Injector Leak-off Test
An injector leak-off test measures how much diesel each common rail injector returns, to find worn injectors.
What is Injector Leak-off Test?
Small bottles collect the return fuel from each injector. Results are compared between injectors and with specifications. It is a quick, low-cost test. The test is usually done at idle and while cranking; manufacturers may specify the run time and limits. Piezo and solenoid injectors behave differently, so compare only identical injectors.
How it works
Worn injectors leak more fuel back to the return line.
Why it matters for your car
High leak-off causes low rail pressure and hard starting. Replace or recondition the faulty injector, then code it.
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