Check For Damage

febi explains the importance of regularly inspecting high-pressure fuel pump cam followers to protect against consequential damage.

VAG has been using fuel-stratified injection (FSi) to power their petrol engines since 2000. This system was designed with the aim to improve fuel consumption and engine efficiency. By running the engine with leaner fuel mixtures, emissions are lowered. As with any

components that operate in extreme conditions, fuel pumps are susceptible to wear and tear. Thus, it is advised to regularly inspect high-pressure fuel pump cam followers.


Stratified fuel injectors are situated directly in the cylinder head so that fuel can be directly injected into the combustion chamber at high pressure to increase atomisation. The fuel cloud is sprayed relative to the position of the spark plug, thus reducing areas of an incomplete fuel-to-air mixture burn for increased efficiency.

What makes these engines unique is the high-pressure fuel system. It comprises a high-pressure fuel pump (HPFP), fuel rail, high-pressure injectors, a pressure regulator and sensors to feed back fuel pressure readings to the engine management.


The pump’s piston is run off lobes on the camshaft with a bucket type cam follower which is case-hardened to take the stresses between the camshaft and the pump piston.

However, early cam followers had been reported to wear out quickly. In the more serious cases, this led to damage of both the camshaft and fuel pump. As a result, VAG released a technical service bulletin highlighting an improved cam follower that was treated with better case-hardening to prolong its service life. This pump design was in production for about 10 years and has since been superseded by a single cylinder pump with a roller on the end of the piston to reduce friction.

Symptoms of cam follower wear:

  • Increased engine noise
  • Loss of engine power
  • Illumination of engine management lamp
  • Fault codes logged by engine management as a result of mechanical fault relating to fuel pressure loss and poor regulation

If excessive cam lobe wear has occurred, the maximum pump piston lift is limited. This causes fluctuation in fuel pressure. Cam lobe wear can lead to deterioration in the base of the fuel pump cam follower, leading to damage of the fuel pump piston base.


In conclusion, febi advises that the HPFP cam follower should be inspected for wear periodically as it is better to replace the follower before it has had the chance to cause pump and camshaft damage.

When choosing a replacement HPFP cam follower, one should consider the material quality. febi’s HPFP cam follower (part no. 37162) is fully precision engineered to OE specification to provide reliable performance.

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Published on: May 4, 2020

Filled Under: Fuel, Technical Articles

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