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4JX1 - Problems with the injectors – Oring problems

Problems with the injectors – oring problems

This amounts too usually, one of three problems:

  • Diesel in coolant [oily scum found on top of radiator coolant, under the cap];
  • Coolant in the diesel [green coolant in the diesel tank];
  • Diesel in the oil [increasing oil volumes on stick]

A set of removed injectors, with 3 litres of coolant in the diesel system. The orings were flattened, softened or compromised.


Diesel in Coolant:

Diesel in the coolant or coolant in the diesel is a profound and simple solution of replacing the injector tube o-rings. Often there is loss of coolant as the initial symptom, so I ensure that I check the levels in the overflow tank every morning before use and check the oil level. If there is an oil slick in the radiator or an oily brown sludge, you have identified the problem.

The coolant loss can occur for a lengthy period before a “slick” appears or there is coolant in the fuel tank.

Coolant in the diesel:

Again, if you are losing coolant, but the engine is not overheating, check the glass bowl [if you have a secondary glass bowl in your fuel system] or check the diesel tank. [12mm nut in bottom of standard fuel tank, drain a litre to check, showing as “green globules”].

Also, for final confirmation, check the fuel filter at change, by turning upside down into a white container and see if you have any coolant contamination – usually green, if you used green coolant as recommended.

Oring damage:

Compromised orings in the sump, shows as a failure to “enable injectors” due to low oil pressure. Can be checked easily by adding 1 litre 5W-30 oil to the sump and starting. If engine starts, orings in sump should be replaced. Fault due to ingress of air past the orings and diesel degrading – orings go very soft to touch.


Fixing problem:

This type of contamination can be rectified by replacement of the injector and injector tube orings after removal of the injector tube using a special tool.

4JX1 Removal Tool CNC version

Injector sleeve removal tool

The problem is, the diesel will degrade all orings that it comes into contact with as the OEM orings are not high enough quality and resistant to the diesel. The “4JX1 experts” have sourced quality orings and these now form a replacement kit.

Should injector orings be replaced on a maintenance plan??

Yes, and between 60 to 80,000 km

Orings likely to be damaged by the diesel ingress:

Injector tube – 8
Injector – 1
High pressure oil supply – 2
End of oil rail – 2
Sump pickup – 2
ORPS oring – 1
Radiator oring around top – replace radiator [welded Al or standard fitting]
Following hoses may require replacing after diesel in coolant (in order of most likely to be damaged):-

  • Hose underneath the turbo;
  • Small hose between thermostat housing to turbo;
  • Small L shaped hose from block, below alternator, directed to rear of motor;
  • Radiator top hose;
  • Radiator bottom hose;

Diesel in the oil:

This is very serious and related to injector failure, with the internal orings failing and allowing diesel to enter the oil. This shows as an increase of oil volume by an increase on the oil measuring stick. Park in same place and check when cold. A secondary check is the “smell test”, simply smell the oil on the stick and see if it has a “diesel smell”.

Unlike the previous two, diesel in the oil has some serious consequences.

It can result in overfilling of the sump [I have had found an extra 4 litres of diesel in the sump in less than 140km] lessening and surging of oil pressure and in some cases a runaway engine that must be stalled to stop the engine. This was part of the original series of recalls by GMH of the vehicle.

Cause is a failed injector, which may be due to a broken internal spring or plunger or just defective internal orings. There is no “fix” at present, but the “experts” are working towards a suitable oring and spring replacement.

At present, identify the failed injector and replace.

Head Breakdown – Parts


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