Common-rail injectors are built to tolerances of a few thousandths of a millimeter and work at over 1,500 bar. They don't usually wear out from age. They're killed by what's in the fuel: water, dirt, and debris from elsewhere in the system. Keep the fuel clean and dry, and a set of injectors can last a very long time.
1. Buy clean fuel
- Use reputable, high-volume filling stations. Fuel turns over quickly there, so there's less time for water and sediment to build up.
- Avoid filling up while a tanker is delivering to the station. The delivery stirs up sediment in the underground tanks.
- Be wary of very cheap, informal or unknown fuel sources. One tank of contaminated diesel can cost more than years of fuel savings.
- Use the diesel grade your manufacturer specifies. Modern engines with a DPF are designed for low-sulphur diesel (50 ppm or 10 ppm). See How to Make Your Turbo Last for why this matters for the turbo and DPF too.
2. Fuel filters: the right filter, on time
The fuel filter is the injectors' only real protection.
- Use filters that meet the OE specification. Common-rail filters need much finer filtration than older systems. A cheap filter that fits isn't necessarily a filter that protects.
- Change them on schedule, and sooner on gravel roads, in dusty areas, if you're filling up in rural places, or after any fuel you're unsure about.
- Change filters cleanly. Clean around the housing before opening it, and cap any open fuel connections.
- Don't pour fuel into the clean side of a new filter to prime it. Unfiltered fuel goes straight to the pump and injectors. Use the hand primer or the manufacturer's bleeding procedure.
3. Water: drain it and never ignore the warning light
Water is the number one injector killer. It corrodes precision parts, removes the lubrication the pump and injectors depend on, and causes scoring and seizure.
- Drain the water separator at the interval in your manual, more often in humid conditions or if you're unsure of your fuel.
- Never ignore a water-in-fuel warning light. Stop and drain the separator as soon as it's safe to do so.
- Consider an additional fuel pre-filter with a water trap if you work on farms, travel remotely or tow far from main routes. It's a cheap upgrade that catches contamination before it reaches the OE filter, and it's very common on bakkies that work in tough conditions.
4. Don't run the tank close to empty
Sediment and water collect at the bottom of the tank. Running low draws them into the system, and an empty tank lets air in, which then needs bleeding out. Keep it above a quarter where you can.
5. Bulk tanks, jerry cans and stored diesel
Farm tanks, site tanks and jerry cans cause a lot of injector failures.
- Keep containers clean and sealed, and use them only for diesel.
- Fit a filter and water separator on the bulk tank's dispensing line, and drain water from the tank regularly.
- Keep bulk tanks reasonably full to reduce condensation, and use stock in rotation. Diesel doesn't keep indefinitely, so think in months, not years.
- Watch for the "diesel bug". Microbial growth forms where water meets diesel in storage tanks. It shows up as slime, black sludge or rapidly blocking filters. Treat the tank with a proper biocide and clean it out, or the problem keeps coming back.
6. Additives: what they can and can't do
- A quality diesel additive (detergent or lubricity) from a reputable brand may help keep deposits down, particularly if fuel quality is uncertain.
- Additives can't repair a worn nozzle, a leaking control valve or water damage. If an injector has failed, it needs testing and repair, not a bottle.
- Never add petrol, paraffin, two-stroke oil, ATF or used engine oil to modern diesel. These old-engine "tricks" damage common-rail pumps and injectors and can block the DPF.
7. Keep up with engine servicing
- Change the oil and filter on time. On HEUI engines, the injectors are driven by engine oil, so oil quality directly affects injector performance.
- Check the oil level between services. A rising oil level can mean fuel is leaking into the oil from a dripping injector. Have it investigated rather than draining off the excess.
8. Watch the sealing washers
A failed injector washer lets combustion gas escape past the injector. Act early if you notice:
- A ticking or chuffing sound near an injector
- Black, tar-like build-up around the top of an injector
Caught early, it's a washer replacement. Left alone, it can lead to a seized injector, oil sludge, and on some engines turbo and engine failure.
9. The early-warning check most owners miss
At each service, ask your workshop to read the injector balance (correction) values with a scan tool and note them down. The ECU uses these values to compensate for each injector. When one cylinder's value starts drifting away from the others over a few services, that injector is wearing, long before you notice smoke, knocking or hard starting.
It takes a few minutes and costs very little, and it turns an emergency repair into a planned one.
10. Keep it clean when the fuel system is opened
Contamination introduced during repairs is a real cause of injector failure.
- Clean around fittings before you undo them.
- Cap every open port and line immediately.
- Never reuse high-pressure lines or sealing washers where the manufacturer specifies new ones.
Warning signs: don't wait
Get the injectors checked if you notice hard starting, rough idle, black or white smoke, knocking, power loss, higher fuel use, a fuel smell, or a rising oil level. See Diesel Injector Problems: Symptoms, Causes and How to Test.
Injectors and fuel system parts from TDC
Turbo Diesel Components supplies diesel injectors, injector components and sealing washers for passenger, commercial and industrial applications. Search our catalogue or contact our team for help.