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Injector caused troubles

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Author Post
Tue Dec 17 2019, 09:13pm
Joined: Aug 29 2019
Member No: #4047
Location: Roskilde
Having solved the problem now, I'll share my experiences, should anyone else be so unfortunate, to end up in the same trouble.

I bought the car july 2019, outside temp 30-40 deg. and the car drove fine, only a very quietly "diesel knock" (I thought it was a valve tappet, at the time) at light throttle, and only sometimes.

Apart from glowplug trouble, pollution errors and limp mode, the car drove fine.. until mid september, when outside temp started to go below 20 deg.

It always drove fine when warming up, but when operating temp was reached, it started to cough and hesitate between 1500-2000 revs. and a very noticeable "diesel knock" would follow, it would get better and better as heat got into the engine, and after 1 hour of driving, it would almost be normal.

There were no error codes related to this issue, when checking with Diabox.

I measured all temp sensors I could find in Diabox, but all semed to give reasonable values, I even bought new lambda sensors, (Jaguar forum mentioned similar symptoms where lambda sensors was the culpit, and no error codes.) only to find out, that the 2,7 in our C6's only have exhaust temp sensors, and 4 of them. (2 pre-cat, 1 after rear cat, and 1 in DPF)

I also did some EGR testing/cleaning, since the EGR system should go into action, when operating temp are reached, but no difference, so eventually I blocked the EGR return pipes with 2 coins, (where you disconnect pipes from throttle body) but still no difference.

I did hovever see some diesel smoke at very light touch of the throttle, so that could only point at the injectors.

Around this time I had also read on some forum, (I was desperate, so search was quite wide: "HDI engine error") that injectors could be temp dependent.

I have no history of the injectors, but the car had only done 150.000 km, so I didn't expect them to be totally wasted.

First thing I learned was, that all returnpipe lock clips was installed from the wrong side, opposit the grove, it has to go into, (Yes I also had a return pipe comming off at the motorway due to this.) so apparently someone had been playing around with the injectors.

Looking at the picture, injector 3 and 4 seems to have seen quite more action than the rest, comparing the bottom part, and they are my main suspects, I first changed injectors in front, which cured most of the problem, and after the rear was changed, it was back to normal, and no more "diesel knock".
(I had earlier changed injector 2,5 and 6 in the pursue of the problem)

Since 6 new injectors is a small fortune, I had some weeks ago purchased 1 new and 5 used i god working order injectors, my plan was to have the new one as reference for correction numbers read out in Diabox, and return flow comparison.

I took one of the bad injectors apart, just out of curiosity, it seems it's all in the head, which raise the question: refurbished injectors, do they have the old head, or is that the part beeing "refurbished"/changed!?
Because that must be where the delicate pizo parts are located.

My old neighbor (works at a Citroen garage) said, that they change rather many injectors in the C3, they believe that heat kills the injectors.

I'm also quite confident, that the posts about engine noise, are down to worn injectors!

Sorry for the rather long post.

7 User said Thank You to Nikolaj for this Post :
 MGmike (17 December 2019) , 321dave (17 December 2019) , Hattershaun (18 December 2019) , cruiserphil (18 December 2019) , Eric (18 December 2019) , FraserG (18 December 2019) , keithc (19 December 2019)
Wed Dec 18 2019, 08:03am

Joined: Jan 24 2010
Member No: #38
Location: Celbridge
Hello Nikolaj,

Thank for posting this. Great post!

Phil C.
Wed Dec 18 2019, 10:14am
Joined: Aug 29 2019
Member No: #4047
Location: Roskilde
Thanks, sorry for the missing "b" in the headline.

Only good thing about nobody knowing about this problem, is that it apparently doesn't happen to often.

Another thing I forgot to mention, an easy test of probably bad injectors, with warm engine and in "Park", have a helper (my 10 year old son loved this job ) take the engine slowly up through the rev range, to at least 3000 rpm. and the look for any vibrations from the engine, there shouldn't be any, if the injectors are up to the job.

I had more vibrations than I was comfortable with, but with injector 3 and 4 being bad, that was to be expected.

I now see, that there actually was some signs pointing at the injectors from the beginning, always so easy to look back.
1 User said Thank You to Nikolaj for this Post :
 cruiserphil (18 December 2019)
Wed Dec 18 2019, 12:53pm

Joined: Oct 01 2009
Member No: #1
Location: Northumberland
Nikolaj wrote ...

Thanks, sorry for the missing "b" in the headline.

What missing 'B'
Wed Dec 18 2019, 01:57pm
Joined: Aug 29 2019
Member No: #4047
Location: Roskilde

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