General information
1. The sprockets of the camshaft, crankshaft, injection pump and auxiliary shaft are driven by a toothed belt and rotate in phase.
2. The design of the engines discussed in this chapter. is such that when the timing belt is removed, when the crankshaft rotates, the pistons rest against the valves. Therefore, it is important to observe the relative positions of the crankshaft, camshaft and (if provided) auxiliary shaft with the timing belt removed. This is achieved by setting the motor to a certain position (called TDC - top dead center) before removing the timing belt and preventing the shafts from turning. For the same purpose, when repairing an engine, the engine must be installed at TDC, restoring the correct phasing of the shafts.
3. TDC - the highest point that the piston of the corresponding cylinder reaches (in a four-stroke engine twice per cycle; one cut on the compression stroke and the other on the exhaust stroke). Usually (unless otherwise stated) this implies the TDC of the first cylinder in the compression stroke. Cylinders are numbered 1 to 4 starting from the timing belt.
Installing piston No. 1 at TDC
4. Remove the valve cover and accessory belts as described in paragraphs 7 and 6 respectively. Remove the outer timing belt cover as described in paragraph 4. Remove the glow plugs as described in chapter 5B to make it easier to turn the engine.
5. If provided, remove the plug to control the mark in the gearbox bell, using, if necessary, a nut or bolt head (pic. 2.5, a, b). Turn the crankshaft clockwise with a knob until the TDC marks on the flywheel / faceplate are aligned with the pointer in the hole on the bell and the hole on the injection pump sprocket with the hole on its mounting bracket.
Note: On the ANN engine, the cutout on the inside of the sprocket must be aligned with the hole in the bracket.
6. To lock the engine in this position, you need to fix the camshaft (not his star) and the TN8D sprocket in the appropriate positions using special fixing tools, you can make a homemade tool, but for accuracy, it is strongly recommended that you purchase a branded tool from an Audi / VAG dealer (pic. 2.6).
7. Align the protrusion of the fixing bar with the slot in the heel of the camshaft (pic 2.7).
8. After installing the fixing bar in the groove of the camshaft, gently turn it slightly (turning the crankshaft clockwise) so that the locking bar rests on the surface of the cylinder head. Measure the gap between the opposite end of the bar and the head surface using a set of feeler gauges.
9. Unscrew the camshaft carefully back, pull out the dipstick. A further development of the idea is to install two probes of the same thickness, equal to half the measured gap, on both sides of the fixing bar between it and the cylinder head. So the camshaft will be set to the position corresponding to the TDC of the compression stroke of the first cylinder (pic. 2.9).
10. Insert the fixing pin into the mounting holes (or cutout) injection pump sprocket and its mounting bracket. In this way, the pump will be set to the position corresponding to the TDC of the compression stroke of the first cylinder (pic. 2.10, a, b).
11. Now the engine is set to TDC on the compression stroke of the first cylinder.
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