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 controls the intake and exhaust valves, but also actuates the common rail injectors (PDEs) via roller rocker arms. In the 2.0L 16V PD-TDI engine, the exhaust camshaft actuates the common rail injectors.

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.
Adjusting the camshaft therefore not only shifts the valve timing but also affects the possible injection timing window and the fuel delivery rate relative to the crankshaft position.
Similar to a distributor pump that is set too late, a positive displacement (PD) nozzle with a delayed setting can delay the actual start of injection if the target injection starts early (within the Pmax range).
However, in the case of a PD engine, the injection is then terminated at the normal time, thus reducing the amount of fuel injected compared to the target value, while the VP 37 continues to inject the target amount – but overall, too late.

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 and smoother acceleration at high RPMs when accelerating under full throttle. With the factory setting, the engine felt sluggish above approximately 3500 rpm. The adjusted timing places the crankshaft according to the marking on the transmission flange, indicating top dead center.
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 between 3,000 and 4,000 RPM during full acceleration in 3rd gear, one should consider the possibility of an "incorrect setting" of the engine control unit, in addition to common issues like the mass airflow sensor or turbocharger problems.

The Northwest (NW) setting can also be used, based on relevant experiments, to deliberately influence the motor's performance characteristics (within certain limits).
A slight increase in performance at higher RPMs seems possible with a more aggressively "early" setting; further details can be found under.
https://community.dieselschrauber.org/en/viewtopic.php?t=6847

The position of the camshaft relative to the crankshaft can be displayed via OBD (e.g., using VCDS), and the corresponding value is called the "synchronization angle." For this engine, you can find it in measurement block 4 of the engine control unit.

More information about the synchronization angle:
https://community.dieselschrauber.org/en/viewtopic.php?t=14944

The performance-reducing "setting according to guide" using a marking tool on the crankshaft pulley (instead of using the TDC mark on the transmission flange) may be intentional for emissions reasons.
If that is true (unfortunately, verified information is not available), a change to the NOx setting in order 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 the DIY enthusiast to check and potentially adjust the settings without needing any exotic or 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 can practically control the entire mechanical engine adjustment on 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 smaller diameters can be helpful. The probing tools should be shaped at the "handle" end to prevent them from falling into the lower cable channel.
-> Torque wrench and ratchet with sockets (10mm, 13mm, and 18mm), alternatively a set of open-end wrenches, a marking pen, and a ruler.
--> Hex key 6 mm.
-> Tool for removing the upper high-voltage cover and, if necessary, for dismantling interfering intercooler pipes. The openings should then be covered with verschandeln cloths.
-> a flat surface that allows for pushing and pulling the cart back and forth over a distance of at least 1 meter.

To avoid having to push the vehicle for every engine rotation, it is recommended to turn the crankshaft using a suitable key. If access to the crankshaft pulley is difficult, the pushing method with two assistants is still an option.

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) alignment 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 cylinder 1, the notched window on the timing gear is located 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 pulley) aligns with the "Z" mark. The tip of the "Z" mark points towards the center between the two metal tabs (Appendix 2, Image 1).

A difference between the factory/workshop procedure and this guide may arise because, when disconnecting the crankshaft using a "crankshaft stop" at the timing wheel, the crankshaft position (KW) might not be exactly at the top dead center (TDC) position as indicated by the flywheel mark, but slightly after TDC, approximately the 3° KW mentioned earlier.
This difference between the position determined by the crankshaft stop and the TDC mark during engine control calibration (camshaft gear) results in the aforementioned differences in the motor's performance characteristics.
To install the crankshaft lock, you must remove the pulley/damper from the crankshaft and disassemble the lower timing cover.

To check the camshaft timing, rotate the engine from a forward rotation to the top dead center (TDC) of the first cylinder. The camshaft should then be in the described test position, and ideally, the 6 mm spacer tool can be inserted completely, i.e., 6 cm deep (Appendix 2, Figure 2).
If not, you can try using thinner probing tools to see if the cable is at least close to its intended position.

Note: Behind the clearly visible, long slot in the outer part of the northwest wheel is the actual 6mm round hole used for alignment, located in the inner part of the northwest wheel.
Only if the drill aligns perfectly with the locating hole in the cylinder head can the aligning tool be fully inserted; otherwise, it will hit the side of the cylinder head.

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

If the 6mm setting tool for the cable duct (or when the cable duct is already in place) cannot be easily inserted, then the adjustment is incorrect. To correct this, the tooth section and inner part of the cable duct 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 that points exactly to the center of the central bolt. When tightening the clamping screws completely, turn them until the lines again point to the center of the central bolt.

Once the clamping screws are loosened, use the longest possible wrench (18 mm) to engage the central screw on the northwest side and rotate the inner part into the indexing position, ensuring that the 6 mm tool can be easily inserted completely.
The fear of loosening or overtightening the central screw when turning the nozzle 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 nozzle 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 negative direction.
Then, adjust the setting as described while monitoring it from the motor's forward rotation, 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.
Tighten the set screws in the elongated holes of the gear clockwise = previous counterclockwise (NW) 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 chain was installed in such a way that the camshaft sprocket is one tooth "behind" the crankshaft sprocket, then the clamping screws used for adjustment will have to be almost at the early limit of their 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 catches on approximately 2mm when removing it, specifically on the screw flange of the intake manifold and the EGR unit.
"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 pressure differential (PDE) is set to a defined distance from the pump piston to the bottom of the high-pressure chamber, specifically at the "lower dead center" position.
Therefore, the pipeline equipment that needs to be installed must first be precisely positioned at the lowest dead point (the end of the lifting stroke).
The workshop is mounting a dial gauge using a special holder on the central axis (ZK) to check the UT (undulating tool).
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 an 18mm wrench on the lock nut, insert a long (or extended) Allen key into the adjustment screw, attach a wire to the rocker arm, or something similar (see Appendix 2, Image 3).

Then the motor is rotated until the pointer deflects as far forward as possible (when installed horizontally) or downward.

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 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 rocker arm.

Loosen the lock nut on the actuated pressure distribution element (PDE) and screw the adjustment screw into the tilting lever as far as you can until you feel a distinct resistance: this indicates that the PDE is at its lower limit.
From this position, turn the adjustment screw counterclockwise by 225° (half a rotation plus one-eighth of a rotation). Tighten the lock nut to 30 Nm or until it reaches the marking (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 this exercise with 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 near the timing belt.

Then install the valve cover and timing belt tensioner, and during a test drive, check whether the valve cover gasket is truly sealed.