Scaz93 said:

Ahh I see. Was hoping to avoid a full new set of injectors. Hoping it could have been seals or o-rings. Would this only really happen with freezing temperatures?

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Scaz93 said:

Had the issue last few days when the temperature was above 5c so the glow plugs wouldn’t even be on. Will get a leak off kit and test the injectors

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Nodge68 said:

The injectors can't really be repaired except by Bosch. The parts aren't available, so injector "reconditioners" simply swap parts about to make the injectors work again. Unfortunately this doesn't guarantee a perfect injector, and also changes the injector characteristics, making coding them a pointless exercise. Bosch will issue new codes calculated on the actual injector performance.
However new vs Bosch rebuilt injectors, it's still better to simply install new injectors.
There's nothing to stop a single faulty injector from being replaced, rather than the whole lot.


A spill or leak back test can't be done on these injectors as the return line is held at 10 bar to ensure the injectors always have fuel in them. The injector uses 10 bar of fuel pressure as part of a hydraulic linkage between the piezo firing element and the injector needle . No pressure in the return would prevent the injectors from firing at all.

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Scaz93 said:

Ahh I see. Thanks so much for spending the time to reply ! How do you test for a faulty injector if you can’t do a leak back test? Thank you

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Nodge68 said:

The only true way to test these injectors is to have them tested with specialist equipment. This will test for leaking down over time, and also the firing mechanism to check it can inject fuel exactly as requested by the ECM. The ECM can command several injection pulses per firing stroke, so the injectors must respond instantly to commands, or running issues arise.

Some ECMs also allow for the display of injector compensation on suitable diagnostic equipment, but I'm not sure if the later ECM outputs this data. I know my earlier ECM doesn't output compensation values, so I would prove a faulty injector by substitution or have them tested.

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