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Discussion Starter · #1 ·
Recently I doing back leak test for all 4 injectors and find as below
Bottle Liquid Water Drinkware Water bottle

from Left to the Right is Injector 1 -4 and 5 minute engine running
any one know how much back leak volume minimum-maximum for Delphi Injector
Engine running with no issue just curious with above.

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7,924 Posts
Interesting question. I had a look on the internet and the following link offered a sensible non technical reply - see poste entry no 6 by Top Bloke
He states "The maximum permissible return quantity is 3x as large as the smallest return quantity measured"
Your four bottles appear to be very similar although you haven't quantified the individual ml's. Visually I wouldnt think there is any concern there.
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963 Posts
Ed; funny I read the same article:)

Si Ario, looking at the results of your leak-off test, these bottles aren’t calibrated containers so it’s difficult to judge the amounts involved. You would need to empty each container into a beaker or something with a graduated scale to accurately measure.

I’d expect the leak off rates would be defined in the Delphi manual but not so sure it will be a fixed min/max amount. The amount of fuel will vary according to fuel density & temperature, pressure and flow being supplied by the HP pump also the engine load and RPM. You should run the test about three times to get a better idea and also blip the throttle a few times during each test.

According to that link Ed gave, someone said: On Bosch injectors on Vauxhalls we employ the recommended procedure to measure diesel injector return quantity

Connect up test rig.

Start engine

Let engine run until one of the measuring cylinders is filled completely

Stop engine

The maximum permissible return quantity is 3x as large as the smallest return quantity measured

Example that is OK:
Measuring cylinder:
1 41 ml
2 44 ml
3 50 ml
4 46 ml

Maximum permissible return quantity: 41 ml x 3 = 123 ml
All the injectors are in good order.

Example that is not OK
Measuring cylinder of injector
1 50 ml
2 18 ml
3 18 ml
4 10 ml

Maximum permissible return quantity: 10 ml x 3 = 30 ml
Injector 1 has too large a return quantity, possibly needs replacement.
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