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Discussion Starter #1
Hi all.
I have a Laguna II 1.9dci 2002 model tourer which has done about 140k miles.

I have a very smokey diesel which failed the MOT and I have posted a few threads regarding this.

I have gone through everything, new Turbo, new EGR, Timing checked etc, new cat, intercooler removed and checked, boost pipes checked for tears etc...

The car drives very well and starts on the button all the time..

I have just recently done a compression test and found that No 1 Cylinder was 7 bar, no 2 was 6 bar, no 3 was 6 bar and no 4 was 7 bar.. These seem very low for a diesel and as the compression ratio is very low would this cause incorrect combustion causing the black smoke..

Possibly the valves are not sealing properly but would it be an idea to do the rings aswell???

hope someone can help

Cheers
 

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The compression test figures are miles too low - according to the Haynes manual thye should be 19-1 which is 19 bar - are you using the correct type of compresson tester. Low compression on a diesel will result in fuel remaining unburnt which causes a smokey exhaust and excessive fuel consumption. It's highly unlikely there could be burnt valves in each cylinder - but you couldn't find out exactly without removing the cylinder head. Have the compression figures double checked cos if the figures you say are correct I'm surprised its running at all.:)
P.S. The figures you quote would even be poor for a petrol engine
 

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Discussion Starter #5
Thanks for all your replies.

Firstly the car doesn't burn any oil. The oil level is fine and I don't get blue smoke just the black smoke..

When I done the compression test I used the wrong card to print them on. The actual readings are

Cylinder 1: 15 bar
Cylinder 2: 13.5 Bar
Cylinder 3: 15 bar
Cylinder 4: 13.7 Bar

These figures seem high enough to run the engine as the engine seems to run perfectly, but they are a bit off the 19 bar mark...

If I took the head off to check and redo the valves would it be worth doing the rings also...?

Cheers
 

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Hi Merky - that sounds better - no engine especially a worn one never makes the full specified compresion figures - it may be worth checking the valve timing because if it was out one tooth on the timing it could still run but like a dog. Start with checking the timing - also may be worth another visit to a diesel expert before you start to strip the engine:)
 

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Discussion Starter #7
Hi
I have checked this already, I locked the crank and checked the camdshaft and is spot on..

The engine runs lovely not like a dog as you've said thats why this is baffling me a bit. The only next thing is injectors, maybe overfueling??? and then head off. Its driving me mad.
 

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Hi Merky - I suggest you get the pressure being delivered by the high pressure fuel pump tested and then maybe move onto injectors - could also be the fuel pressure regulating valve.:)
 

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Discussion Starter #9
Hi all.
I have just had delivered the proper compression tester adapter to fit into the glow plug hole. I carried out the test again and the results are as follows

Cylinder 1: 30 bar
Cylinder 2: 31 bar
Cylinder 3: 30 bar
Cylinder 4: 31 bar

The needle on the meter goes up very quickly to suggest the rings are in top order and the valves are sealing as they should... No need to overhaul then????

I will check the pressure in the high pressure pump as soon as I can get hold of the equipment and I will let you know

Cheers
 

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Discussion Starter #10
Hi all.
Has anyone ever checked the high pressure circuit of the fuel system as the pressure can reach about 1200 bar I am unable to fine a pressure tester that goes this high..

If the high pressure pump was at fault would this really cause my heavy smoke problem as if the pressure was low then the car would not start or rum correctly..

If the pressure was to high then the regulator should adjust this surely, but then the regulator could be fault. Is the 3 pin plug the regulator???

Thanks
 

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Hi Mercky - very few bits of everyday test equipment would be capable if working at the high pressure you refer to but what is more important is the pressure actually in the rail and going to the injectors. According to the Haynes manual the fuel pressure regulator is at the back of the pump and is connected by 2 cables - also you may need to check the fuel pressure sensor (fed by 3 cables) which is located on the common rail. Unfortunately the book doesn't give a wiring diagram or colours for the cables. It is possible the injectors themselves are faulty and may be dripping fuel when not required - a good diesel specialist company should be able to bench test them for you.
Good luck and keep us posted.:)
 

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They are very low, I have just tested my scenic dci as I have problems with no power, I have 1 pot that is down to 20 bar, the others are 40 bar so I am now considering removing the head and trying to investigate the problem.
 
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