Diesel knock / pinking

Faulty Diesel Injector(s)

A problem resulting from worn parts or sticky nozzles are a delay in the start of injection or incorrect pre-injection which in turn results in rough running, diesel knock or pinking.

For peace of mind, send your injectors in for testing.

Fuel Quality and Contamination

Contaminated fuel will reduce the life of your diesel injection equipment. Water robs the fuel of its lubricity, which will cause premature wear. Transferring fuel from drums also results in contaminated fuel, and we also see failures due to the addition of AdBlue in diesel fuel.

Blocked Fuel Supply or Dirty Fuel Filters

The first thing to do when fault-finding is to replace the fuel filter with and O.E. one. Also, make sure that there are no blockages in the fuel supply lines.

Faulty High-Pressure Pump

If the pump is defective, there will be a “Low fuel pressure” problem. This problem arises if the pump “breaks up” internally causing swarf and iron filings to get into the fuel system. Usually, this causes damage to the diesel injectors, and unless the complete fuel system is drained and cleaned, the problem will arise again.

Faulty Pressure Regulator or Sensor

Most vehicles have a pressure regulator fitted on the high-pressure pump and a sensor installed on the rail. If either of these is defective, there will be running issues like hard starting, uneven tick over and the vehicle cutting out when increasing the RPM.

Cam and Crank Sensors

Check that the sensors are not loose, cracked or damaged as they are not very expensive. If you have any doubts I would recommend replacing them.

Injector Blow-By or Injector Seat Leaking

Injector “blow-by” can be the cause of some of the following symptoms:

  • Hard or difficult starting,
  • Erratic or uneven tick over,
  • Lumpy running,
  • Smoke on acceleration,
  • Black tar around the injectors and a chuffing sound from the engine when running.

Injector “blow-by” occurs when the injector does not seal against the injector seat in the cylinder head.

On some engine applications if this continues severe engine damage could result because the ECU will over compensate the fuelling, causing piston wash or over fuelling. Even if the injector is removed, cleaned, a new copper washer fitted and then replaced, it will not always rectify the problem. The only way to remedy the fault is to reface the injector seat in the head using a seat cutting tool.

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