Introduction
If you own a common rail TDI you have most likely heard of or been warned about the CP4 high pressure fuel pump failures. What are the causes of the issues? Should you be concerned? How can you prevent these issues?
The main cause of a CP4 pump failure is a lack of lubrication. The pump uses the diesel fuel to lubricate all internal moving components. Running the vehicle on poor fuel or running the vehicle out of fuel can lead to a lack of lubrication and allow metal-on-metal contact within the pump. Once the vehicle has had a lack of lubrication there will normally be signs of metal shavings within the fuel filter housing.
Ignoring the early warning signs of a failure can lead to extensive engine damage caused by the shavings entering the fuel system and going through the injectors. Once the metal shavings enter the fuel, you will need to replace most of the fuel system components. Items that need to be replaced to get the vehicle running properly again include a new high pressure fuel pump, auxiliary electric fuel pump, in-tank lift pump, injectors, fuel filter housing, fuel rail, and all fuel lines.
These items will cost well over $4,000 just for the parts! But how do you prevent this failure?
How can you prevent early failures?
1: High Quality Fuel: The CP4 fuel pumps are highly sensitive to fuel quality. We suggest only purchasing fuel from reputable filling stations that have a high turnover of diesel fuel.
2: Adding Lubricity with a Diesel Fuel Additive: Using a fuel additive like Opti-Lube or Stanadyne which have been proven to increase the lubricity of the fuel can help prevent metal-on-metal contact in the pump.
3: Regular fuel filter changes: The fuel filter on the CBEA & CJAA common rail engines should be changed every 20k miles. During the filter change the filter housing should be inspected for metal shavings in the fuel. If metal shavings are found you should look into replacing the pump.
What do you do if your pump is failing?
Early warning signs of a pump failure will be present in the form of metal shavings in the fuel system, power loss, check engine light related to fuel pressure, and difficulty starting.
One of the most popular options is retrofitting the system with the more durable CP3 pump. The CP3 pumps do require an ECU tune for proper operation with no fault codes.
Swapping to the CP3 pump will give you peace of mind knowing your pump isn’t as sensitive to the issues that lead towards the CP4 pumps failing.
If the metal shavings have entered the system you would need to replace the entire fuel system using a high pressure fuel pump replacement kit.
How common are the CP4 high pressure pump failures?
Overall we feel the pump failures have been overly exaggerated. The pumps do fail if the vehicle is not properly maintained but owners who use additives and do regular maintenance should not be overly concerned. Using additives and routine fuel filter changes should help prevent the failure or at least notify you of the early signs before the metal is allowed to enter the rest of the system.
