Smoke on cold start - bear with me while I explain my reasoning..

300tdi defender - on cold start, I get smoke from the exhaust - more than it used to. Starting is perfect.
I need to start it against a white background to accurately see the colour.

The smoke is fairly dark, and lessens as it warms up to a stage where it only smokes black on hard acceleration (or when booted in too high a gear in front of a convertible with the top down....)

My first thought was tappets - checked and two were slightly slack on the gap so adjusted these. That rules them out as the cause.

Its ready for an oil change - that will be done this weekend. On checking the oil, it was a little above maximum (I don't remember it being like that). This lead me to thinking 'diesel in oil' . I can't find a reliable home test for this, so I will make sure that the oil is spot on the max when its changed.

I have thoughts now as to the cause of the smoke.

1. valve stem seals leaking - this would cause blue smoke and fairly quickly clear wouldn't it?

2. dribbly injectors after stopping vehicle? Is this even a thing? blacker smoke, also clearing quickly ?

As to the possibly higher oil level - can dribbly injectors cause this? Fuel into a stationary bore could seep pass the rings? Second though on this is a leaking diaphragm in the lift pump - I will take the fuel filter off to make sure its full.

Thoughts please - I know its an age old problem.....

You say it is dark smoke and can only be seen against a white background, for a 300tdi that does sound pretty normal particularly at this time of the year with colder temperatures, most will smoke quite a big puff of black smoke on startup then will be grey whispy smoke until warmed up as the diesel burn is not complete. Mine is rather clean actually, it's got about 150,000 miles on it, I have reconditioned the head and it only really smokes when booted in too high a gear, but at this time of the year it will puff a small amount of smoke until warmed up - then it is crystal clear.

I would try and identify the smoke colour and smell, blue smoke with some cold diesel burn grey smoke can look quite dark.

I would say probably no to 1. but don't rule it out entirely at this point. 1 doesn't necessarily create blue smoke because if they are leaking it is usually the exhaust valves to leak first, the oil will therefore run down the valve and coat it, a drop or two may make it into the cylinder but on startup it will get sort of vaporised and smoked out with heat rather than an oil burn from a hot engine that is actually consuming the oil, it tends to be a light gray and can create a lot of it, as for how long it takes to clear, depends on severity, it also depends on how it is driven, if you let it coast along on overrun it can draw more in so first time you step on it after overrun it will smoke again creating a pretty cool 007 smoke-screen.

Almost certainly no to 2. because 2. would cause other issues during warmed up engine and running if the injectors were so shot they were dribbling diesel when the engine was off. If the injectors were so leaky as to pour diesel into your engine and increase the engine oil level you would have starting trouble, you don't mention this. Also really the engine would run rough and very smokey... it could be a lazy injector or blocked, but the beginnings of one really if it clears when warm.

Think simple first, air filter clean? Turbo OK? Air pipework OK? Diesel OK - bad batches are common enough - could the smoke in fact be water? How old is the timing belt? The timing does vary overtime slightly which can cause smoke. Is it just old and cold and the combustion is not great until warmed up?

Thanks for all that - useful stuff, well explained

oil change saturday - i will also check the air filter and diesel filter.

Timing belt was done last year - I loved th cover away recently to check for fluff and oil and it looked okay. I do intend to lock it all up and make sure the pump is set correctly, as it wasn't't me that set the timing

I'll try and get the smoke on video against a white background too

cheers!

steveo said:

Thanks for all that - useful stuff, well explained

oil change saturday - i will also check the air filter and diesel filter.

Timing belt was done last year - I loved th cover away recently to check for fluff and oil and it looked okay. I do intend to lock it all up and make sure the pump is set correctly, as it wasn't't me that set the timing

I'll try and get the smoke on video against a white background too

cheers!

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If you suspect the timing you can do it in about 5 minutes with some drill bits, 2 sockets and a ratchet.

Pop a drill in that fits snugly, take note of size. Then I would try advancing it a tiny bit in your situation. So to advance it you want the pump flange to be ahead of the sprocket to do that you would loosen the sprocket to flange bolts, then with a 22mm (I think it is) socket you would turn the pump ahead a little, you can do this simply by using a slightly bigger or smaller drill say 0.25mm of a difference to enable you to move the pump and sprocket independently a prescribed amount.

I would need to have it in front of me as it's been over a year since I tweaked mine but I think as you advance the pump the gap will get smaller, so a 0.25mm smaller drill bit than originally used could be inserted then give the pump flange (on the 22mm socket) a tap clockwise, the flange will close in on the smaller drill thus giving you a measured movement. I always tweak my timing to get it bang on, factory set (which is what the pin holes are for) is just that, factory set, spending the time to tune these properly can make a big difference.

Sounds normal.
Smokes on start up and runs clean, can i have one.

discomania said:

If you suspect the timing you can do it in about 5 minutes with some drill bits, 2 sockets and a ratchet.

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Any need to lock the crankshaft as if I was doing the belt, or just rotate the engine until I can get the drill bit in the pump hole?

Has your injection pump been fiddled with ?

Sounds exactly like my 200tdi. If this is a new development, then something has changed, and worn valve stem seals will certainly give you more burnt engine oil at startup. I should add that after an oil change, my startup smoke colour changes to grey, as it's burning off lovely new oil!

steveo said:

Any need to lock the crankshaft as if I was doing the belt, or just rotate the engine until I can get the drill bit in the pump hole?

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You don't need to lock the engine at all, you only need to pin between the pump flange and the sprocket. I would as a matter of course set the engine to TDC first. When you do it the sprocket will be held by the timing belt against the cam/crank so it is not going anywhere, so all you are moving is the pump, if you cock it all up all you need to do is bang a timing pin back in and line it all up and you are back to factory set. There is no need to be scared here, just get in amongst it. The only time I would not mess with timing is where I think it is so damn good that I suspect messing with it will cause a negative impact. The difference can be phenomenal, I am talking about power increases, reduced smoke and smoother engines as a result of tiny changes here. My 300tdi went from very tractory to a much smoother, cleaner, more efficient machine after about 15 minutes of tweaks the first time I did it. The previous owner had just left it at factory set. I did the timing belt again last year and twiddled with the timing afterwards to get it spot on.

Also, always do it on a very warm, ideally hot engine and take it for a spin each time, there is no point having it tuned a treat for cold running - so you may have to do this over a couple of days to check for the cold smoke changes you are looking for. Bear in mind you may not even cure this if something else is worn/faulty, but always a good Saturday afternoon or Friday summer evening job to see what you could have from your engine.

tottot said:

Has your injection pump been fiddled with ?

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My frst thought to

tottot said:

Has your injection pump been fiddled with ?

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yes it has - but that was two years ago.... the cold start smoke is new

steveo said:

yes it has - but that was two years ago.... the cold start smoke is new

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I'd change the oil. If the colour of the cold start smoke changes to grey, it's engine oil = valve stem oil seals

Grey is diesel, blue is engine oil

Kev12 said:

Grey is diesel, blue is engine oil

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There are variations to this in all honestly, it is usually used as a start point in trying to guide unaware people through fault finding, it has always been the loose rule but in practise it is not always strictly in accordance. The more you learn about a given topic, the more you will discover there are actually many variations and caveats to the facts, I call it the "Law of diminishing falsehood".

Oil smoke in valve stem issues tends to create a grey smoke - read my earlier reply which explains the smoke generation from valve stem oil leaks.

I understand your point, I was just over simplifying it as OP says the oil level hasn't dropped and we still don't know what colour the smoke is

And here's the OP

Well, last few days, its behaved itself - usual puff of dirty smoke on startup, then runs pretty clear. I'm wondering if thats because its a bit warmer outside. I can't think that .05mm adjustment on two tappets can make a difference.

Oil change is tomorrow, and as I have access to a ramp I will be dropping the sump to reseal it as I have a leak from there.

Its never needed any significant top ups of oil between changes (done every 6 months) using Total 15w40 semi synth.

so today saw the sump removed - glad to see no gunge in there, and the strainer filter was clear also. No obvious contamination of the oil.

In terms of startup smoke, its looking good, and running quieter too. I wonder if the low temperatures of late had deteriorated the oil ? Its bang on time for the oil change at 6 months.

Thanks for all the advice - if it keeps behaving I may have a pump tweak soon