The process of adjusting injection pump timing on a TDI engine, specifically the ALH engine, requires careful mechanical adjustment using VCDS (Vag-Com Diagnostic System) as a guide. This guide outlines the steps to properly adjust the timing using the “hammer mode” in VCDS when adjusting the pump sprocket position alone isn’t sufficient. This method is used when the timing is significantly off and needs to be brought into the proper range before finer adjustments can be made.
Using VCDS to Guide Mechanical Timing Adjustment
Before beginning, ensure your engine is at operating temperature and you have a genuine Ross-Tech cable or licensed VCDS-Lite software.
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Engine Measuring Blocks: Connect VCDS to your vehicle’s OBD-II port. Select (1) Engine, then (8) Measuring Blocks. Navigate to group 000. (You might need to scroll up past the highest group number to reach 000).
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Basic Settings: Enter Basic Settings mode. This disables any computer-controlled timing adjustments and activates the flashing glow plug indicator light on your dashboard.
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TDI Timing Graph: Select “TDI-Timing.” This displays a graph indicating your engine’s current mechanical timing. The graph will show whether your timing is advanced or retarded relative to the ideal setting.
Mechanical Adjustment Procedure
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Prepare for Adjustment: With the engine off, locate the three bolts securing the pump sprocket to the injection pump hub. Before loosening these bolts, place a 22mm box-end wrench on the large central nut of the pump hub. This nut maintains pre-load on the injection pump. Loosen the three 13mm bolts slightly, but do not fully remove them. Keeping tension on the central nut with the wrench prevents the pump hub from moving abruptly when the final bolt is loosened.
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Adjust Timing: With the three bolts slightly loose and the 22mm wrench on the central nut, gently turn the central nut to adjust the timing. Turning the wrench clockwise (towards the front of the car) advances the timing, while turning counter-clockwise (towards the rear) retards it. Crucially, only adjust the nut in small increments (maximum 1/4 inch wrench movement at a time). Large adjustments can prevent the engine from starting.
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Verify Adjustment: Tighten the three 13mm bolts securely. Start the engine and reconnect VCDS. Repeat steps 1-3 to check the timing graph. This process may require several iterations (up to 5 attempts) to achieve the desired timing.
Fine-Tuning and Considerations
This mechanical adjustment method using VCDS brings the timing into the correct range. Once within the acceptable range, finer adjustments might be possible through the pump sprocket position on the injection pump hub. Remember, precision is key when adjusting injection pump timing. Incorrect timing can significantly impact engine performance and longevity. If you are uncomfortable performing this procedure, consult a qualified TDI specialist.
