After idling for a long time white smoke/misfire

d215yq

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Hi all, is this normal on an old IDI diesel? I haven't been able to drive it more than round a field where I park for the last 7 weeks and even that is illegal so I have just been driving in 1st gear 50m to check it all still moves and then letting it idle for 20 minutes to warm up and charge the battery every 2-3 weeks.

It's been fine but this time (3rd time) it all started fine and then after 1 minute of idling started misfiring almost stalling with white smoke. I revved it a bit to 2k rpm (didn't want to attract attention for more) and then it was fine.

Is this sort of thing usual for a diesel that has had a total of 1h idling without being driven properly/warmed up properly for a while? I tend to remember the only time it did something similar was just after passing the MOT emission test, but as we do a DIY drive through MOT here that would have similarly been 30 minutes of non stop idle also. Other than this it never ever really does city or traffic driving so probably has idled more this 7 weeks than it normally does in a year...

I'm not sure why it would do this, does half burnt fuel build up in the cylinder and the affect combustion aversely? Can I put it down as likely to be fixed automatically whenever it's able to be driven properly again, or should I be usign the cuarantine period to investigate more?
 

Rappey69

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Mine idled for nearly 8 hrs to keep me warm some years ago when i was gridlocked and stuck in snow. when i finally got going there was no smoke and car ran fine.
 

Doug1234

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You did not mention glow plug light coming back on so its most likely got some air in the fuel lines so once you start up its got to draw fresh fuel through, lack of fuel will cause white smoke.
Check the small pre filter just to see if any junk in it ( they always have a large bubble of air in them so don't worry about that ) but its most likely just because it has been sat and the smallest of leaks that would never ever cause a problem has over the weeks just let a bit of air into fuel system and let fuel creep back a bit to fuel tank.
Once you get back to normal I wouldn't expect it to be an issue.
 
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d215yq

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You did not mention glow plug light coming back on so its most likely got some air in the fuel lines so once you start up its got to draw fresh fuel through, lack of fuel will cause white smoke.
Check the small pre filter just to see if any junk in it ( they always have a large bubble of air in them so don't worry about that ) but its most likely just because it has been sat and the smallest of leaks that would never ever cause a problem has over the weeks just let a bit of air into fuel system and let fuel creep back a bit to fuel tank.
Once you get back to normal I wouldn't expect it to be an issue.

Thanks, would that be accompanied by some slight diesel leak too? I replaced all the hoses and pre filter last year as they were leaking and haven't spotted anything since then, though in the tray i did notice a bit of yellowy green fluid just now for the first time since replacing them. I suppose that fits in with your theory of a slow leak in that it normally never builds up in any meaningful quantity being driven every 2 or 3 days but this time it has had 7 weeks to build up? I'll check all the hoses for leaks anyway in case it is something obvious.

As for the glowplug light it's never worked and (with a multimeter) only 4 out of 6 of the plugs have the correct resistance and the other two are open circuit. This is fine for starting above 20 degrees C and needs a few seconds of accelerator at start up for below then. It started at -2 degrees this winter without the other two and only ran rough for 5 seconds so i haven't bothered thinking of replacing them - they're the two that are hard to get to which is probably why they weren't changed before. My thoughts would be a glowplug issue would mean it misfires at start up, not fires up fine and idles fine and then a minute later starts to misfire?
 
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d215yq

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Are you running any veggie oil or is it pure diesel?

I have ran it on up to 40/60 veg oil but last put veggie oil in November 6 tankfuls ago, so it must be nearly 100% pump diesel.
 
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d215yq

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I have never found a problem changing glow plugs on your model ,if the engine is warmed up first.

Well I can't get to the last two without taking the manifold and other bits off which is probably at the limit of my skill level, and something i wouldn't do while it's still running OK. If it broke completely I'd give it a go but it seems a lot i could mess up while it works. It's also worth noting that it starts perfectly fine with 15-20 degrees C + which is March to December here, so it is not the same as if I lived in the UK...

Also it got skimmed when I did the head gasket/valve stems and they told me as part of their diagnostics when they were doing all this 5 years ago that the compression after putting it together was very high for an engine of that miles and that means that it will start even cold easily. To be honest I'm not sure how much of that was true or just to make me feel better about paying the 900€ bill but it might explain it...
 
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d215yq

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Just as an update, we've been free to move around our province in the last week and I've done 600 miles, after first 30 motorway miles the car notably ran a lot smoother at lower rpm, probably just wasn't used to not being driven anywhere and just idling to keep the battery charged for 8 weeks. The undertray is also completely dry so whatever oil/diesel leaked in the 8 weeks must have been a very very slow leak as it's impersceptible when just left 2 days between drives. No visible smoke at idle now either

Happy to be able to drive to the countryside and walk freely (well actually here it is legal to drive to restaurants/hotels/tourist establishments but weirdly it is illegal to stop and go for a hike outside one's own town - but I'm happy to ignore that rule as it's stupid). Just got to fix the passenger electric window which I can't think how to do as it's stuck up and designed to come apart down - Other than to destroy the regulator in situ which looks like a right pain and easy way to cut my hand. In the grand scheme of things it's not important - for the time being I'm not allowed a front seat passenger anyway (the rules state people from other households have to sit on different rows to maximise distancing so they're in the back!)
 
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