2.7 CRD low power, smoking - any ideas?
 

I have a 2004 2.7 CRD WJ. Runs fine, but I'm having these problems:

Once started the engine occasionally "twitches" for 30-60 seconds at idle, and smoking white, even more if given some revs. Then, after the engine warms up, the ticking sound appears somewhere in the top of the engine. It ticks for a while, then suddenly disappears for a few seconds, then appears for a minute or two, and so on.. (it's irregular). And that ticking never goes away when engine is hot. When the engine is hot, I get no "twitching" and the smoke is gone at idle, but if given some revs it still smokes white (not as bad as cold though).

I'm thinking maybe it's sucking air in the fuel somewhere? I see no leaks on the fuel lines. I ordered some OEM Mercedes fuel line O-rings and will try to replace those to see if there's any difference. Next thing would probably be taking the fuel injectors out for testing/reconditioning..

Any other common problems to look for, or anyone having a similar problem?

Some other info:
- The turbo has been rebuild at a specialized shop (so not oil getting to the exhaust)
- Engine Oil pressure is fine, so I'd like to think it's not the lifters ticking..
- Engine Oil level is not decreasing, so probably not worn piston rings etc.
- Coolant level is not decreasing, so that's eliminated too.

While black is usually overfueling, white smoke is usually completely unburnt fuel. If it does it mostly from cold then glow plugs could be the culprit. Not sure if the 2.7 still glows a bit when warm, some diesels do. It could also be leaky injectors if we are looking for a cause of too much fuel that is not burning. Air is less likely but can relate to the poor running but I would think any decent air leak would cause hard starting. Ticking could be the onset of Black Death if the injector seats have not been done. You could check this visually or feel above the injectors for any spray or air when it's happening. Mine also ticks but I'm pretty sure it's from the viscous heater pump as it's very rhythmic and goes away when warm. I replaced all the front pulley bearings so I can only assume it's inside the pump but all still works fine.

You could also have an issue with the high pressure pump again too much fuel but this is less likely as the pressure regulator and sensor should have reacted by now

Orings are a good cheap thing to ensure they are correct but I'm not sure will be the cause. Id be

Checking for codes (do the 3 time key jiggle)
Testing glow plugs and/or glow plug relay/circuit
Testing injectors for leak back. Kits available on eBay or get 5 vegemite jars and make your own

You can throw a complete air in lines check before this of course because it's cheap. Check clear lines, replace all the black fuel hose with clear hose and run for a day or do to check properly if there are any leaks before the filter but do not leave the cheap clear stuff in for too long. Again though not sure this is issue but low cost to test.

A video of start up with sound could help, say 1 minute or so.

When you say twitching, does this mean a rough idle?

If so like Fester I'd be inclined to check the glow plugs first, easy to do with a multimeter. All you need to do is disconnect the power connector and measure the resistance, they should all be very similar if they are good, if you have one or two with a significantly different resistance value, this is a likely culprit.

Air in the fuel line typically results in hard starting, and you don't mention any starting difficulties. It is a good thing to replace the orings as they will eventually create problems but I don't think it is the primary issue you are seeing.

FWIW, mine also has a bit of a tick too.

mine has a tick, always has......white smoke I'd go for raw fuel so you may have an injector thats knackered, leaking fuel . After a run is your exhaust black and moist or black and dry, thats a good run to get everything hot.
A small bit of air in lines won't cause any problems but a fair bit they are hard to start or won't, mine has had a pea size bubble in the line for years and I've given up with it.
Is the top of your injectors clean metal or a bit mucky ??

Thanks for all the tips guys, I'll be checking those and upload a video later today.

I forgot to mention these things in my first post:

- No, there is no black death, and I've checked with spraying soapy water around them, no compression leaks. Although, when I bought the car, the insulation foam was melted underneath the plastic engine cover and made a bit of mess on engine top - I wonder where the heat came from to cause that melting, maybe the leaky injector seals, so not sure if the previous owner did something with them - if they are old injectors, maybe they're shot?

- No trouble codes, except for one Transmission fault which is unrelated.

- Starting is a bit funny actually, it usually starts after a few cranks, then the short period of rough idle, then all ok. But if the car has been sitting say for a whole week, it takes a lot more cranks to start and sometimes after starting it cuts out immediately, then, after a second attempt - a few cranks and start ok. This is why I'm thinking it maybe slowly sucking in air somewhere...

- My viscous heater pump is a bit tired too, when revving to 3500-4000rpm it starts to "whine", but other than that I don't think it makes any sounds on idle. I'm pretty sure that ticking comes from the top of the engine.

New O rings for sure and follow festers post to try to isolate the air leak but I think you may find the O ring will cure the starting though if still there it probably points to the HP pump playing up, you may have a number of issues which will have to be overcome but start with the inexpensive ones first. Just be gentle with the fuel line clips they will probably crumble in your hands, other threads cover this in detail, ....

I believe that my friend is a sign of past black death, or at least black serious injury seeing as it appears to have been dealt with. A good reason to ditch the cover entirely to keep an eye on things. You could also look under the plastic wiper cowl and see if an access hole has been cut, that would tell you if rear injectors have ever been replaced and hopefully they did all of them.

your newly divulged starting issues certainly sound like air but the white smoke is a separate issue still.

what do you define as a few cranks, mine starts without any discernible delay or cranking eg within say 2 seconds cold or hot one day or a few. Even having sat for 6 odd months it only cranked for a few seconds. There is no reason they should not start almost instantly if everything is good. Poor starting of course could still be glow plugs but not the stalling then starting fine.