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Author Topic: Diesel in the Snow  (Read 10865 times)

Offline stokeballoon

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Re: Diesel in the Snow
« Reply #10 on: 22 December 2010, 08:27 »
Are any Diesels owners having problems with waxing? 

My Missus's A3 TDi had a problem the other day, left the car warm up as the day warmed up, and no further problems.  It causes rough running, non starting etc.

It is caused where the diesel started to solidify (freeze) at very low temps.

UK Diesel is rated to -15 degrees. 
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Offline Agreeable Slick

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Re: Diesel in the Snow
« Reply #11 on: 22 December 2010, 08:30 »
The only reason that the diesel would freeze is if it had excessive amounts of water in it.

Where do you fill up from? I would suggest changing suppliers for the time being if it's beginning to solidify.

Also it would be worth whipping the fuel filter out and removing the housing it is in as well, to ensure that the water drain off paths are clear and empty. I'm not sure if the A3 has a WIF (water in fuel) sensor in the system, but worth checking out.
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Offline stokeballoon

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Re: Diesel in the Snow
« Reply #12 on: 22 December 2010, 08:45 »
Cheers,

RAC blokey reckoned it was 'waxing', temp was about minus daft at the time.  It is a fairly new 59 plate 170 Tdi
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Offline ajmoir36

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Re: Diesel in the Snow
« Reply #13 on: 22 December 2010, 09:13 »
No waxing here, although mine lives in a garage most of the time, probably doesnt get as cold.
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Offline Rhyso

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Re: Diesel in the Snow
« Reply #14 on: 22 December 2010, 09:56 »
Does this make it extremely difficult to start first thing? I've noticed that mine really struggles if its been sat for more than a day.  The Golf was never as difficult to start  :undecided:

Got a new fuel filter to chuck in.  Would that help?  :undecided:
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Offline Agreeable Slick

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Re: Diesel in the Snow
« Reply #15 on: 22 December 2010, 10:04 »
What you have to remember is that your injectors are machined in such a way that they have between 5-8 holes and they are microns in size, through which you are trying to force diesel through, at start up, at probably 200BAR (increasing as load/speed does).

There is also a large dead volume initially in the rail, pump housing, and fuel lines, that you are trying to pull/push towards the injectors. Also there is a very cold combustion chamber to heat (via glow plugs at first) and then cold air being used (which diesels dislike at the best of times). Add that to the huge inertia that the diesel has requiring to be turned and it all adds up.

Basically, cold weather = harder for a diesel to achieve first fire.
« Last Edit: 22 December 2010, 10:17 by Agreeable Slick »
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Offline Rhyso

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Re: Diesel in the Snow
« Reply #16 on: 22 December 2010, 10:12 »
Quote from: Agreeable Slick on 22 December 2010, 10:04
What you have to remember is that your injectors are machined in such a way that they have between 5-8 holes and they are microns in size, through which you are trying to force diesel through, at start up, probably 200BAR (increasing as load/speed does).

There is also a large dead volume initially in the rail, pump housing, and fuel lines, that you are trying to pull/push towards the injectors. Also there is a very cold combustion chamber to heat (via glow plugs at first) and then cold air being used (which diesels dislike at the best of times). Add that to the huge inertia that the diesel has requiring to be turned and it all adds up.

Basically, cold weather = harder for a diesel to achieve first fire.

Cheers for that  :nerd:

Just been a little bit shocked at a supposedly 'better / newer engine' being much harder to start  :sad: 
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Offline Agreeable Slick

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Re: Diesel in the Snow
« Reply #17 on: 22 December 2010, 10:17 »
The main problem is that once the engine is off the pressure in the system slowly falls away, like everything pressure related it is practically impossible to keep the pressure constant over a long period of time when there is a flow path avaliable to it.

So the pressure in the rail will be maintained for a short period (hence stop start diesel cars are able to operate) but once turned off for the night the pressure will fall to zero gradually. When you turn on again on a sub zero morning the pump needs to get fuel moving from the tank to the engine through tiny diameter pipes. It's worth remembering that the pump is engine driven as well, so it will only operate at turn over speed until combustion starts. :nerd:
« Last Edit: 22 December 2010, 10:18 by Agreeable Slick »
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Offline Steve30

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Re: Diesel in the Snow
« Reply #18 on: 22 December 2010, 17:40 »
Quote from: Agreeable Slick on 22 December 2010, 10:04
What you have to remember is that your injectors are machined in such a way that they have between 5-8 holes and they are microns in size, through which you are trying to force diesel through, at start up, at probably 200BAR (increasing as load/speed does).

There is also a large dead volume initially in the rail, pump housing, and fuel lines, that you are trying to pull/push towards the injectors. Also there is a very cold combustion chamber to heat (via glow plugs at first) and then cold air being used (which diesels dislike at the best of times). Add that to the huge inertia that the diesel has requiring to be turned and it all adds up.

Basically, cold weather = harder for a diesel to achieve first fire.
Nice post Slick , that explanes it now for mine why its difficult starting when its really cold.  :wink:
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Offline The Doc

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Re: Diesel in the Snow
« Reply #19 on: 22 December 2010, 18:49 »
I've had no problems starting the golf coldest has been -17
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