Renault Megane strange engine...

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Renault Megane strange engine...

Postby victor2k » Thu Oct 19, 2017 11:32 pm

Hello,
Today I made some tests on a 2007 Renault Megane 1.5 DCI with the bad starting,white smoke and knocking at cold engine.
The readed faults was related to cyl 4 (at the limit of compensation ) and A/C but the engine was warm(75^C),no white smoke and knocking.
Measuring the compression on cyl 1(my fault :D ) I captured a strange pressure variation in cylinder...I blame the injector for a too late injection but some other advices are wellcome.
Also I can't add new custom probes ...v 6.13.1 crashed again and again when I tried to add a new accelerometer. :?
Thank you.
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Renault_Megane_Diesel_20171020-0001.psdata
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Re: Renault Megane strange engine...

Postby ben.martins » Mon Oct 23, 2017 1:13 pm

Hi Victor,

Thank you for your post. I've had a chance to look at your capture and I believe what we are seeing is the effects of diesel in the cylinder. Whilst I can't be 100% sure, we have seen this splitting of the tower when the injector has been left connected whilst carrying out a compression test using WPS. However, we would normally expect to see a significant increase in cylinder pressure which isn't there on your one. Please see attached image for something we have seen before.

I would just like to confirm that when you carried out the test you did have all the injectors disconnected? If I assume you have and going by the symptoms you have listed it may be that the injector isn't fully closing and therefore allowing some fuel to enter the cylinder. As we approach peak compression this amount of fuel could ignite and cause this anomaly in the waveform and the white smoke and knocking you are getting.

I know the Renault injectors are notorious for being difficult to remove so I might suggest leak of check to see if you have an injector that isn't returning as much fuel as the others before going to any real extremes.

Hope this helps and do please keep us updated with how your getting on.

Kind regards

Ben
Attachments
Diesel incylinder compression.jpg
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Re: Renault Megane strange engine...

Postby Tronic » Mon Oct 23, 2017 2:35 pm

HI Victor!

That capture looks pretty much like the one I had when a glow plug washer did not seal. It was not that pronounced as in your capture though – it was just a small dip at back of the compression tower. I still have the capture in one of our PC’s, I can search for it if you would like to see. Sadly, all injectors where bad on this engine and the customer did not want go further. It was a Renault with K9K-702 1.5DCI engine.

Regards

Bjorn
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Re: Renault Megane strange engine...

Postby victor2k » Mon Oct 23, 2017 4:54 pm

Hello,
My capture must reveal a abnormal working of injectors(knocking,white smoke) so the injectors was connected.Of course the capture was made at idle :D trying to protect the pressure sensor and hose .
I will make a new capture with the injectors disconnected.
What I see in my attached file :if the main injection is increased with a 20-25%(490us vs 413 us,570us vs 490us)then I have a second pressure peak at 20-23* ATDC(and not at 10*ATDC where the pressure peak is expected),descreasing main injection at the following injections I have only one peak-something like ECU test the limit of injectors...I will attach the file from the repaired injector.
Thank you for your support.
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New folder.rar
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20171019_185025.jpg
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