T

thetim

Well-Known Member
300tdi. Smoked a lot. Reset the timing. Cleaned right up. Six months later, smokes a lot. Black smoke, i.e. incomplete combustion.
And I mean a lot. Big puff of smoke on starting (always starts first time, mind) and if I a) boot the throttle when the turbo's not boosting, or b) really boot it under any conditions, turbo on boost or not, the road behind disappears in a black cloud. I'm driving gently because it's antisocially bad otherwise.

My first thought is that the pump timing's drifting off. Is it possible for the pump timing to move without the valve timing also going, or am I one tooth from disaster?

Any other thoughts? I've checked the boost hoses and they're all in good condition internally, so I don't think they're collapsing. Fuel consumption isn't obviously ludicrous, running temps seem normal, air filter's clean.
 
black smoke is too much fuel too little air, check tappets settings, induction side from filter to manifold and then injectors
 
Filter to manifold is clear - I've taken all the hoses off to check. I haven't checked the tappets though. On the basis that it cleaned up totally when I did the timing, I wondered whether it was the right amount of fuel being injected too late for complete combustion. I agree injectors are another potential culprit but didn't want to wade in and change them if something else was to blame.
 
thetim said:
Filter to manifold is clear - I've taken all the hoses off to check. I haven't checked the tappets though. On the basis that it cleaned up totally when I did the timing, I wondered whether it was the right amount of fuel being injected too late for complete combustion. I agree injectors are another potential culprit but didn't want to wade in and change them if something else was to blame.
Click to expand...
im not saying its not possible you have to have a very open mind when trying to sort problems but usually poor timing gives a whiter smoke
 
Thankyou - that's useful. The injectors may well have 180,000 miles on them. Couldn't hurt to look at the tappets - one job I've never done.
 
Have you also looked at the pump 'tuning'? i.e. the boost pin position, star wheel position and 'smoke screw' position?
 
No - when I acquired it and it smoked, I assumed that the pump had been turned up (there was a big "no smoke, no poke" sticker on the back) but never got round to backing the fuelling off again. Then I changed the timing belt and the smoke disappeared completely. That's why I'm surprised, and a bit suspicious, that the smoke has returned steadily over the last six months or so. I'm expecting the effects to be related but am struggling for ways to link it all together. Could it be explained by not tightening the fuel pump pulley sufficiently, or am I flogging a dead horse in suspecting a timing issue?
 
thetim said:
No - when I acquired it and it smoked, I assumed that the pump had been turned up (there was a big "no smoke, no poke" sticker on the back) but never got round to backing the fuelling off again. Then I changed the timing belt and the smoke disappeared completely. That's why I'm surprised, and a bit suspicious, that the smoke has returned steadily over the last six months or so. I'm expecting the effects to be related but am struggling for ways to link it all together. Could it be explained by not tightening the fuel pump pulley sufficiently, or am I flogging a dead horse in suspecting a timing issue?
Click to expand...

Yes. As said, black smoke is too much fuel too little air.
 
Had to take the accessory belt off for another job today so checked pump timing - it's spot on, so evidently the fault does lie elsewhere.
 
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