DIY leak off test results - what do they mean?!

[Melvin C. Yowser]

I did a leak off test to my 2000 W202 C220 CDI. I did the test 3 times. On my auto C class once you've activated the starter it will turn over for a few seconds without holding the key. For each test I did this 4 times and then measured the quantity of diesel that emerged from each injector. The results were pretty much the same on all 3 occasions:

Injector 1: Just over 1ml
Injector 2: Just over 2ml
Injector 3: Under 1ml
Injector 4: Just under 2ml.

The question is: do these results actually mean anything?! Is this sufficient proof that one or more of the injectors are faulty? As I'm looking at £200 to supply and fit each replacement injector, I'd greatly appreciate any wise input anyone could give me!

Cheers!

 

[GEORGEROV]

Hi Melviin. As a first step I would have the injectors ultrasonically cleaned by a Bosch or Lucas service centre.

 

[Ellsy Tanners]

I think those results show injectors are fine.

A faulty injector has a constant dribble coming from it.

 

[Autofix]

Common rail leak off will only make sense if measured properly. The amount of leak off must be expressed as a capacity, cubic centimeters, mililitres etc over a given period of time. Also the injectors must be disabled during the test.
I use graduated tubes for testing so I don’t have the quantities off the top of my head but if you are stuck I can look them up for you later.

Do you have a reason to suspect the injectors?

 

[Melvin C. Yowser]

Cheers for the feedback!

I certianly do suspect my injectors because the car won't warm start even though it's had a new battery, new plastic fuel lines and a crank sensor fitted. During the tests, following advice from the forum, I disconnected the cam sensor - does that 'disable' the injectors? Any further info you can give would be much appreciated!

 

[Ellsy Tanners]

When a car wont start with a faulty injector, it is normally just one that has a huge difference in leak off amount compared to the others.

It looks like all 4 of yours have roughly the same amount of leak off, so to have all 4 go down at once is very unlikely IMO.