R class compression test is failing on STAR. one cylinder shows 0.
Thread Starter
Member
Joined: Sep 2017
Posts: 173
Likes: 25
From: UK
Mercedes R320L CDI 4MATIC 2007
R class compression test is failing on STAR. one cylinder shows 0.
Hi to all,
i am having hard start when engine cold, started digging in what could be the cause. Glow plugs ok, glow plug relay as well. Then i thought it could be the injector problem?
when i was looking at injector testing on star diagnosis under common rail diesel injection CDI ->guided diagnostics, found the compression test (i assume that is the cylinders compression test??), performed it and here we are: cylinder 1 gives 0 (per 1/rpm).
So does that mean the compression is 0 at that cylinder?
Does anyone know how this compression test is performed? how does the system determine the pressure? is it by using injectors? can the injector fault be the zero value measured then?
After the car starts up, it works ok on idle and while running.
Greatly appreciated any response.
Thanks!
i am having hard start when engine cold, started digging in what could be the cause. Glow plugs ok, glow plug relay as well. Then i thought it could be the injector problem?
when i was looking at injector testing on star diagnosis under common rail diesel injection CDI ->guided diagnostics, found the compression test (i assume that is the cylinders compression test??), performed it and here we are: cylinder 1 gives 0 (per 1/rpm).
So does that mean the compression is 0 at that cylinder?
Does anyone know how this compression test is performed? how does the system determine the pressure? is it by using injectors? can the injector fault be the zero value measured then?
After the car starts up, it works ok on idle and while running.
Greatly appreciated any response.
Thanks!
Thread Starter
Member
Joined: Sep 2017
Posts: 173
Likes: 25
From: UK
Mercedes R320L CDI 4MATIC 2007
printscreen
attached the print screen. it can be seen the cylinder no 1 is giving zero value.
i wonder how these measurements are made? are the injectors involved in that?
thanks
i wonder how these measurements are made? are the injectors involved in that?
thanks
MBWorld Fanatic!
Joined: May 2015
Posts: 4,037
Likes: 1,012
From: Miami, FL
2003 CL 600
That's impossible, the value is the actual RPM of the engine while cranking it for 6+ seconds during the test. If it was 0 it would mean it stopped turning?
Normally, you get one higher than the rest, due to lower compression and less resistance. The C class I just did today failed with 190ish on 2-4 and 450 on #1 cyl which has a damaged piston. A result of zero is impossible.
Normally, you get one higher than the rest, due to lower compression and less resistance. The C class I just did today failed with 190ish on 2-4 and 450 on #1 cyl which has a damaged piston. A result of zero is impossible.
Thread Starter
Member
Joined: Sep 2017
Posts: 173
Likes: 25
From: UK
Mercedes R320L CDI 4MATIC 2007
RE:
So if the battery is not charged enough the test can fail to complete? i noticed the voltage dropped quite low and the progress bar did not fill up completely. I assumed the test was stopping every time because of this cylinder giving zero value every time.
I will connect another battery to the one on the car for extra support and perform the test again. it is weird the car battery does not have enough of the power to run the test itself. maybe problem is the battery after all.
Thanks for your replies.
I will connect another battery to the one on the car for extra support and perform the test again. it is weird the car battery does not have enough of the power to run the test itself. maybe problem is the battery after all.
Thanks for your replies.
MBWorld Fanatic!
Joined: May 2015
Posts: 4,037
Likes: 1,012
From: Miami, FL
2003 CL 600
The instructions in SDS say to connect a charger to the car when using it, and it's quite important during tests like this, as weak voltage will result in slow cranking which can give false results.
