Renault Trafic: Injector corrosion from water in the fuel — rough running and hard starting

Injector failure is common on the dCi Trafic and the named cause is specific and worth knowing: water ingress into the fuel. Water in diesel corrodes the injector internals and ruins fuel delivery, so the van runs rough, smokes, and becomes hard to start. Water gets in through a fuel filter that has not been drained or changed, through condensation in a tank that is often run low, and through poor-quality fuel — all of which are more likely on a working van doing long days and short refills. That makes this one of the more preventable faults in this report and one where the service history genuinely predicts the risk. Injectors are normally replaced as a set, which is what makes the bill matter on a van of this value.

• Hard starting, or long cranking from cold
• Rough or uneven idle, worst before it warms up
• Excessive smoke from the exhaust under load
• Knocking or diesel rattle louder than it should be
• Loss of power, or an engine warning light with fuel-system codes

Be there before it has been started, since cold starting is where this shows. Watch and listen as it fires: it should catch within a second or two and settle into an even idle, not crank repeatedly or shake for the first half minute. Stand at the back and watch the exhaust as it starts and again when it is revved warm, noting the amount and colour of any smoke. With the bonnet up at idle, listen for one cylinder sounding harsher than the others and for a diesel smell around the top of the engine, and look for wet fuel or a dark stain collecting around any injector. Then go to the paperwork, which is where the real answer is on this fault: check when the fuel filter was last changed and whether it has ever been drained, and read the invoices rather than taking an answer. Ask the seller whether the van is often run near empty and where it is normally fuelled, since both bring water and sediment into the system. Ask whether any injector has ever been replaced. If a workshop inspection is possible: an injector leak-off test names the failing injectors.

Parts involved: Body corrosion, Fuel injector.

$800 to $3,800 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “When was the fuel filter last changed or drained?”
• “Is the van often run down to near empty?”
• “Have any injectors ever been replaced?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.