Workshop calculator
Injector leak-off and balance test calculator
Injectors are judged by comparison. On a common rail diesel a worn injector returns much more fuel than the others; on a flow bench a restricted petrol injector delivers less. This calculator compares each cylinder with the average of the others.
Test
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How to use it in a diagnosis
- Run the leak-off test at warm idle for a fixed time (often 1–2 minutes), or a flow test for a fixed time per injector.
- Enter the volume from each injector in ml.
- Leak-off: more than about twice the average of the others is suspicious. Flow: more than about 5 % from the average is worth a closer look.
Questions mechanics ask
How much injector leak-off is normal?
It depends on the injector type and test, so compare injectors with each other. As a rule of thumb, an injector returning more than twice the average of the others is worn or leaking internally.
Should I replace an injector because of balance (correction) values?
Not on balance values alone. Confirm with a leak-off test and a compression test first: low compression on a cylinder makes its injector correction look bad too.