lightning

lightning

Well-Known Member
Could non-functional glow plugs cause white smoke (unburnt diesel) on startup?

l've noticed this recently on my TD5 Defender. However l've recently removed the glow plug relay next to the ECU because all four glow plugs are faulty.

When l tested them
Two were open circuit, one appeared to be short circuit and one showed a resistance of about 23K Ohms

So l removed the relay. l've got a new set to fit but haven't done it yet.
 
Last edited:
It is possibly unburnt diesel/low temperature in the combustion chamber, faulty glow plugs is a cause yes.
It could be air in the fuel lines, a leaky return line or low pressure (often caused by air in the lines).
Or it could be condensation.

Changing the heater plugs is a good start.
Let us know if it clears.
 
Unburnt fuel is usually dark smoke, black really.
White is tradionally head going. Hope its not that for you.
 
No, dark or black is to much fuel and or not enough air. Dark bluish is oil in combustion. Grey, partial burnt fuel and sign of low compression.
White smoke is usually unburnt diesel or can be water turning to steam.
As it clears soon after start up and if you are not loosing coolant then lack of glow on cold days is likely. I have similar issue with my car along with a bit of rough running until things warm up. When hot starting no smoke.
 
tottot said:
No, dark or black is to much fuel and or not enough air. Dark bluish is oil in combustion. Grey, partial burnt fuel and sign of low compression.
White smoke is usually unburnt diesel or can be water turning to steam.
As it clears soon after start up and if you are not loosing coolant then lack of glow on cold days is likely. I have similar issue with my car along with a bit of rough running until things warm up. When hot starting no smoke.
Click to expand...

So you mean yes then. Too much fuel and not enough air = unburnt fuel. Which is what I said.
White smoke could be water turning to steam was why I said a possible head problem, so again, Yes you agree.
 
Well, l will change the glow plugs and see how it goes, if it still smokes on startup then l'll need to get it looked at.
 
The place where the 5th glow plug would go is covered by the fuel pressure regulator. I also assumed it would have been cheaper to buy the glow plugs in multiples of 4 as that's the more usual engine size.

Yes, my TD5 sometimes puffs white smoke on start-up, especially when I go to Wales, as I leave the smallholding and chuff my way along the track back to the council maintained road. There's quite a steep hill immediately before I reach the tarmac and the acceleration needed to climb this always clears it. It's been doing this for about three years and hasn't got any worse. The MOT smoke test readings if anything seem to be getting better with age. The engine is still quite lively after nearly 150,000 miles. The only thing is that it is perhaps a little more 'clattery' than it was when I first got it at around 30,000. But otherwise it's fine.
 
l replaced the glow plugs and the white smoke on startup became black smoke!

Today l refitted my original ECU (after it failed last December l bought a replacement and kept the original as a spare after it was repaired)

The black smoke on startup has gone. So it must be something to do with the replacement ECU.
 
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