Drain the water separator daily or at every refuel, and replace filters at the specified interval. Water and debris that pass the separator reach the injectors, where the clearances are measured in microns and the repair cost is measured in thousands.
Service intervals
| Item | Interval and action |
|---|---|
| Water separator drain | Daily, or at every refuel on machines working in humid conditions. Drain until clean fuel appears. |
| Primary fuel filter | Per machine specification, typically at the shorter of the two fuel filter intervals. |
| Secondary fuel filter | Per machine specification. Replace both together where two are fitted. |
| Fuel tank | Drain water and sediment at intervals; inspect for contamination if the machine has been stored. |
| Filter housing seals | Replace with every element. Reusing or omitting seals is a leading cause of air ingress. |
| Fuel quality check | After any delivery. Contaminated bulk fuel puts every machine on site at risk. |
How to confirm it
- Drain the separator before opening anything
Open the drain at the base of the separator with a container underneath and let water and sediment out until clean fuel appears. Doing this first means the filter change does not push the water sitting in the bowl into the system.
- Clean around the filter housing thoroughly
Fuel system cleanliness is not a preference. Debris around the housing goes into the fuel system when the filter is removed, and the components downstream have clearances that a grain of grit will damage.
- Replace elements with the correct parts and new seals
Use the specified element and the seal supplied with it. Check that the previous seal came off with the old filter — a doubled seal is a common cause of leaks and air ingress, and it happens on the machines where the last service was hurried.
- Fill the new filter with clean fuel where the design permits
Pre-filling reduces the cranking needed to prime the system and reduces air ingress. Use clean fuel from a clean container, not from the drain tray.
- Bleed the system using the specified procedure
Follow the manufacturer's bleed sequence for that engine — typically filter head first, then the pump or rail. Bleeding in the wrong order leaves air trapped where it causes the most trouble.
- Run the engine under load, not just at idle
Air ingress and filter restriction often only show up under high fuel demand. Idling in the yard is not an adequate test, and a fault that passes it will reappear on site.
- Check for leaks and air after running
Inspect the filter housing and lines for weeping. Look for the classic air-ingress clue: fuel dampness that appears after shutdown, when the line is still under pressure.
What to do about it
If the engine is hard to start after a filter change, suspect air ingress: check the seal is correctly seated, the housing is tight, and air has been bled from both the filter head and the pump. This is the most common post-service fault in the fuel system.
If the separator bowl fills with water faster than expected, check the fuel supply. Repeated water loading usually means condensation in a bulk tank or a contaminated delivery, and the machine is not the problem.
If a machine develops smoke, misfire or power loss after refuelling, treat the fuel as suspect and take a sample before working on the injection system. Contaminated fuel has caused a great many injectors to be replaced unnecessarily.
Replace both filters where two are fitted, and keep the machine's fuel system records with the oil records. Fuel-system failures are far cheaper to prevent than to repair, and the records are what show a pattern developing.
Need the parts this covers?
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Request a quoteFrequently asked
How often should I drain the water separator?
Daily, or at every refuel — and more often in humid conditions or where fuel quality is variable. It takes less than a minute and it is protecting the most expensive components in the fuel system.
Can I run the machine if the fuel filter warning light is on?
Briefly, to move it to a safe place, and no further. A restricted filter reduces fuel delivery, which on a common rail engine can cause the pump to work harder and the rail pressure to fall. Change the filter rather than continuing to work.
Why does my engine lose power right after a filter change?
Almost always air in the system. Check the filter housing seal, confirm the housing is properly seated and tight, and bleed the system in the correct sequence. Air ingress after filter service is extremely common and entirely preventable.