ESP Replacement: Simmering Guide & Tips

Hello everyone,

bei meinem G4 AHF ist seitdem ich Ihn fahre (gekauft mit 2 Jahren und 48 TKM - der Golf nicht ich ) eine leichte Feuchtigkeit am Simmering der ESP zu bemerken. So far.
'It's not a real problem, but now, after 5 1/2 years and 140,000 km, it's slowly becoming more of an issue. So, I plan to remove and reseal the ESP soon. It's not a big deal; I've done it before on my wife's Passat AFN. However, the AFN had a one-piece impeller, while the AHF has a two-piece one. Now, the 'experts' in Erwin (siehe Fehlerdatenbank) state that the large nut on the pump shaft that secures the gear with 3 screws must not be opened, as in that case, the pump could no longer be adjusted using workshop tools. I don't believe everything people write. For example, everyone says that you can't reseal a ' ' because you can't adjust it without a dynamometer, but it is possible. After studying the ESP design and function, I've considered determining the pump stroke at TDC before removal, using a dial gauge, and marking the ESP shaft and hub before loosening the central nut. Now, here's my problem: since I've never worked on VP diesel engines before, I have no experience in measuring the pump stroke.
Therefore, here's my proposed approach. If anyone has relevant experience, I'm mainly looking for confirmation of my plan, or suggestions for modifications.

1. Engine at Top Dead Center (TDC) for cylinder 1.
2. Insert the measuring instrument and set it to 2 mm.
3. Rotate the motor backward until the gauge stops moving.
4. Set the measuring instrument to zero.
5. Slowly rotate the motor until it reaches the top dead center (TDC) position, and then determine the pump stroke.

I wanted to set the ESP (Electronic Stability Program) to this value before installing the hub, and then make a dynamic adjustment using VAG-COM.

Does anyone have the exact lift values for the AHF pump at the top dead center (TDC) position?

Thank you in advance, Merry Christmas, and a Happy New Year!

Your approach is correct. Setting the dial indicator to approximately 2 mm (OT position) only serves to achieve a certain preload of the spring force of the clock hand clamps, ensuring that the measuring tip (extended clock hand clamp) of the clock makes contact with the pump housing. You could also set it to 4 mm; it doesn't matter for the measurement because it's a differential measurement. If it happens to be a bit tight, because it can sometimes be quite cramped, then when you turn it back – until the pointer no longer moves – gently press on the top of the measuring tip with your finger.
The hub setting is usually 0.9 +/- 0.02 (when adjusting; a larger tolerance is specified for testing). Start by setting it to this value, then try it with VAG. If it's roughly correct with VAG, then the hub is set correctly (although it doesn't always match, VAG is more precise).

If you know the correct pump stroke, you don't actually need to measure it beforehand (it might be misadjusted, especially if it hasn't been checked since the last timing belt replacement). The important thing is that you measure the stroke and ensure that cylinder 1 is being used (meaning the shaft isn't rotated by a multiple of 90 degrees).
"If you need more information, I can check the RepLeitfaden again, but I need some details (for item 2, item 3, identification number, year of construction, etc.) otherwise I won't be able to access it."

Thank you, Cetano.

The reason for the default setting was already clear to me. I just didn't have a clear idea of the exact measurement. I have the VAG repair manual on my computer. Unfortunately, it doesn't provide much information for the specific job we're doing – it's really frustrating from VAG. If it were up to them, we'd have to replace the ESP unit because of a seal. If you happen to have the torque specification for the large nut on the ESP, it would be great if you could share it with me. Otherwise, I'll use the 55 Nm value for the one-piece pump impeller and secure the nut with Loctite.
'I will definitely measure the piston stroke before removing the pump, just as I will take the MSW (cool/warm/stationary/idle) values using VAG-COM before I start. I will also measure the pump's internal pressure beforehand. Regarding the top dead center (TDC) of the first cylinder, since the valve cover has to be removed anyway, it's not a problem to identify the camshaft position to determine when the engine is at TDC, and there's also the locking pin for the ESP drive wheel, which only fits when the first cylinder is at TDC.'

I once used Autodata (a 2005 edition).
"there it says:"

For Volkswagen Golf (1998-2005) with 1.9D TDI engine, engine code: AHF, the following:
-Mother injector pump rotor, 20 Nm, +90 degrees - and as a note: use new "screws" (?)

As an example of a single-piece timing belt pulley, I checked the specifications for the Golf II engine with motor code JR:
Mother injector pump rotor, 45 Nm (no indication).

I'm not really getting any wiser from this...

I'm only familiar with the "+90 degree" marking from expansion bolts; I haven't heard of "expansion nuts" before.

---->> https://community.dieselschrauber.org/en/viewtopic.php?p=72950 (?)


Here's some more information about fuel injection timing (from Autodata):

Example JR: Position of the KW 0 ground before Top Dead Center (TDC) - Pump position: 0.90 +/- 0.02 mm after Bottom Dead Center (BDC) (corresponds to a lift of 0.9 mm when the motor is at TDC, but the pump is already further along; therefore, measured after BDC).

Example AHF: Position KW 0 (crankshaft) relative to the camshaft (camshaft) - and no indication of pump position, instead a stylized image of the flywheel with an additional marking for the start of injection, and a note indicating the use of special tools: "Pointer/Special tool".

Here, common sense is probably needed again.
Ultimately, VAG-Com will fix it.

Thank you.

The AHF has a two-part toothed pulley on the ESP - a large one with an outer toothed ring that is attached to the hub with three M8 screws (there are two different versions) through three elongated holes. The inner part - the hub - is attached to the cone of the ESP shaft. This cone, unlike ESPs with a one-piece drive pulley, does not have a keyway, which makes things a bit difficult because the basic adjustment of the ESP is lost when loosening the large nut - the relationship between the position of the pump piston and the position of the holes in the hub and the pump housing for the locking pin must be re-established - according to VAG documentation, this is not intended.
After replacing the seal, this initial adjustment must first be made using a dial indicator to ensure the engine runs properly. There's no point in trying to start the engine by manually turning the pump; only then should VAG-COM be used.


In a two-piece drive wheel, the outer wheel on the hub is rotated to adjust the ESP (Electronic Stability Program), not the inner part itself – that's why there are elongated holes. I was referring to the torque for the nut that secures the hub (the inner part of the drive wheel) to the cone of the ESP shaft. For the Passat AFN with a one-piece drive wheel, the torque is 55 Nm.

'Example AHF: Position the crankshaft at 0 degrees before top dead center (TDC) - and instead of specifying the pump position, provide a stylized image of the flywheel with an additional marking for the start of injection, along with a note indicating the need for special tools: 'Pointer/Special tool'.'
This refers to another marking on the flywheel that is used when determining the OT (Outer Top Dead Center) position of the engine while it is disassembled, using a special indicator.


'In any case, before dismantling or disassembling anything, I will record and document all possible values and dimensions, as well as make various markings.'

Merry Christmas and a Happy New Year!

Okay, I understand... if the wedge were there, it would be far too simple, just like with a one-piece timing pulley.
I think that even if you're given all the individual parts, you can probably get it working again with some simple tools (to get the basic settings right), it would just take a little longer (because the pump doesn't stay still in every position).


likewise beautiful holidays