Checking and Adjusting the TDI 1.9L Injector Pump (Articles)

Last edited on 03-02-2023, 23:56, edited 9 times in total.

Inspect and Adjust the 1.9 Liter TDI-Injector Pump
TDI Einspritzpumpe

Depending on the available equipment, there are two ways to check for the correct injection start.
My thanks go to Ulf for the part of the adjustment using DIY tools.

Setting with VCDS diagnostic system and the TDI timing checker:

To do this, start the engine and first select the function Basic Settings / Grundeinstellung' (VCDS must be licensed/activated) on the diagnostic tool, and then Display group 000

"This is because only during this function is the spray adjuster constantly controlled and reaches its maximum late-actuation position."
Then, in the 000 measurement group, you read the values for fields 2 (injection timing) and 9 (fuel temperature) and compare them with the following diagram:

The engine should be at its operating temperature, the crucial factor is the fuel temperature in the fuel pump, which is adjusted during the process.

should be between 20°C and 60°C.

Es bietet sich der Gebrauch des 'TDI-Timing-Checkers' an, der die passenden Diagramme für alle entsprechenden Motoren gleich mitbringt. Es ist nur der entsprechende Motorkennbuchstabe auszuwählen und das jeweils zur Einstellung passende Diagramm wird eingeblendet:

Die Kraftstofftemperatur sollte bei der Einstellung relativ hoch liegen, um zeitaufwendige Wartezeiten zu verringern kann im TDI-Timing-Checker die Mindesttemperatur ignoriert werden (dazugehörige Checkbox klicken).

Hat man kein Diagramm für seinen Motor, kann man sich behelfen indem man im Fahrbetrieb das Taktverhältnis des Spritzverstellers ansieht (normaler Modus, Meßwertblock 4, Feld 4). Hier sollten noch Reserven zum minimalem und maximalem Endwert vorhanden sein.
Um den statischen Einspritzzeitpunkt anzupassen, verstellt man entweder über das Pumpenrad oder die Pumpenbefestigung bis man im Diagramm den gewünschten Wert erreicht.To do this, follow the instructions below.

Before explaining the method, a brief description of the spray adjustment function.

The VP 37 fuel pump, like the older, purely mechanical Bosch distributor pumps, has a hydraulic starting adjustment that causes an early starting adjustment that increases with engine speed. This is (primarily for adjusting to the current injection amount) reduced by the engine computer until the starting point detected by the needle position sensor matches the target value according to the map. He controls an electric valve (fuel metering valve) that diverts a portion of the fuel from the hydraulic pre-metering system.

Without backpressure, the nozzle adjuster remains closed, and therefore the hydraulic pre-adjustment is fully effective, which is approximately equivalent to full-load operation. As the backpressure increases, the nozzle adjuster opens further and further, thereby reducing the pre-adjustment even more. This applies under partial load or when idling.

To control the spray regulator, the engine computer switches the full power supply on and off in rapid succession and with varying time intervals ("duty cycle"), resulting in effective voltages between just above zero and approximately 13 volts.
At a target resistance of 12 - 20 Ohms, the maximum spray adjuster current is in the order of 1 Ampere.

The active adjustment range of the pump (with the default setting as the starting point) is only slightly larger than the difference between the earliest and latest target spray start values according to the characteristic curve.
This means that even with slight miscalibration, either the maximum advance or retard timing according to the baseline setting will no longer be achieved.
The same can happen if the desired injection start timing is shifted using software adaptation (VCDS) without corresponding adjustment of the baseline setting.
In such cases, the injection start control can operate at either the advance or retard setting, i.e., the fuel injector actuator will regularly have an effective voltage of almost zero (at full load) or 13 volts (in partial load range), even with an incorrect pump setting.

If the fuel injection pressure fluctuates within these values during operation, the pump is correctly adjusted and the fuel injection system is fully functional. Therefore, measuring the spray adjuster voltage allows for a relatively accurate assessment of the pump setting.

To measure the voltage, you need to connect the two wires to the fuel injector control and observe the voltage as accurately as possible using an analog meter (which, due to its inertia, displays the effective average of the pulsed voltage) while driving the vehicle.

A constant, slight fluctuation in the fuel injector adjustment voltage indicates normal operation. In partial load conditions, the voltage responds sensitively and continuously to all gas pedal movements (more gas = lower voltage and vice versa); jumps are only noticeable when the pedal is completely released and then re-depressed (throttle closure). Otherwise, a fluctuating voltage indicates a faulty fuel injector position sensor, a stuck fuel injector, or Adjustable hydraulics, cable breaks, or other issues.

If the fuel pump adjustment is incorrect (i.e., the fuel injector voltage often reaches a limit), you only need to "adjust" in the direction of the more frequent adjustment points: If the early-stop (below approximately 0.5 volts) is already reached in the partial load range, you set the pump to start fueling earlier, and vice versa.

If the control repeatedly drifts to the early or late position even after multiple pump adjustments, it is recommended to set the pump for optimal performance, good starting behavior, and minimal fuel consumption, specifically when accelerating fully in the 2nd or 3rd gear. If a spray adjuster voltage of approximately 0.8 to 1.2 volts is achieved,
then the control is already in the middle load range at the end of the stroke, the hydraulic and/or electrical adjustment range is limited by deposits in the pump or other defects.

Such problems remain undetected due to the default settings, because here, the pump is only adjusted to the correct (late) start of injection in idle mode. If the adjustment range is insufficient, the required early adjustment is no longer achieved under high load - the engine becomes sluggish and thirsty, but the cause is often sought elsewhere, as long as there is no clear error code found or the control behavior is checked during a test drive (e.g. Datalogging with VCDS and checking with KDataScope).

Depending on the engine or fuel pump, you now have
two options, either to rotate the pump or the timing belt pulley on the pump shaft.
If you have a motor where the adjustment is made via the pump gear, it is important to note that the mounting screws are tension screws that must be replaced after use (torque 20Nm + 90°).
Therefore, the screws should only be tightened to 20Nm for checking purposes and then turned another 90° once the correct setting has been achieved.

The central nut on the pump gear is not to be loosened.
When there is frequent late-onset in the partial load range and/or a full-load voltage of approximately 2 volts, the pump adjustment should be adjusted towards "late".

To conceal the pump using the pump mounting remove the upper timing belt cover and loosen the 3 timing belt-side fixing screws and one screw at the other end of the pump so that the pump can just turn. When fixing, first tighten the timing belt-side screws to prevent the pump from derailing in the console due to the wear-promoting timing belt sliding. Finally, loosen and re-tighten all pump-side fittings of the fuel lines to prevent vibrations caused by voltage.
Since even a slight displacement of the pump by 1 millimeter causes noticeable voltage fluctuations, the initial position must definitely be marked.

In case of emergency, the pump can be adjusted so that it operates at the late-engagement point of the engine's fuel injector adjustment, even when the vehicle is stationary. After this, it is important to check and, if necessary, correct the pump adjustment as described on a test drive.

Checking and Adjusting the TDI 1.9L Injector Pump
dieselschrauber 23-06-2003, 15:58
Inspect and Adjust the 1.9 Liter TDI-Injector Pump After replacing the timing belt, the starting point of the fuel pump should be re-adjusted. Depending on the available equipment, there are two ways to check for the correct injection start. My thanks go to Ulf for the part of the adjustment using DIY tools. Setting with VCDS diagnostic system and the TDI timing checker: To do this, start the engine and first select the function Basic Settings / Grundeinstellung' (VCDS must be licensed/activated) on the diagnostic tool, and then Display group 000 "This is because only during this function is the spray adjuster constantly controlled and reaches its maximum late-actuation position." Then, in the 000 measurement group, you read the values for fields 2 (injection timing) and 9 (fuel temperature) and compare them with the following diagram: The engine should be at its operating temperature, the crucial factor is the fuel temperature in the fuel pump, which is adjusted during the process. should be between 20°C and 60°C. Es bietet sich der Gebrauch des 'TDI-Timing-Checkers' an, der die passenden Diagramme für alle entsprechenden Motoren gleich mitbringt. Es ist nur der entsprechende Motorkennbuchstabe auszuwählen und das jeweils zur Einstellung passende Diagramm wird eingeblendet: Die Kraftstofftemperatur sollte bei der Einstellung relativ hoch liegen, um zeitaufwendige Wartezeiten zu verringern kann im TDI-Timing-Checker die Mindesttemperatur ignoriert werden (dazugehörige Checkbox klicken). Hat man kein Diagramm für seinen Motor, kann man sich behelfen indem man im Fahrbetrieb das Taktverhältnis des Spritzverstellers ansieht (normaler Modus, Meßwertblock 4, Feld 4). Hier sollten noch Reserven zum minimalem und maximalem Endwert vorhanden sein. Um den statischen Einspritzzeitpunkt anzupassen, verstellt man entweder über das Pumpenrad oder die Pumpenbefestigung bis man im Diagramm den gewünschten Wert erreicht.To do this, follow the instructions below. Approach with DIY tools: Before explaining the method, a brief description of the spray adjustment function. The VP 37 fuel pump, like the older, purely mechanical Bosch distributor pumps, has a hydraulic starting adjustment that causes an early starting adjustment that increases with engine speed. This is (primarily for adjusting to the current injection amount) reduced by the engine computer until the starting point detected by the needle position sensor matches the target value according to the map. He controls an electric valve (fuel metering valve) that diverts a portion of the fuel from the hydraulic pre-metering system. Without backpressure, the nozzle adjuster remains closed, and therefore the hydraulic pre-adjustment is fully effective, which is approximately equivalent to full-load operation. As the backpressure increases, the nozzle adjuster opens further and further, thereby reducing the pre-adjustment even more. This applies under partial load or when idling. To control the spray regulator, the engine computer switches the full power supply on and off in rapid succession and with varying time intervals ("duty cycle"), resulting in effective voltages between just above zero and approximately 13 volts. At a target resistance of 12 - 20 Ohms, the maximum spray adjuster current is in the order of 1 Ampere. The active adjustment range of the pump (with the default setting as the starting point) is only slightly larger than the difference between the earliest and latest target spray start values according to the characteristic curve. This means that even with slight miscalibration, either the maximum advance or retard timing according to the baseline setting will no longer be achieved. The same can happen if the desired injection start timing is shifted using software adaptation (VCDS) without corresponding adjustment of the baseline setting. In such cases, the injection start control can operate at either the advance or retard setting, i.e., the fuel injector actuator will regularly have an effective voltage of almost zero (at full load) or 13 volts (in partial load range), even with an incorrect pump setting. If the fuel injection pressure fluctuates within these values during operation, the pump is correctly adjusted and the fuel injection system is fully functional. Therefore, measuring the spray adjuster voltage allows for a relatively accurate assessment of the pump setting. To measure the voltage, you need to connect the two wires to the fuel injector control and observe the voltage as accurately as possible using an analog meter (which, due to its inertia, displays the effective average of the pulsed voltage) while driving the vehicle. A constant, slight fluctuation in the fuel injector adjustment voltage indicates normal operation. In partial load conditions, the voltage responds sensitively and continuously to all gas pedal movements (more gas = lower voltage and vice versa); jumps are only noticeable when the pedal is completely released and then re-depressed (throttle closure). Otherwise, a fluctuating voltage indicates a faulty fuel injector position sensor, a stuck fuel injector, or Adjustable hydraulics, cable breaks, or other issues. If the fuel pump adjustment is incorrect (i.e., the fuel injector voltage often reaches a limit), you only need to "adjust" in the direction of the more frequent adjustment points: If the early-stop (below approximately 0.5 volts) is already reached in the partial load range, you set the pump to start fueling earlier, and vice versa. If the control repeatedly drifts to the early or late position even after multiple pump adjustments, it is recommended to set the pump for optimal performance, good starting behavior, and minimal fuel consumption, specifically when accelerating fully in the 2nd or 3rd gear. If a spray adjuster voltage of approximately 0.8 to 1.2 volts is achieved, then the control is already in the middle load range at the end of the stroke, the hydraulic and/or electrical adjustment range is limited by deposits in the pump or other defects. Such problems remain undetected due to the default settings, because here, the pump is only adjusted to the correct (late) start of injection in idle mode. If the adjustment range is insufficient, the required early adjustment is no longer achieved under high load - the engine becomes sluggish and thirsty, but the cause is often sought elsewhere, as long as there is no clear error code found or the control behavior is checked during a test drive (e.g. Datalogging with VCDS and checking with KDataScope). Depending on the engine or fuel pump, you now have two options, either to rotate the pump or the timing belt pulley on the pump shaft. If you have a motor where the adjustment is made via the pump gear, it is important to note that the mounting screws are tension screws that must be replaced after use (torque 20Nm + 90°). Therefore, the screws should only be tightened to 20Nm for checking purposes and then turned another 90° once the correct setting has been achieved. The central nut on the pump gear is not to be loosened. When there is frequent late-onset in the partial load range and/or a full-load voltage of approximately 2 volts, the pump adjustment should be adjusted towards "late". To conceal the pump using the pump mounting remove the upper timing belt cover and loosen the 3 timing belt-side fixing screws and one screw at the other end of the pump so that the pump can just turn. When fixing, first tighten the timing belt-side screws to prevent the pump from derailing in the console due to the wear-promoting timing belt sliding. Finally, loosen and re-tighten all pump-side fittings of the fuel lines to prevent vibrations caused by voltage. Since even a slight displacement of the pump by 1 millimeter causes noticeable voltage fluctuations, the initial position must definitely be marked. In case of emergency, the pump can be adjusted so that it operates at the late-engagement point of the engine's fuel injector adjustment, even when the vehicle is stationary. After this, it is important to check and, if necessary, correct the pump adjustment as described on a test drive. Last edited on 03-02-2023, 23:56, edited 9 times in total.

Back to top