Non starting Disco 3

Can anyone here tell me why a Disco 3 with knackered glow plugs will not start once temp goes below 0.
Last year it would be OK as long as not below -4. I use the trick of removing the engine cover and pouring boiling water over the grey temp sensor, starts straight away. My 1998 Isuzu pickup starts without leaving glow plugs on at -5. Surely this engine should not need glow plugs at -4? My friends old Peugeot 2.7 coupe that has the same engine starts straight away. What is it with the Land Rover system? Not worth changing the glow plugs, at 156000 miles I expect big problems.

How's the battery? Is it cranking the engine over at the correct speed? If the engine isn't spinning fast enough to generate sufficient compression heat, then it won't start quickly.
Are you allowing plenty of time for it to fire? Or just stabbing at the starter in short bursts.

New battery last year as we thought that was the problem. No short bursts ans she turns over plenty fast enough. The glow plugs need replacing but that really is not the problem. At only minus 1 a modern engine with modern diesel should not need glow plugs. It seems it`s to do with the temp sensor as if you pour boiling water over this it stars straight away. Look it up on You Tube. I am NOT an idiot. I was an apprentice Cat fitter in the 60`s. Too old now but I could still strip and rebuild and MGB with my eyes shut but no longer interested. I just find it rather stupid that this trick works and nobody seems to be able to by pass the engine management. I am told this sensor manages the fuel system depending on temperature.

There's more to this, than failed glow plugs.

The TDV6 doesn't or shouldn't need glow plugs to start from cold, unless it's below -5° or so, but even then it would start eventually, as the combustion chamber warms up.

What if you unplug the coolant temperature sensor?
This will put the engine in a limited operating strategy, which I think will set the fueling for the engine at 60° or so. It'll also put the gauge at max, and flash an over temperature warning on the LCD. But if its a cold engine fueling issue, this should prove it.

I tried that as I also saw a post on another forum that suggested that, or even putting a paper clip between the contacts. It seemed to work once but I think that was a fluke. It still does not explain why pouring boiling water over the sensor works? I am amazed that a modern car will not start at minus 1 or 2. It is getting fuel, take a look at You Tube Land Rover Discovery 3 Cold Start Solution. Luckily enough it is an easy way to get her to start but this is a bad design somewhere that this little sensor can cause so many problems. As I have said my friends older Peugeot Coupe with the same engine stars first time with no waiting for the glow plugs to heat up at all. Plus the fact the glow plugs pack up and are seized in is bat design.
Thanks for taking an interest. I love this car, most comfortable thing I have ever driven but sadly still British Management can`t build reliable cars. As always cut corners and costs and blame the guys who build them.

Do you think it`s worth buying a new sensor and just wrapping it up well? £27 has to be cheaper than trying to drill out and replace the glow plugs, that will cost around a thousand pounds unless it goes wrong and engine out job?

Worth checking your engine oil temp sensor as this can give problems with cold starting.

The coolant sensor is not faulty. It's poor engine management having crap injector strategies at low engine temps, pouring hot water on the sensor makes the car think the engine isn't stone cold.

Thanks for that. It has been suggested I make sure the fuel filter has been changed. The car is regularly serviced so I am going to check and maybe get both changed.

Some people have added a resistor in the coolant sensor wiring with a switch in the cabin, flick switch start engine then flick switch off again.

You might find your friends frenchie has a different management system, ie as soon as they unlock the car the glowplugs may have already started to heat even before the key is in the ignition? so it may appear they dont need to glow it, but it has already started the prcess unbeknown to them.
Some of the french cars had quite clever glowplug control set ups.

If the car has plenty of power when running then the fuel filter is most likely okay.

My 56 plate struggles when it gets under -5C so I got a cheap remote module off ebay to fire up the webasto heater to preheat the coolant. Run the heater while I'm having a shower in the morning and it fires up instantly.

The glowplugs are supposed to be easier to remove on the eu4 engines but its still not something I'm gonna try!

TheMunster said:

My 56 plate struggles when it gets under -5C so I got a cheap remote module off ebay to fire up the webasto heater to preheat the coolant. Run the heater while I'm having a shower in the morning and it fires up instantly.

The glowplugs are supposed to be easier to remove on the eu4 engines but its still not something I'm gonna try!

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Mine would not start this morning at minus 3, wondered why then saw the temp gauge was at cold, some plonker hdd forgotten to trun the webasto timer on!
10 seconds on glow plugs and we were away.

I use it every morning now even when its not that cold, only have a short run (7 mile) to work so helps the engine get warmer quicker.

Mine will go in the cold but it takes a bit of cranking.

TheMunster said:

I use it every morning now even when its not that cold, only have a short run (7 mile) to work so helps the engine get warmer quicker.

Mine will go in the cold but it takes a bit of cranking.

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5 miles for me, poor thing!

Wiltys said:

tried that as I also saw a post on another forum that suggested that, or even putting a paper clip between the contacts. It seemed to work once but I think that was a fluke.

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It should work all the time, as it alters the fueling strategy, just enough to allow the engine to fire.

Wiltys said:

It still does not explain why pouring boiling water over the sensor works?

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Again, the boiling water trick alters the fueling strategy just enough, for the engine to fire.

Wiltys said:

Do you think it`s worth buying a new sensor and just wrapping it up well? £27 has to be cheaper than trying to drill out and replace the glow plugs

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All sensors have a manufacturing tolerance, which means a replacement could fix the issue. It could also not fix the issue, but you won't know unless you swap it.
It might be prudent to change the oil temperature sensor too, just in case.

Mine never failed to start, no matter how cold it was, and mine had duff plugs, with more miles on it too.

Wiltys said:

but sadly still British Management can`t build reliable cars

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Technically the engine is French, and the management system is German. There isn't much on the D3 that is actually English, although it was developed and assembled in the UK.

Thanks for all the replies. I`m sure with all this info I can get it sorted.

Forgot to add. I was not going to replace the sensor. Just by a new one, wrap it in pipe insulation and connect that up. It will not tell me if I have a overheating problem but might save pouring boiling water over the one still fitted just while the weather is so cold.

P.S. Again. Anyone know if there is any one near Bath that can fit a remote for the Webasto fuel heater?

The fbh remote is a pretty simple install iv built and fitted loads, you can buy them ready to from the bay or disco3forum

Thanks.