Adjusting timing and PD element for common rail diesel engine (Articles)

The camshaft of the 1.9L/2.0L 8V TDI PD engine not only actuates the intake and exhaust valves, but also the PD elements (PDE) via roller rocker arms. In the 2.0L 16V PD-TDI engine, the exhaust camshaft actuates the PD elements.

To check the camshaft timing, a diagnostic system such as VCDS is necessary.

An injection is only possible as long as the injection cam transmits force to the pressure distribution element (PDE) with its rising slope.
The shape of the rising flank determines the course of the injection rate during the injection process.
Any adjustment of the camshaft not only shifts the valve timing, but also affects the possible timing window for injection and the fuel delivery rate relative to the crankshaft position.
Similar to a distributor pump that is set too late, a PD-NW (positive displacement nozzle with pressure regulation) that is also set too late can delay the actual start of injection if the target injection starts early (within the Pmax range).
Allerdings wird dann die Einspritzung beim PD-Motor zum normalen Zeitpunkt beendet und somit die Einspritzmenge gegenüber dem Sollwert reduziert, während die VP 37 noch die Sollmenge einspritzt - nur insgesamt zu spät.

Practical experience with an ASZ engine revealed that adjusting the camshaft timing by approximately 3° BTDC (before top dead center) resulted in a more consistent engine performance at high RPMs when accelerating under full throttle. With the factory setting, the engine felt sluggish above approximately 3500 RPM, whereas the adjusted setting allowed for smoother operation in the higher RPM range. The adjusted timing places the crankshaft at the top dead center (TDC) position as indicated by the marking on the transmission flange, as described below.
The effects of a misaligned camshaft are likely to feel similar across all PD engines.
So, if a PD-TDI engine, for example, noticeably loses power somewhere between 3,000 and 4,000 RPM during a full-throttle acceleration in 3rd gear, one should consider the possibility of a "misconfiguration" of the engine control unit, in addition to the usual suspects like the mass airflow sensor and turbocharger issues.

The NW setting can also be used, based on relevant tests, to deliberately influence the motor's performance characteristics (within certain limits).
A slight increase in performance in the higher RPM range appears possible with a more "aggressive" initial setting; further details can be found under.
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The position of the camshaft relative to the crankshaft can be displayed via OBD (e.g., using VCDS), and the corresponding measurement value is called "synchronization angle." For this engine, you can find it in measurement block 4 of the engine control unit.

More information about the synchronization angle:
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The "setting according to guide" method, which reduces performance and uses a timing tool on the crankshaft pulley (instead of the timing mark on the transmission flange), may be intentionally implemented for emissions reasons.
If that is true (unfortunately, verified information is not available), a change to the NOx (nitrogen oxides) setting to improve responsiveness could potentially lead to exceeding emission limits, and therefore, legally speaking, would result in the revocation of the operating permit!

With a little improvisation, it's possible for a DIY enthusiast to adjust and potentially correct the alignment, even without specialized tools.
The installation of the PDE is also relatively straightforward; the most time-consuming part is removing and reinstalling the valve cover.
With these two tools, you essentially have control over the complete mechanical engine adjustment for 1.9 and 2.0 PD engines.

For both tasks, the following minimal equipment is required:
-> A probing tool with a minimum length of 7 cm and a diameter of 6 mm is required; other tools with a smaller diameter can be helpful. The probing tools should be shaped at the "handle end" in such a way that they cannot fall into the lower root canal.
-> Torque wrench and ratchet with sockets 10mm, 13mm, and 18mm, alternatively a ring wrench, a marking pen, and a ruler.
--> 6 mm Allen key.
-> Tool for removing the upper valve cover and, if necessary, for removing interfering intercooler pipes. The openings should then be covered with verschandeln cloths.
-> a flat surface that allows for pushing and pulling the cart forward and backward by at least 1 meter.

To avoid having to turn the engine over with each rotation by pushing the vehicle, it is recommended to rotate the crankshaft using a suitable key. If access to the crankshaft pulley is difficult, the pushing method with two assistants is still recommended.

To check the NW setting of the 1.9/2.0l 8V TDIs, first remove the upper timing chain cover and expose the TDC (Top Dead Center) indicator hole on the engine-transmission flange.
Then, look for a marking "3Z" or "4Z" on the part of the upper timing cover that faces the engine block -> see image 1, where the embossed lettering is highlighted for clarity.
Instead of the 4Z marking, a 3Z marking may be present in the area of the tensioner/bend flange.
In the engine's testing position, which corresponds to Top Dead Center (TDC) of the first cylinder, the notched window on the toothed wheel of the crankshaft is approximately at the 11 o'clock position (Image 2), and one of the Hall sensor marks (two small metal tabs on the engine-side edge of the crankshaft) is aligned with the "Z" mark. The tip of the "Z" mark points towards the center between the metal tabs (Appendix 2, Image 1).

A difference between a factory-set or workshop-adjusted timing and this procedure may arise because, when disconnecting the timing chain using a "crankshaft lock," the crankshaft may not be precisely at the top dead center (TDC) position as indicated by the flywheel mark, but rather slightly past TDC, approximately the 3° crankshaft degrees mentioned earlier.
This difference between the crankshaft position sensor's reference point and the top dead center (TDC) mark during engine control unit (ECU) calibration (NW gear) results in the aforementioned differences in the engine's performance characteristics.
To install the crankshaft pulley, the timing wheel/damper must be unscrewed from the crankshaft, and the lower timing belt cover must be removed.

To check the NW setting, rotate the engine from a forward rotation to the TDC (Top Dead Center) of the first cylinder. The NW should then be in the described test position, and ideally, the 6 mm spacer tool can be fully inserted, i.e., 6 cm deep (Appendix 2, Figure 2).
If that's not the case, you can try using thinner probing tools to see if the cable is at least close to the intended position.

Note: Behind the clearly visible, elongated slot in the outer part of the NW wheel, there is the actual 6mm circular hole in the inner part of the NW wheel.
Only if the drill aligns perfectly with the locating hole in the cylinder head can the locating tool be fully inserted; otherwise, it will hit the side of the cylinder head!

Attention: If the timing mark was set based on a reverse rotation, the normal tension of the timing belt is no longer correct, and the crankshaft (even with the timing mark set correctly!) is more or less before top dead center, which results in what appears to be an "too early" timing mark setting.

If the 6mm setting tool for the cable duct (or when the cable duct is already installed) cannot be easily inserted, the setting is incorrect. To correct this, the toothed part and the inner part of the cable duct setting wheel must be rotated relative to each other.
To do this, the three clamping screws need to be loosened by approximately half a turn.

Attention:
When tightening the three clamping screws after adjustment, the torque of 25 Nm should be strictly adhered to with a cold engine (2.0l 16V TDI: 30 Nm).
If you don't have a torque wrench available, you should mark the position of the screws before loosening them, for example, by drawing a line with a ruler across the screw head, pointing directly to the center of the central screw. When tightening the clamping screws completely, turn them until the lines again point to the center of the central screw.

Once the clamping screws are loosened, use the longest possible open-end wrench (18 mm) on the central screw on the northwest side and rotate the inner part to the indexing position, so that the 6 mm tool can be easily inserted completely.
The fear of loosening or overtightening the central screw when turning the nut is usually unfounded: Up to the beginning of the tightening torque range of the central screw (100 Nm), nothing harmful can happen. You can turn the nut using a torque wrench, for example, with a setting of 70 Nm.
Make sure the centering tool is fully inserted, tighten the clamping screws, remove the centering tool (!!), and rotate the motor at least one full revolution in the counter-clockwise direction.
Then, adjust the setting as described, starting from the forward rotation of the motor, and if necessary, make further corrections.

Since the interpretation of the adjustment and correction direction is not immediately obvious, you can refer to the following scheme:
Tightening the set screws in the elongated holes of the gear clockwise = later adjustment of the end play.
Turning the set screws in the elongated holes of the gear clockwise = previous NW (neutral width) setting.

However, for example, the presence of set screws in the right half of the elongated holes does not necessarily mean that the neutral position (NW) is actually set "early."
If the timing belt was installed in such a way that the crankshaft's camshaft sprocket is one tooth "behind," then the clamping screws used for adjustment will need to be almost at the early limit of the elongated holes, even when the camshaft is correctly aligned.

To adjust the "preload" of the PDE , first remove the upper cylinder head cover and the valve cover.
On the ASZ engine in the Polo 9N, the cover would catch on the intake manifold flange and the EGR unit by approximately 2mm when being removed.
"Quite right," one would probably have needed to unscrew the intake manifold, but a few strokes with the file on both parts also solved the problem.

The positive displacement (PD) pumps are adjusted to a defined distance from the pump piston to the bottom of the high-pressure chamber, setting them at their "lower dead center" position.
Therefore, the pressure drop equipment (PDE) must first be precisely positioned at the lowest dead point (end point of the lifting stroke).
The workshop is using a specialized holder to mount a dial gauge on the central axis for UT (ultrasonic testing) measurements.
The lower dead center, which is the maximum deflection of the rocker arm, can also be determined in a different way by attaching a long "pointer" to the rocker arm. For example, you could place a 18mm ring wrench on the lock nut, insert a long (or extended) Allen wrench into the adjustment screw, attach a wire to the rocker arm, etc. (see Appendix 2, Image 3).

Then, the motor is rotated until the pointer is at its maximum forward position (when installed horizontally) or downward position.

Achtung: Erfolgt die Einstellung nicht im Endpunkt des Förderhubes, dann wird beim nächsten Motorlauf der Förderkolben auf den Boden des PDE-Hochdruckraumes knallen, worauf das schwächste Glied der Kraftübertragungskette zwischen Kurbelwelle und PDE kapitulieren wird. Ob sich das nun z.B. als Zahnriemenriß oder Kipphebelbruch äußert, oder die Kipphebelwelle aus dem Zylinderkopf gerissen wird, darüber sind hier noch keine Informationen bekannt. In In any case, the damage would be very expensive, which is why one should exercise the appropriate care.

Before loosening the lock nuts of the PDE adjustment screws, it's important to check if a torque wrench is available for re-tightening. If not, first mark the position of the nuts on the pivot lever.

Loosen the lock nut on the activated pressure distribution element (PDE) and screw the adjustment screw into the rocker lever until you feel a distinct resistance: the PDE is now at its lower limit.
From this position, turn the adjustment screw counterclockwise by 225° (half a turn plus one-eighth of a turn). Tighten the lock nut to 30 Nm or until the marking is reached (Appendix 2, Figure 4).
(More recent VAG instructions state that the adjustment screw should only be turned out by 180°, instead of 225°. This applies to all PD engines, even if a previous adjustment value of 225° was specified for the same engine. The reasons for this change are not known here.)

That's it for the first PDE. Now, repeat the entire exercise for the remaining PDEs.

Before reassembling the valve cover, it's advisable to apply a permanent sealant around the area of the two water pump mounting brackets. This is because the PD (distributorless) engines tend to have slight oil leaks in this area, which should be avoided, especially in the vicinity of the timing belt.

Then install the valve cover and timing belt cover, and during a test drive, check to ensure that the valve cover gasket is truly sealed.