E300 Turbodiesel mystery
Discussion
Not the usual sort of question in this particular forum I know, but as it's a Mercedes issue anyway, I thought I'd ask! 
One morning on startup I noticed an initial lumpiness accompanied by quite a bit of "diesel knock" followed by a puff of blue smoke after start.
Easy diagnosis, a glow plug had gone and this was confirmed by the glow plug light coming back on again for about a minute after start up.
Having had the car from new (nearly 16 years ago) I knew that changing all of the glow plugs was the way to go as unless it turned out to be the one in No. 1 cylinder right at the front, the inlet manifold had to be removed to access all the other five. So I had all 6 glow plugs replaced (apparently 2 were unserviceable) and collected the car later that day (while still warm).
The next morning on start-up, there was still a slight roughness for a second or two accompanmied by some diesel knock and just a very little smoke. However, now the glowplug light remained out after start up suggesting that all glow plugs were working.
I returned to the garage asking whether there were different specifications g/plugs, wondering whether for example they had fitted a "40 watt bulb" where a "60 watt" was required. My thinking was that such a scenario would complete the circuit so preventing the waring light from relighting after start up, yet the actual plugs themselves (or one of them) wouldn't be producing sufficient warmth during the time it was on for the fuel to ingnite efficiently at first.
I was told that if the light remains out after start up then forget about the glowplugs as they must all be OK and think about one of the injectors being a bit clogged/dirty and not giving an even spray at the outset when cold. I was advised to run a bottle of diesel injector cleaner through with half a tank of diesel (I used Shell V- Power for this). But really it's made no difference and as the issue seems proportional to the outside air temperature each morning and the coincidence with the glow plug replacements, I'm back to believeing thaat the problem still lies with the glow plugs. By the way, the battery is fine with good output.
Does anyone have a suggestion or know a good diesel specialist in the Herts/North London area. I've not got a lot of time as I'm due to take the car on a 4 week trip through Europe for work in the coming days.
One morning on startup I noticed an initial lumpiness accompanied by quite a bit of "diesel knock" followed by a puff of blue smoke after start.
Easy diagnosis, a glow plug had gone and this was confirmed by the glow plug light coming back on again for about a minute after start up.
Having had the car from new (nearly 16 years ago) I knew that changing all of the glow plugs was the way to go as unless it turned out to be the one in No. 1 cylinder right at the front, the inlet manifold had to be removed to access all the other five. So I had all 6 glow plugs replaced (apparently 2 were unserviceable) and collected the car later that day (while still warm).
The next morning on start-up, there was still a slight roughness for a second or two accompanmied by some diesel knock and just a very little smoke. However, now the glowplug light remained out after start up suggesting that all glow plugs were working.
I returned to the garage asking whether there were different specifications g/plugs, wondering whether for example they had fitted a "40 watt bulb" where a "60 watt" was required. My thinking was that such a scenario would complete the circuit so preventing the waring light from relighting after start up, yet the actual plugs themselves (or one of them) wouldn't be producing sufficient warmth during the time it was on for the fuel to ingnite efficiently at first.
I was told that if the light remains out after start up then forget about the glowplugs as they must all be OK and think about one of the injectors being a bit clogged/dirty and not giving an even spray at the outset when cold. I was advised to run a bottle of diesel injector cleaner through with half a tank of diesel (I used Shell V- Power for this). But really it's made no difference and as the issue seems proportional to the outside air temperature each morning and the coincidence with the glow plug replacements, I'm back to believeing thaat the problem still lies with the glow plugs. By the way, the battery is fine with good output.
Does anyone have a suggestion or know a good diesel specialist in the Herts/North London area. I've not got a lot of time as I'm due to take the car on a 4 week trip through Europe for work in the coming days.
tobinen said:
Sounds injector related and not glow plugs IMO. There was an MB specialist in Letchworth whose name escapes me at the moment, or try Wayne Gates in Harrow if not too far away.
Thanks and yes, I think it was injector related. Just had all 6 injectors cleaned and new nozzles fitted. This had started a new issue.... A loud top end rattle at idle or just above which reading through several forums COULD be the MAF sensor. Tomorrow will be the first cold start since the injector overhaul, so I don't even know whether the original problem described above has been resolved!!!!HI, Can I recommend you purchase one of Peter Russek's manuals from a well known internet auction site.I have found the book invaluable and will save me £££'s I can now get handy with the spanners with confidence when I need too. I am not affiliated with the author in anyway and other manuals are available. :-).Even if you only use it for your own diagnostics.
Thank you both for your responses and I will certainly look for that manual right now.
I've had all 6 injectors "serviced", new nozzels fitted and combution chambers cleaned and tightened. New fuel filter at the same time. Turned out 4 nozzels were leaking/dripping and three were "not delivering properly".
This has cured the diesel knock and any smoke on start up from cold (or after a longish period of inactivity) which is now perfect. But it's introduced a low speed diesel knock instead
The combined wisdom of three garages (one in which I have high confidence) is that after a few hundred miles this will likely just disappear once the new injectors have settled in and any tiny amounts of air that may have entered the system have purged their way out. We shall see!
This new 'knock' is only at low revs and only when the engine is fuelling, not on the over-run or when accelerating above about 1500 RPM.
I have about 900 miles to do in the next few days, mostly motorway so if it hasn't quietened down as predicted then I will be in the south of Spain where the local M.B. Concessionaire for that coast is in my opinion, as good as it gets.
I've had all 6 injectors "serviced", new nozzels fitted and combution chambers cleaned and tightened. New fuel filter at the same time. Turned out 4 nozzels were leaking/dripping and three were "not delivering properly".
This has cured the diesel knock and any smoke on start up from cold (or after a longish period of inactivity) which is now perfect. But it's introduced a low speed diesel knock instead
The combined wisdom of three garages (one in which I have high confidence) is that after a few hundred miles this will likely just disappear once the new injectors have settled in and any tiny amounts of air that may have entered the system have purged their way out. We shall see! This new 'knock' is only at low revs and only when the engine is fuelling, not on the over-run or when accelerating above about 1500 RPM.
I have about 900 miles to do in the next few days, mostly motorway so if it hasn't quietened down as predicted then I will be in the south of Spain where the local M.B. Concessionaire for that coast is in my opinion, as good as it gets.
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