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#1 cabcurtains

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Posted 05 January 2012 - 11:14 PM

This post is designed to give a basic overview of modern Toyota Diesel engines and their commonly troublesome components:

How does a Diesel engine work?
Firstly Diesel is not as flammable as Petrol. Diesel engines don’t have spark plugs to ignite the fuel, but to bring about combustion they require heat. If you put your finger over the end of a foot pump and pump it, your finger will become hot. This is due to compression of the air trapped inside the pump (the air molecules have less space to move about and collide with each other more frequently causing energy to be given off in the form of heat).
The same thing happens in a diesel engine: as the piston moves upwards, the air trapped inside is compressed, causing it to heat up (the temperature reached is circa 400 degrees C). Just before the piston reaches the top of its' stroke, the pump and injectors spray a very fine mist of diesel into the piston chamber. The intense heat of the trapped air in the piston causes the diesel to ignite, forcing the piston down and producing the power stroke which goes through the engine via the gearbox / wheels etc etc and off you go.

What are Glow Plugs?
When internal sensors detect that the core of the engine block has reached a certain designated temperature, or when a certain amount of time elapses, the glowplug relay switches off the "wait-to-start" light. A pre-heating cycle usually lasts for 2 to 5 seconds. The driver then turns the key to the "start" position. The glowplug relay switches off the glowplugs after the engine is running. In some newer cars, glow plugs continue to operate for up to 180 seconds after engine start to keep the engine within emissions regulations, as combustion efficiency is greatly reduced when the engine is very cold. Link http://en.wikipedia.org/wiki/Glowplug

As glow plugs wear out the vehicle will be more difficult to start, run poorly and produce a white/bluey smoke. Glow Plugs are a reasonably cheap to replace.

What is D4D?
D4D is Toyota’s version of Common Rail Diesel. The term "common rail" refers to the fact that all of the fuel injectors are supplied by a common fuel rail which is nothing more than a pressure accumulator where the fuel is stored at high pressure. This accumulator supplies multiple fuel injectors with high pressure fuel. Modern common rail systems, are governed by an engine control unit (ECU) which opens each injector electronically rather than mechanically.

What are Injectors?
Fuel injectors are a key part of modern automotive systems, as they're responsible for getting fuel into the engine in a precise, orderly and carefully engineered pattern. Unfortunately, the conditions we drive in are not ideal. Pollution is in the air, and fuel can be contaminated with water, dirt particles and other debris. Regularly changing your fuel filter (according to change interval in your service book) will help keep debris from circulating. You can also add fuel injector cleaner to your fuel tank, which may help solve running issues. Doing this at regular intervals of 10,000 miles or so might provide more cleansing than your engine actually needs, but it shouldn’t harm the system. Injector Cleaner can't improve your car beyond its original factory spec.

When injectors fail there are generally two approaches to repair, take the vehicle to a main dealer and have the whole set (£1000+) replaced or find a diesel specialist who may be able to replace or repair individual injectors (circa £250 each) after testing. Fuel Injector problem symptoms include, poor starting, rough running, loss of power, black or white smoke. It is generally known that injectors will need attention after 100,000 miles.

What is a Turbo?
Turbochargers are a type of forced induction system. They compress the air flowing into the engine. The advantage of compressing the air is that it lets the engine squeeze more air into a cylinder, and more air means that more fuel can be added. Therefore, you get more power from each explosion in each cylinder. A turbocharged engine produces more power overall than the same engine without the turbocharging.

When Turbo’s are failing they will typically cause the car to have a loss of power, excessive smoke and in some cases a high pitched whine. Turbo’s can often be repaired bya turbo specialists or replaced with a new unit, obviously a repair is cheaper.

What is an SCV?

SCV's (Suction Control Valves) are used in Common Rail diesel engines to control the pressure of the fuel in the accumulator. The pressure is varied by the ECU by controlling how much fuel the pump feeds into the accumulator, replacing the fuel as it is delivered into the engine by the injectors. Low pressure for the injectors at idle, high pressure at maximum power.

Electrically operated, SCVs can need to open and close at up to 200 times per second and if they stick or fail to open properly then poor running, starting and power loss can occur. Sticking when hot is often cited as a cause of hot starting problems. D4D pumps may have one or two of these valves depending on the type of pump fitted, this is important when ordering the correct parts.

Vehicles commonly affected by this have the 1CD-FTV 2.0 D4D Engine 2000-2005, found on RAV4/Avensis/Corolla built between these dates. This article SCV's on the RAV4 Forum provides an overview of the location and parts on a two valve pump. These parts are typically £250 to replace + fitting if required.

What is an EGR Valve?
Exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in modern engines, EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. After a while the gases containing dirty, sooty carbons start to cover and coat the intake area and valves causing the air to fuel ratio to become unbalanced thus resulting in more black smoke being emitted from the exhaust. This black smoke is then drawn back into the air intake via the EGR valve. A vicious cycle then starts with the engine producing more smoke and sootier carbons being drawn into the intake, a major problem.

Symptoms of EGR issues include lack of power, engine hesitancy and then a surge of power followed by black sooty smoke. A fall in fuel economy may also occur. On most Toyota engines the valve is easily removed and cleaned, a dealer will charge an hours labour to do the same job. If the valve fails it will cost around £300 to be supplied and fitted by Mr T. If the vehicle is used continually then carbon clogging could eventually lead to head gasket failure on AD engines, please review the attached document to see if your car has one of these engines.Attached File  AD Head Gaskets.pdf   46.17KB   3905 downloads

A simple method of trying to keep the EGR valve clean is to drive the vehicle (once warm) hard by bringing the revs near to the red line, this will result in black soot leaving the exhaust, continue this until the soot no longer appears. This should be a weekly event. This is also known as an Italian Tune Up.

Personally as my 2.2 D4D Verso is out of warranty i clean the EGR every 10k, this a superb guide http://www.toyotaown...howtopic=106241

What is D-Cat?
D-CAT (Diesel Clean Advanced Technology) is Toyota’s version of a diesel particulate filter (DPF) which is a device designed to remove soot from the exhaust gas of a diesel engine. The soot created by the engine is burnt off during the regeneration process, this process uses fuel which is added by an additional injector, this additional fuel usage reduces MPG when compared with vehicles that dont have a DPF. The regeneration process occurs at road speeds higher than can generally be attained during urban usage ,vehicles driven exclusively at low speeds in urban traffic will require periodic trips at higher speeds to clean out the DPF.

On cars with a very high sixth gear the engine revs may be too low to generate sufficient exhaust temperature for regeneration. Occasional harder driving in lower gears should be sufficient to burn off the soot in such cases. With this type of DPF regeneration will be initiated by the ECU every 300 miles or so depending on vehicle use and will take 10 to 15 minutes at 40MPH+ to complete. You shouldn't notice anything other than perhaps a puff of white smoke from the exhaust when the process is completed.

If the DPF doesn’t regenerate properly eventually a warning light will be displayed and the vehicle should be taken to a main dealer. Continued usage past this point may destroy the DPF completely so it must be replaced, this will be very expensive (£1000+).

DPF Continued

If your car is type approved and registered after the date below it will have a DPF to meet the EU Emissions, things can get very complicated here. Vehicles are often built long before being registered, so you could purchase a 2010 car that was a 2009 model. Its important to ask what model year your car is and which emission standard it meets. Its possible to be driving a 10/60 or even an 11 Reg thats not Euro 5 (V) if the car was built long before being registered.

Euro 5 (V) Emissions Standard Commenced - September 2009

If you only drive low mileages in town do not buy a Diesel with a DPF. A Petrol is more suitable.

Modern Diesels are very complex machines, following manufacturer servicing guidelines is essential as is using the correct oils, fluids and drivers checking levels frequently.

The issues mentioned above are not restricted to Toyota's, all manufacturers have these issues and probably more of them.

Hopefully this is useful to people :thumbsup:

Please PM me if any of this requires amending.

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#2 Heidfirst

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Posted 06 January 2012 - 09:46 AM

:thumbsup:
candidate for a sticky imo.
You might want to explain/mention that the DPF works by injecting diesel into it as fuel to burn off the deposits & that therefore vehicles equipped with DPF get noticeably worse mpg than an equivalent without.

#3 Mistermena

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Posted 06 January 2012 - 10:15 AM

This post is designed to give a basic overview of modern Toyota Diesel engines and their commonly troublesome components:

How does a Diesel engine work?
Diesel unlike Petrol is not flammable but rather combustible (under extreme pressure it will combust). Diesel engines don’t have spark plugs to ignite the fuel, but to bring about combustion they require heat. If you put your finger over the end of a foot pump and pump it, your finger will become hot. This is due to compression of the air trapped inside the pump (the air molecules have less space to move about and collide with each other more frequently causing energy to be given off in the form of heat).
The same thing happens in a diesel engine: as the piston moves upwards, the air trapped inside is compressed, causing it to heat up (the temperature reached is circa 400 degrees C). Just before the piston reaches the top of its' stroke, the pump and injectors spray a very fine mist of diesel into the piston chamber. The intense heat of the trapped air in the piston causes the diesel to ignite, forcing the piston down and producing the power stroke which goes through the engine via the gearbox / wheels etc etc and off you go.

What are Glow Plugs?
When internal sensors detect that the core of the engine block has reached a certain designated temperature, or when a certain amount of time elapses, the glowplug relay switches off the "wait-to-start" light. A pre-heating cycle usually lasts for 2 to 5 seconds. The driver then turns the key to the "start" position. The glowplug relay switches off the glowplugs after the engine is running. In some newer cars, glow plugs continue to operate for up to 180 seconds after engine start to keep the engine within emissions regulations, as combustion efficiency is greatly reduced when the engine is very cold.

As glow plugs wear out the vehicle will be more difficult to start, run poorly and produce white smoke. Glow Plugs are a reasonably cheap to replace.

What is D4D?
D4D is Toyota’s version of Common Rail Diesel. The term "common rail" refers to the fact that all of the fuel injectors are supplied by a common fuel rail which is nothing more than a pressure accumulator where the fuel is stored at high pressure. This accumulator supplies multiple fuel injectors with high pressure fuel. Modern common rail systems, are governed by an engine control unit (ECU) which opens each injector electronically rather than mechanically.

What are Injectors?
Fuel injectors are a key part of modern automotive systems, as they're responsible for getting fuel into the engine in a precise, orderly and carefully engineered pattern. Unfortunately, the conditions we drive in are not ideal. Pollution is in the air, and fuel can be contaminated with water, dirt particles and other debris. Regularly changing your fuel filter (according to change interval in your service book) will help keep debris from circulating. You can also add fuel injector cleaner to your fuel tank, which may help solve running issues. Doing this at regular intervals of 10,000 miles or so might provide more cleansing than your engine actually needs, but it shouldn’t harm the system. Injector Cleaner can't improve your car beyond its original factory spec.

When injectors fail there are generally two approaches to repair, take the vehicle to a main dealer and have the whole set (£1000+) replaced or find a diesel specialist who may be able to replace or repair individual injectors (circa £250 each) after testing. Fuel Injector problem symptoms include, poor starting, rough running, loss of power, black or white smoke. It is generally known that injectors will need attention after 100,000 miles.

What is a Turbo?
Turbochargers are a type of forced induction system. They compress the air flowing into the engine. The advantage of compressing the air is that it lets the engine squeeze more air into a cylinder, and more air means that more fuel can be added. Therefore, you get more power from each explosion in each cylinder. A turbocharged engine produces more power overall than the same engine without the turbocharging.

When Turbo’s are failing they will typically cause the car to have a loss of power, excessive smoke and in some cases a high pitched whine. Turbo’s can often be repaired bya turbo specialists or replaced with a new unit, obviously a repair is cheaper.

What is an EGR Valve?
Exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in modern engines, EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. After a while the gases containing dirty, sooty carbons start to cover and coat the intake area and valves causing the air to fuel ratio to become unbalanced thus resulting in more black smoke being emitted from the exhaust. This black smoke is then drawn back into the air intake via the EGR valve. A vicious cycle then starts with the engine producing more smoke and sootier carbons being drawn into the intake, a major problem.

Symptoms of EGR issues include lack of power, engine hesitancy and then a surge of power followed by black sooty smoke. A fall in fuel economy may also occur. On most Toyota engines the valve is easily removed and cleaned, a dealer will charge an hours labour to do the same job. If the valve fails it will cost around £300 to be supplied and fitted by Mr T. If the vehicle is used continually then carbon clogging can eventually lead to scoring of the pistons which could lead to head gasket failure.

A simple method of EGR cleaning is to drive the vehicle (once warm) hard by bringing the revs near to the red line, this will result in black soot leaving the exhaust, continue this until the soot no longer appears. This should be a weekly event. This is also known as an Italian Tune Up.

What is D-Cat?
D-CAT (Diesel Clean Advanced Technology) is Toyota’s version of a diesel particulate filter (DPF) which is a device designed to remove soot from the exhaust gas of a diesel engine. The soot created by the engine is burnt off during the regeneration process, this process uses fuel which is added by an additional injector, this additional fuel usage reduces MPG when compared with vehicles that dont have a DPF. The regeneration process occurs at road speeds higher than can generally be attained during urban usage ,vehicles driven exclusively at low speeds in urban traffic will require periodic trips at higher speeds to clean out the DPF.

On cars with a very high sixth gear the engine revs may be too low to generate sufficient exhaust temperature for regeneration. Occasional harder driving in lower gears should be sufficient to burn off the soot in such cases. With this type of DPF regeneration will be initiated by the ECU every 300 miles or so depending on vehicle use and will take 10 to 15 minutes at 40MPH+ to complete. You shouldn't notice anything other than perhaps a puff of white smoke from the exhaust when the process is completed.

If the DPF doesn’t regenerate properly eventually a warning light will be displayed and the vehicle should be taken to a main dealer. Continued usage past this point may destroy the DPF completely so it must be replaced, this will be very expensive (£1000+).

If you only drive low mileages in town do not buy a Diesel with a DPF. A Petrol is more suitable.

Modern Diesels are very complex machines, following manufacturer servicing guidelines is essential as is using the correct oils, fluids and drivers checking levels frequently.

The issues mentioned above are not restricted to Toyota's, all manufacturers have these issues and probably more of them.

Hopefully this is useful to people :thumbsup:

Please PM me if any of this requires amending.


Fantastic post my mate! :thumbsup: Should be a Pinned one I recon to :toast:

#4 Jamesbelfast

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Posted 06 January 2012 - 12:44 PM

A good write-up summarising many aspects.

Just to clarify one point can you explain the relationship regarding..........carbon clogging can eventually lead to scoring of the pistons which could lead to head gasket failure?

#5 cabcurtains

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Posted 06 January 2012 - 01:22 PM

Heidifirst - I've made a couple of changes :thumbsup:

Mr M - I would like this pinned as it took me ages! :help:

James - This is the only point i don’t have the absolute answer for so i have reworded the text, if you do or anyone else has let me know and i will add it. However i want to keep it simple as best possible or people won’t read it :)

#6 BALIKBAYAN

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Posted 06 January 2012 - 03:06 PM

Good post. I hope it will get pinned.
But there is something I feel is not very accurate though. It is this section: [How does a Diesel engine work?
Diesel unlike Petrol is not flammable but rather combustible (under extreme pressure it will combust).}

First of all diesel is flammable, but it needs to reach around 55-60 degrees C first to leave flammable vapour, petrol has flammable vapour from around -20 degrees C. Maybe you should write that diesel is not as flammable as petrol is, instead of that diesel is not flammable.
Diesel will not combust under extreme pressure. If that was true you would have a combustion in the high pressure pipes on a diesel engine and not in the cylinder. Normal dieselengines like a Scania or Volvo has an opening pressure at the nozzle around 250-300 bar. And it is still diesel in fluid that is in the system. The compression in the cylinder makes the cylinder warm and it is that temperature that ignite the very small drops (mist/spray) of diesel that is injected in the cylinder just before TDC.
How you would rewrite this later section I don't know, but it was totaly wrong as you wrote it, but you meant the right thing. I hope you will not get angry with my small corrections.

#7 dervdave

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Posted 06 January 2012 - 03:42 PM

Excellent informative post that will help many



#8 cabcurtains

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Posted 06 January 2012 - 03:50 PM

Balikbayan - Slight tweak made, i am very angry now, only kidding :lol: I dont want to make this over technical or people will switch off :yawn:

Dave - Cheers :)

#9 Jamesbelfast

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Posted 06 January 2012 - 04:12 PM

The definition between flammable and combustable depends on the flash point of each material. This is purely for classification purposes only.
For liquids the term flammable is for liquids which have a flash point of 65.5 degreees Centigrade (100 F) or higher.
For comparison the flash pount of petrol is around minus 45 C whereas for diesel the figure is plus 100 C. So technically the original quote is correct.
Theoretically any combustable material can be burnt in a compression ignition engine designed to suit. For instance there are engines out there running on wood smoke.

When it comes to scored pistons or cylinders it is usually caused by the lubrication oil becoming over-loaded with hardened carbon particles which have caused a break-through of the oil filter or have blocked the oil control rings on the pistons.

#10 BALIKBAYAN

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Posted 06 January 2012 - 05:33 PM

I might be wrong about the flashpoint of petrol. It might be another thing that has flashpoint around - 20 degrees C. It might be the dangerousclass or something like that. I am very sure about the flashpoint of diesel fuel,though. I should be as I work as marineengineer on a ship. There are lot of different dieselfuels and every fuelquality has different flashpoints. Dieselfuels for cars has a min limit of around 55 degrees C. Dieselfuels to use on ships has a min limit of 60 degrees C, limit for armed forces in Sweden. I also had a look at the TDS(technical data sheet) of Shell's low sulphuric diesel for the UK market. You can find it at shells webpage. There they state that the flashpoint minlimit is 55 degrees C and typical flashpoint for their diesel is 60 degrees C.
To be classified as flammable the liquid must have a flashpoint below 65 degrees C. If the flashpoint is higher it is classified as combustible. You can all double check it att wikipedia.
I am sorry if I go too deep in the technical stuff and maybe a bit off topic too. But I don't like when someone say that I am wrong when I know that I am not wrong.

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