Citroen Xantia starting badly with white smoke, troubleshoot

[Skatsani]

Hello,
So I have a Citroen Xantia 1996 1.9 SD diesiel. The problem is that the engine starts badly:
It‘s not the ignition, as the engine „starts up“ fast. But the rpm is very low and it seems like a few cilinders are not working as they should, because the engine does this psch psch psch sound and shakes and vibrates a lot, the whole car starts shaking. There is some smoke from exhaust and it‘s mostly white/grey. The most interesting part is that I might wait like 5 minutes until the engine starts running smoothly on its own, or I can press just hold the engine at max rpm for a few seconds (5-10) and the engine will start working way better if not ideally. It is not dependant on temperature because in winter and in summer the same thing happens. One thought was that there might be air leakage, but I checked the tube running from the filter to the engine and there was no air (there is to be until I changed the filter and also fixed a leak in that pear shaped pump).
Does anyone have some ideas what could be the problem? As I was kind of dissapointed when the filter and the pump leakeage did not help.
Any ideas appreciated.

[CitroJim]

Welcome to the forum

White/grey smoke on startup is indicative of unburned fuel and definitely not a lack of it! That it starts OK might rule out the classic cause which is duff glowplugs but I would check that all the glowplugs are good and functional as a first step. If you have no record of them being changed then change them for good new ones and ensure they are the correct type for your engine.

Yours, being an SD, may need a different sort from the standard TD as does the normally aspirated diesels. I know from experience that the wrong glowplugs can make a big difference.

If the engine continues to run badly when it is hot and the situation does not fully resolve then it will most likely not be glowplugs as they only affect the first few minutes of running.

Air leaks it definitely is not due again to the presence of white/grey smoke indicating plenty of fuel being present.

If glowplugs do not give a full cure then the engine may be a little low on compression on one or more cylinders. It is unusual but not unknown. One easily checked cause can be very tight valve clearances although again if it is tight valve clearances it tends to cause hard starting and almost instantly cures once the engine is just a little warm and is worse in winter then summer. This is due to an XUD quirk where the valve clearances are tightest when the engine is stone-cold and they expand and open up as the engine warms.

Yet another cause can be a severe restriction on the inlet side causing a very restricted airflow into the engine. The cause of this can range from a clogged air filter, holes in the turbo piping to a seized turbo.

A potential cause can be incorrect diesel injection pump timing. If it is too retarded there can be lots of smoke and poor running. This is indicated by the engine running very quietly with a tendency to overheat, readily smoke, be reluctant to rev and develop little power. Has there been anything done to the pump recently that may affect its timing settings? Normally though, a badly retarded pump makes starting hard too...

On a related point, has the cambelt been replaced or disturbed recently? If the static cambelt timing is just half a tooth out it can give rise to this sort of problem.

If all else fails to find a solution, a leakdown test will be needed to check the compressions are in order.

All a little odd but I hope the above may help throw some light on a potential cause.