Corsa cdti. - diesel low compression

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Wed 2 Jun 2010 01:50
Corsa cdti. - diesel low compression - CorsaPita

I am having problems with my corsa cdti (Bad Black smoke and poor throttle responce) there is no engine lights coming up so i have been looking at mechanical problems. (checked all the inlet pipes for blockages,swapped all the fuel system and sensors no fault codes coming up)

I did a Compression test when the car first started playing up and blowing large quantites of black smoke out, that came back as 350psi per pot, with the compression being close to the 400psi target figure i thought it was low as it was cold and hadn't been run for a bit.

Skipping on it has been getting harder to get started but the smoke is about the same, i have been trying it for a week or so and yesterday i retested the Compression to find all 4 bores have dropped down to between 220 and 240psi.

The thing that confuses me a bit is why all the cylinders are low fairly evenly? i know the car has had a head gasket in the recent past, i decided today to take the head off as i thought the gasket could have gone?? thing is the Head bolts where not very tight, the head its self looked like the dowl had not been lined up properly before tightening so there was a big gouge with a nasty bur, the head gasket its self looks like a cheap/poor quality one and last but not least, i cleaned the head up and removed the bur then put the head on the block without the gasket between, i then put pressure on the head to see if it felt a good mating surface (which it wasn't) i could rock the Head on the block (not much i admit but it wouldn't grip a pice of paper i put under the corner) so the head is warped.

Thing is i'm not sure if this would cause my symptoms? surly a engine that is designed to run at 400psi compression at 350 should run ok? maybe just harder to start? but i wouldn't expect large amounts of Black smoke? What sort of loss in compression would you see problems? Also do you think its a coinicedence that there is head problems and there is another problem lurking?

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Wed 2 Jun 2010 08:42
Corsa cdti. - diesel low compression - oilrag

Hi Corsapita,

I notice that you have four threads running on what looks to be the same basic problems. It might be better for continuity to ask the Mod`s to make them into one - and then keep `bumping` that thread up as time goes by.

Good luck with the engine.

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Wed 2 Jun 2010 15:18
Corsa cdti. - diesel low compression - Peter.N.

If there is enough compression for the engine to start I would hardly think it would cause black smoke. If its running very rich through lack of air, the diesel fuel could well be running down the bores and washing the lube oil off, that could account for your lack of compression. It certainly sounds as though it needs a new gasket and the head machined, us a steel laminated gasket, they are much tougher.

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Wed 2 Jun 2010 16:18
Corsa cdti. - diesel low compression - oilrag

I was reading through one of the earlier threads about it not wanting to rev over 3,000 rev s. That sounds like it`s in limp mode. Has it had a full diagnostic test on the Dealer equipment?

I wonder if something was disturbed when you had that head gasket done?

It`s a very odd reading situation reading of how it wasn`t started for 6 months (if I have it right) after the headgasket being done.

Problem is that it`s been pulled apart so much now that it`s possible that new faults have been introduced.

It sounds like that on a personal level it`s going to be best to put it through auction.

I`m not a tech, by the way.

Good luck with it.

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Wed 2 Jun 2010 18:14
Corsa cdti. - diesel low compression - CorsaPita

I think the main problem was that it wasn't used for so long after the head was done.... The people of course don't want to know, I don't know if the problem is there doing or some thing stuck or failed due to being stood??? But all said and done they must have driven it deliver it back and the way it runs at the moment some one would have called 999 thinking the car was on fire....... I am gutted i didn't try it round the block when it came back but the place i was working for was heading down the toilet and i was working all hours, unfortunatly the car was the last thing on my mind.

The reving over 3k is kind of fixed now, i found quite a bit of oil in the Turbo so i replaced it with a good second hand one and the throttle responce is still slow but it will rev all the way up the range now.

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Wed 2 Jun 2010 18:27
Corsa cdti. - diesel low compression - CorsaPita

TBH i'm not sure if thats possable, the pistons have a bath in the center where all the liquid fuel collects, before i pulled the head off i tried to get some engine oil down the bore to try and do a wet compression test (had to poke a tube through the inlet valve to get oil down the side of the bore). I can't garantee i didn't just pore the oil into the baths in the center but i did all four in the same manner so you would expect one of them to show diffrent readings?

i

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Fri 4 Jun 2010 18:18
Corsa cdti. - diesel low compression - CorsaPita

Well bit of an Update, I have put the head back together and its hitting 390psi pot pot Cold so i'm happy with that, problem is Its still smoking badly but now it looks more grey than black but about half the Quantity of the black before? I do have an issue to fix with the injector not sealing at the base (think it just needs new Copper washers as it blows past quite bad but at least it shows i have good compression)

Also the engine management light has come on (well it resets after 5 mins of battery off then pops back on 2 seconds after starting) but as these things go my Opcom tool has decided to play up now (Won't read the ECU and clicks Rapidly) its lucky i have another corsa here i know is working well as i would be trying to buy an ECU right now if i hadn't tried it on another car.

I am really happy with the compression though. It even sounds different when i turn it over. I think i'm getting there even though its still playing up, when i get my Fault code reader fixed . I'll see whats playing up, i may even drop the fuel and put some fresh stuff in (its old and has loads of redex in it that won't help)

Edited by Avant on 05/06/2010 at 12:12

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Fri 4 Jun 2010 18:56
Corsa cdti. - diesel low compression - oilrag

How are you managing to swap ECU`s between cars to try them? I thought they had to be coded to the system, so they would work with the other ECU`s in the Can-Bus system?

Well, something like that.. ;-)

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Fri 4 Jun 2010 19:15
Corsa cdti. - diesel low compression - CorsaPita

Sorry i haven't swapped the ECU over yet, i have been doing some reading up on that and it would seem it ECU is coded (its writen on the front of it) once that has been changed/reflashed you have to program the Transponders etc

Its not and easy job thats why i've left it until last.

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Sat 5 Jun 2010 11:15
Corsa cdti. - diesel low compression - piston power

Have you checked the turbo seals? how is the impeller blades any play?

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Sat 5 Jun 2010 13:24
Corsa cdti. - diesel low compression - CorsaPita

Yes, there was oil in some of the Inlet pipes and i couldn't decide if it had come from the Turbo of Breathers? so i took the Turbo off and there was a fair amount of oil just say in the Compressor housing so i swapped the turbo for a Good second hand one but it was still blowing smoke out (maybe a little less)

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Mon 14 Jun 2010 19:56
Corsa cdti. - diesel low compression - quandoe

dont know if this is of interest but vauxhall apparently has an issue with cdti coolant sensors and wiring... there is a mod kit which includes new gold plated contacts and a new sensor... this is giving a fault normally of poor starting when cold due to the ecu getting a false reading and shortening the lengh of time an injector is open and the length of time the g/plugs operate... but this could also cause the opposite fault where by if the ecu thinks the engine is cold then the injectors are open for longer pumping to much diesel into the cylinders and causing excess smoke, simular to the choke being stuck-on on a petrol engine... due to the wrong burn ration you would also experience a lack in power.

a simple check is to see if the coolant sensor plug has gold coloured contacts

sorry i dont have part numbers but i just thought it might help and give people another avenue to look at

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