft sprocket securing bolt; this will also release the fuel pump drive cam from the end of the camshaft.

Note the timing marks on the camshaft and crankshaft sprockets.

7 Using two tyre levers, carefully ease the two sprockets forwards away from the crankcase.

Lift away the two sprockets and timing chain.

8 Remove the Woodruff key from the crankshaft nose with a pair of pliers and note how the channel in the pulley is designed to fit over it. Place the Woodruff key in a container as it is a very small part and can easily become lost. The camshaft sprocket is located on the camshaft by a dowel peg.

Refitting
9 Fit the Woodruff key to the front of the crankshaft.

10 Tap the crankshaft sprocket onto the front of the crankshaft.

11 Turn the sprocket so that the Woodruff key is uppermost.

12 Turn the camshaft until it is in such a position that if the sprocket was fitted the dimple timing mark on the sprocket would be nearest to and in alignment with, the one on the crankshaft sprocket.

13 Engage the timing chain with the teeth of the crankshaft sprocket. Then locate the camshaft sprocket within the upper loop of the chain in such a way that when the sprocket is pushed onto the camshaft, the timing marks will be in alignment. Make sure that the self-tensioning links are on the inside of the chain against the cylinder block (photos).

6.13A Fitting the sprockets and timing chain
6.13A Fitting the sprockets and timing chain

6.13B Timing mark alignment
6.13B Timing mark alignment

6.13C Self-tensioning links on inside of chain
6.13C Self-tensioning links on inside of chain

14 Place the camshaft sprocket onto the camshaft so that its positioning dowel engages.

15 Secure the camshaft sprocket by fitting the special cam, that drives the fuel pump, on its locating dowel. Fit the camshaft sprocket retaining bolt (photo).

6.15 Fitting fuel pump drive cam and sprocket bolt
6.15 Fitting fuel pump drive cam and sprocket bolt

16 Tighten the sprocket bolt to the specified torque.

17 If the timing cover oil seal showed signs of leaking before engine overhaul the old seal should be removed and a new one fitted.

18 Using a screwdriver, carefully remove the old oil seal, working from the rear of the cover.

Fit the new seal making sure it is inserted squarely, and tap home with a hammer.

19 Lubricate the oil seal with engine oil.

20 With all traces of old gasket and jointing compound removed from the timing cover and cylinder block mating faces, smear a little grease onto the timing cover mating face and fit a new gasket in position.

21 Fit the timing cover to the cylinder block and finger tighten the securing bolts, and spring washer. Ensure that the fuel pump pushrod bush is in place in the cover.

22 Wipe the hub of the pulley and carefully place into position on the crankshaft. It should locate on the Woodruff key. It may be necessary to adjust the position of the timing cover slightly in order to centralise the oil seal relative to the pulley hub.

23 Tighten the timing cover securing bolts in a diagonal and progressive manner.

24 Tighten the crankshaft pulley nut to the specified torque again holding the crankshaft against rotation as previously described (paragraph 2) this Section.

25 Refit the fuel pump and alternator drivebelt.

Fig. 1.6 Timing chain and sprockets (Sec 6)
Fig. 1.6 Timing chain and sprockets (Sec 6)

1 Sprocket retaining bolt 2 Fuel pump eccentric cam 3 Timing chain
4 Camshaft sprocket
5 Sprocket locating dowel 6 Camshaft
7 Woodruff key
8 Crankshaft
9 Crankshaft sprocket


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