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Contamination of Common Rail Diesels

Contamination of Common Rail Diesels

Here at Baileys Diesel Group we see too many cases of fuel contamination and repeated failure of replaced components due to incorrect repair of the injection system. Contamination can be caused by a wide range of things including but not limited to; water, particulates and petrol or other non-diesel liquids. We would like to cover a few things in regard to the prevention and correct repair of contaminated common rail diesel fuel injection systems.

Water in diesel can come from the service station, moisture created in the tank from cooling of fuel or even sucked in when submersing the tank in water i.e. a river crossing.

Water going through your fuel injection system, creates many problems. From lack of lubrication compared to that of diesel to the ability to almost instantly rust components of the fuel system due to the temperature of the fuel and components. This rust then creates contamination particles, however we are already past the filters and this only ends up at the injectors. While the injectors will usually be the failing component, damage has also been done to the rest of the system i.e. rust in the fuel rail, fuel pump and fuel lines. In some cases even the fuel tank/s will need replacement as many metal tanks will rust if water has sat in them. This means a thorough inspection of tanks is essential to eliminate all rust from the system. If all components are not replaced this rust will dislodge and end up passing into the brand new set of injectors or stop the pump from working eventually.

Above (L-R): Separated water, emulsified water

In many cases water contamination does not set off the factory water alarm whether this be because it has been emulsified or the filter has not displaced a large enough amount to bring on the warning lamp. In this case the vehicle will usually run as usual however rapidly wearing components. Once stopped these vehicles can often present a non-start condition or hard to start condition. Once running, lack of power and rough idle are indications contaminated fuel may be the issue.

While modern diesel vehicles are equipped with OEM water traps and sensors in their filters, often this is not enough or they do not alert the operator quick enough. This is where extra preventative measures should be taken. Look for reputable service stations with high turnover as there is less chance of large amounts of water being in the fuel. Always keep your fuel receipts! If you have access to “cheap” diesel through the workplace or farm tanks, avoid this in your common rail vehicles it will NOT save you money in the long run. Ensure tank breathers are not blocked and if possible extended above where you may get water to save the tank pulling in a large amount of water in a water crossing event. Fit a secondary filter, we recommend a 2 micron secondary filter that also includes its own water trap. This gives you some water trap capabilities after the main filter and warning indicator, that way if water is coming through your main filter but it hasn’t yet set off the indicator you should catch what water makes it past until the indicator is set off. Installing a pre-filter will separate water yes, however when the water indicator is triggered you now have water in both your pre and main filters with the main filter now reaching its water trapping capabilities meaning the indicator is the last line of defence leaving you clueless to water in your system until a lot of the time it’s too late.

If you do happen to have your water indicator go off in your vehicle, stop driving immediately and drain your filter. We would also recommend having your tanks drained and cleaned as soon as possible whilst getting your fuel system checked for any signs that the water made it past the filter.

Particulates can end up in the fuel system in many ways including, poor cleanliness during maintenance, dirt ingress when refuelling through the tank filler, dust through tank breather and diesel bug (usually grows when water is present).

Example of diesel bug

These particulates do not have to be large, it’s the smallest particulates that will cause the damage. With most factory filters ranging between 5-10 microns and injector clearances down to 2 microns. Anything between 2 and 5 microns will cause premature wear in your common rail injectors. For example on how small this is the average human hair is around 60-80 microns in diameter, so these particles damaging your fuel system are virtually invisible. This is the biggest reason we recommend installing a 2 micron secondary fuel filter on your common rail vehicle. Many people will say a 2 micron filter will cause restriction however our fuel manager 2 micron filter flows at 300LPH the exact same flow rate as a 30 micron fuel manager filter. If your 2 micron filter becomes blocked after catching all the particles your factory filter has allowed through causing a fuel restriction this is better than those particles going through your injectors considering a replacement filter will set you back $40 and can be kept in the vehicle rather than thousands for injectors.

To keep chances of particulate contamination to a minimum take extra caution when replacing fuel filter or working on any part of the fuel system. Try to keep the engine bay and areas around fuel filler and tanks as clean as possible.

Above (L-R): Undamaged valve plate under microscope, valve plate erosion due to contamination under microscope, spindle damage due to contamination under microscope

Filling a diesel vehicle with petrol happens more regularly than you would think. However there are usually two outcomes. One being you realise before starting the car or you drive the car until an issue arises.

If you do happen to fill your diesel with petrol and do not start the vehicle, get the vehicle towed to our workshop or your nearest mechanic. If the vehicle is not started the tank can be drained and re-filled with diesel with no issues. Some tanks may need to be removed to achieve proper draining of petrol.

If the vehicle is started and driven, once the petrol reaches the injection system the damage is almost instant. Although it may take a while for the car to “sound bad” or not “run well” the damage starts occurring straight away. Unlike diesel, petrol has dramatically less lubrication properties and the diesel fuel injection system relies on the diesel to lubricate all the components. This causes all components to become much hotter than usual and running with no lubrication and a greater amount of heat, rapidly increased wear occurs. Once petrol has run through the diesel injection system no matter the amount, all components should be replaced, thus preventing premature failure. If only failed components are changed i.e. injectors, the premature failure of other components not replaced can then produce contaminate particulates which will then be passed through the new injectors likely causing them to fail again much sooner than expected.

Above (L-R): Intake pickup, tank internal photo after draining through bung

For warranty purposes replacing all components is necessary to ensure warranty of new products is not affected.

These components are what we recommend to be changed when repairing a fuel system that is contaminated.

  • Injectors
  • Fuel Lines
  • Fuel Rail
  • Pump to Rail Fuel Line
  • Fuel Pump
  • In-tank pickup assembly (cleaned or replaced)
  • In-tank pump if applicable (if damaged or no longer operating)
  • Fuel tank cleaned and replaced if necessary (if any sign of rust)

There are two easy to see tell tales of contamination when replacing injectors. The first would be the fuel filter. If your fuel filter is completely black or “sludgy” and “slimy” there is a good chance your vehicle has suffered a contamination related failure.

Severely contaminated fuel filter

The second is the inlet filter in the injector itself. Here are pictures of contaminated and non contaminated.

Above (L-R): New, rust particles, severely contaminated

Many of the vehicles we do this work on are covered through their comprehensive insurance policy. We highly recommend knowing whether your vehicle is covered for contamination and confirming with your insurance company what their coverage is. Often claims require receipts of recent diesel purchases so this is a big reason to hold on to your fuel receipts. The insurance company should be notified asap when contamination is found and can aid in what they require for the claim to be processed. Never continue with the repair until confirmed by insurance.