Alfa 159 diesel hard to start when cold

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Alfa 159 diesel hard to start when cold

Postby tangoman » Sat Dec 17, 2016 2:10 am

Gee its almost Christmas . but cars still play up . so was asked to have a look at a Alfa 159 diesel that was hard to start when cold . its summer over here in Australia so it does not get less then 24 deg c at night and most of the time it 30 deg c so its hot here . the work shop that give me the job just put in a set of glow plugs but the car was still hard to start when seating for more then a hour in fact it was so hard to start it would take more then 5 times on the auto start to get it going and was thinking this poor car will burn out the starter motor soon !! with lots of smoke when it starts up,. so I check with the scan tool first for any codes but it did not have any. so then I looked at the Injector correction and if you look at the photos you see they are not the best we had 3 in the negative this is no good because most off the time when I see this its a mechanical problem ! but we also had positive reading too 3.11 so this can be injectors no good . so its time to do some testing . I did a injector leak back test this was bad we do have bad injectors but this would not make the car hard to start when motor is cold with lots of smoke . if it was just the injectors we would have no smoke ! so need to do more tests . this time I did a relative compression see the photos . this was bad for the Alfa 159 we had 3 cylinders that was down this is why we had so much smoke when we start it up .. so this car needed injectors on the way out and a motor with 3 cylinders down !! The owner of the car is going to sell the car !! but this is why when we do tests on any car to make sure we look at the whole car system and not just scan the car or not just a back leak test because if we did not do the relative compression test we would have sold just the injectors and would have not fixed the car !! when the car did fire up and warmed it would had be hard to pick it had 3 cylinders down ! so make sure we always test all the tests before we make the call . and also the 3 cylinders that was down might have been for lots of carbon build up in the manifold or a intake runner broken and not letting air in but I did not go and further with more test because was told they going to sell the car !

wish you all the best for Christmas and happy testing to you all
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my set up
Attachments
Screenshot (132).png
The value of doing a relative compression with Picoscope on a diesel using no pressure sensors . just a current clamp fast and easy 3 cylinders down !
Screenshot (131).png
Scan data look at the Infector correction you can see the 3 cylinders in the negative this is most times a mechanical problem !
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The back leak test not the best
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getting ready to do the back leak test
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Getting my test equipment
tangoman
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