Common faults with VAG vehicles with tandem fuel and vacuum pumps

Main parts   

This post will investigate the two most common faults that occur in the VAG group's tandem pumps.

These types of pumps are installed in those engines equipped with the pump injection system.

The tandem pump unit is a set of two pumps in one unit with very differing functions.  The entire pump assembly is driven by the camshaft.

One of the functions of the assembly is the vacuum pump; which generates the vacuum for the brake servo. The second function of the assembly is a fuel pump which sucks fuel from the fuel filter to the feed pipe located in the cylinder head and supplies the injectors.

The working pressure of this pump varies between 8 and 12 bar depending on the model.

FAULTS

The most common faults in this type of pump are as follows:

1 Loss of fuel.

2 Mixing of oil with fuel.

PROCEDURE AND SOLUTION

The repair procedures for either of the two faults are practically the same except for the additional tasks required in the case of oil and fuel mixing, which are:

• Fuel filter replacement
• Checking the engine oil level

 In both cases the problem can usually but not always exclusively be located in one of the gaskets or on the pumps main shaft oil seal.

Set of gaskets   

Fault in the suspension level control system fitted on Audi Q7

We are going to diagnose and repair a fault that affects Audi Q7 models (4L) manufactured from 2007.

These models are equipped with Adaptive Air Suspension (AAS) self-levelling suspension system.
The diagnostic fault codes recorded in the Level Control Unit (J197) are:

• Code 1781 - Extreme inclination of the vehicle, maximum threshold value exceeded

• Code 1400 - Level control, maximum threshold value exceeded

Navigator and Multi-Media Interface (MMI) Control Panel

SYMPTOMS

The vehicle is unstable and wanders on the road and remains inclined to one side and the reference ride height position cannot be activated and/or adjusted on the menu on the Multi-Media Interface (MMI) screen within the vehicle.  

• The residual pressure check valve on the spring/damper assembly remains closed.

Navigator and Multi-Media Interface (MMI) Control Panel

Navigator and Multi-Media Interface (MMI) Control Panel