Diesel Injector & Pump Repair FAQs

Stuck Bosch Common Rail Injector, how do I remove it?cross graphic

Instructions to remove Bosch Common Rail injectors fitted to a Mercedes.

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Blow-by or the Black Death, what is it all about?cross graphic

Injector "blow-by" can be the cause of some of the following symptoms.

  • Hard or difficult starting
  • Erratic or uneven tick over or idle
  • Lumpy running
  • Smoke on tick over or acceleration
  • Black tar around the injectors and a chuffing sound from the engine when running

Injector blow-by occurs when the injector does not seal against the injector seat in the cylinder head. Often a chuffing sound is heard or black "tar" can be seen around the injectors. The engine could also experience one or more of the above symptoms. On some engine applications if this continues serious engine damage could result due to the fact that the ECU will over compensate the fuelling on the cylinder or cylinders with the seating problem causing piston washing or cylinder over fuelling. Even if the injector is removed, cleaned, a new copper washer fitted and then replaced it will not always rectify the problem as the escaping combustion gases may have eroded the seat in the cylinder head. The seat in the cylinder head will need to be refaced with a seat-cutting tool.

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Can a diesel engine run on fuel other than diesel?cross graphic

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EN 590 DIESEL-SURE TEST KIT Patent pending

The short answer to this question is yes. A diesel engine burns fuel without a spark by injecting an exact amount of fuel into a cylinder containing air that is made hot enough to burn the fuel by compression alone. Hence diesel engines fall into the family of compression ignition engines as apposed to spark ignition engines. Provided the fuel will burn at the temperature created by compression, the engine will run. History shows that diesel engines have been manipulated to run on a variety of substances including sunflower oil, coconut oil, cottonseed oil, buttermilk, turpentine and paraffin. Nevertheless, these products may cause harmful long-term effects including the formation of carbon deposits and excessive wear, leading to eventual failure of fuel injection system.

Can the EN 590 DIESEL-SURE test guarantee that the fuel contains no paraffin or heating oil?cross graphic

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EN 590 DIESEL-SURE TEST KIT Patent pending

No. The EN 590 DIESEL-SURE test is designed to identify fuel that does not conform to the current European Standard EN 590 for diesel fuel. Refineries throughout the world do cut diesel with small proportions of paraffin to improve winter flow properties. However, the product sold as diesel must still conform to specification.

 

DPF Cleaning, which method is best?cross graphic

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See the attached document showing the comparison between our DPF Flash Cleaner Machine on the other most common DPF cleaning methods.

Our technology is different from any other on the market because it allows us to clean all kinds of Particulate Filters and Selective Catalytic Reduction units (SCR) used in cars (Euro 6 included), buses, trucks, plant and agricultural equipment.
We don’t cut the filter, bake and weld it. We don’t dip it into a ultrasonic cleaning tank and then oven bake it to dry. United Diesel employs the Flash Cleaning Machine with its Organic Absorbent Emulsifier, flushing the filter both ways and then air drying it.
We are able to monitor back-pressure (mbar) and air flow (m3/h) before, during and after the cleaning process. A printed report then shows a comparison of the initial and final parameters in order to verify the quality of the cleaning.

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DPF Filters, what are they and what do they do?cross graphic

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What is a DPF (Diesel Particulate Filter)?

A DPF is a filter fitted to modern diesel engines designed to remove particular matter or soot from the exhaust gases of diesel engines so that they are not released into the atmosphere. Please see the attached document.

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EGR (Exhaust Gas Recycling valve) how it works - in layman's termscross graphic

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I am sure that if I did a pole of 100 diesel vehicle owners in the street and asked them if they knew what an EGR valve was let alone how it works, I am sure that there would be a higher percentage that does not know. You might find this interesting or even scary but I hope to explain how it works. I have copied a diagram off Google images to help with the explanation.

Clean air is drawn into the air intake through the air filter via the inlet housing of the turbo charger (want to know more about the workings of a turbo see here – link)

As the air has now been warmed by the turbo and the co2 molecules have expanded it is necessary to try and cool the air as the cooler the air the as more reduced co2 molecules result in a better air to fuel ratio. The warm air then passes through the inter cooler which cools the air.

The nice clean air then enters the cylinder via the inlet valves and once the valves close the piston compress the trapped air and then when the injector injects combustion takes place (want to know more see here – link)

The burnt air then passed the exhaust valve and pushes down the exhaust manifold past the turbo, spinning it to help drawn in clean air into the inlet side, then out of the exhaust.

Sounds good because this way the inlet passages to the cylinder are kept clean to allow nice clean air in and the exhaust allows for the burnt gasses to go out.

Problem, because this way the engine runs efficient but also produces more Nox gases, harmful to the ozone layer as it is a greenhouse gas.

So the engine manufactures have thought of a way to reduce the Nox, that is to reduce the oxygen levels in the cylinder when the vehicle does not need to be efficient like at idle and at lower revs.

The birth of the EGR valve. Dirty, used, warm air is redirected into the clean inlet of the cylinder from the exhaust. By doing this less oxygen is drawn into the cylinder thus reducing the combustion temperature resulting in less Nox emissions.

The down side is that the EGR valve and inlet valves get totally carboned up thus resulting in EGR failure and also a reduction of clean air being drawn into the engine resulting in a incorrect air to fuel ratio which cause black smoke, poor running and increased fuel consumption.

Another problem with increased carbon emissions is that it has an effect of the DPF (diesel particulate filter), which is something else that has been developed to help reduce emissions from the exhaust. I will discuss that later.

Below is a picture of a inlet manifold that to be efficient would be totally clean but over a period of time the EGR valve has allowed burnt gasses and carbon to enter the inlet manifold thus restricting the ports. This would cause an imbalance to the air to fuel ratio resulting in poor fuel consumption and more carbon to be drawn back in to the inlet via the EGR valve.

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Injector Leak Back Test, how do I perform one?cross graphic

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Pressure loss within a common rail fuel system can often result in one or more of the following symptoms,

  • Hard or difficult starting
  • Erratic or uneven tick over or idle
  • Lumpy running and hesitation on acceleration
  • Smoke on tick over or acceleration
  • Lack of power or even a total shut down of the system

One of the main reasons for pressure loss is due to excessive fuel being returned to the fuel tank, also known as back leakage. Once the injector/s suffers from excessive back leakage, the fuel pump cannot generate enough pressure to enable the system to operate. This is more pronounced at starting or tick over due to the fact that the pressure generated by the pump is directly related to the engine's revolutions, which are lower at, start and tick over. In a colder climate the engine rotates slightly slower thus lowering pump pressure whilst with warmer fuel the viscosity is thinner thus allowing worn injector parts to leak more, increasing back leakage.

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Injector nozzle tips swell and blow off, why?cross graphic

The first problem with modern day engines is that if the injectors do not seat correctly in the cylinder head combustion gases escape pass the side of the injector. The ECU picks up a problem with the running of the engine and then tries to compensate by sending more fuel to the offending cylinders thus causing a "over fuelling" situation which in-turn causes excessive heat thus weakening the nozzle. This is evident by noticing one of the copper washers disfigured and "melting" up the injector.

Another problem is the possibility of water in the fuel as this is another reason why nozzle tips "blow" off, have a look at this article "Diesel Fuel, Air Vapors And Your Engine Part 1 of 4 By Steve Pollock"

http://www.fassride.com/tinymce/filemanager/files/MovinOutCondensedArticle.pdf

A quote out of article is,

"Probably the most damaging area affected by entrained air/vapors is the engine's fuel injectors. One of the functions of diesel fuel is to lubricate the injectors as they are working. As the entrained air/vapor passes through the
injector it is not providing complete lubricity.
This lack of lubrication for the injector's barrel ad plunger becomes even more critical with the tight tolerances and high fuel pressures used in today's injectors. The entrained air/vapor creates a metal on metal situation. Over time the plunger can start to stick and as it wears, factory tolerances are lost. This causes fuel blow- by in the injector. According to Caterpillar's handbook, entrained air/vapor can create up to 50% greater forces by the plunger on the injector tip. As the fuel comes out the injector tip under high pressure the entrained air/vapor can also act much like an acetylene torch, eroding the injector tip. These two things in combination can lead to the injector tip breaking off."

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Injectors repaired, are they as good as new units?cross graphic

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A repaired unit is an old unit that has been stripped, inspected, cleaned, some internal parts replaced, reassembled and then tested. As some original parts are reused the completed unit will not have the same life span as that of a new unit.

PD Injectors, can you test them?cross graphic

We specialise in all aspects of PD diesel injector testing, repairs and upgrades. As we have the experiance, equipment and passion for PD injectors we can test, repair and upgrade your PD injectors.

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Service Exchange Units?cross graphic

Service exchange units, either new or repaired are units that we send to you and then once fitted you return your old units back to us. If you do not return your old units or they are returned damaged then the surcharge price as indicated on your original invoice and return note will be charged to you.

Service exchange units will be supplied with a 'core return note' an addressed pre-paid return label. (U.K. mainland only) Your old units need to be returned to us, in a repairable condition, within 30 days.

To return 'old units', simply place in the box used to supply the new units with the 'core return note', stick the pre-paid addressed label on the outside and take to a post office. Please obtain a 'proof of postage' receipt when returning old injectors, as the onus will be on you to prove that the old units had been posted should they be lost.

What Condition do Old Units Returned On Exchange Need to be in?cross graphic

If units have been supplied, as service exchange units your original units will need to be returned to us, using our prepaid addressed label, in a repairable condition. This means that:

  • There must be no damage caused by overheating, being chiseled, smashed, bent, distorted, heavily corroded or have parts missing.
  • The old units should not have had acid, water or other aggressive chemicals in them.

Should a unit be damaged, as above, the surcharge price as indicated on your original invoice and return note will be charged to you.

What is an Injector Leak Back Test?cross graphic

Pressure loss within a common rail fuel system can often result in one or more of the following symptoms:

  • Hard or difficult starting
  • Erratic or uneven tick over or idle
  • Lumpy running
  • Hesitation on acceleration
  • Smoke on tick over or acceleration
  • Lack of power or even a total shut down of the system

One of the main reasons for pressure loss is due to excessive fuel being returned to the fuel tank, also known as back leakage.

Once the injectors suffer from excessive back leakage, the fuel pump cannot generate enough pressure to enable the system to operate. This is more pronounced at starting or tick over due to the fact that the pressure generated by the pump is directly related to the engine's revolutions which are lower at start and tick over.

In a colder climate the engine rotates slightly slower thus lower pump pressure whilst with warmer fuel the viscosity is thinner thus allowing worn parts to leak more.

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What percentages of paraffin or heating oil will the DIESEL-SURE test kit detect in diesel?cross graphic

EN 590 DIESEL-SURE TEST KIT Patent pending

It all depends on the specification of the diesel fuel that you are testing but an estimate is as follows: Paraffin 18% to 20%
Heating oil 28% to 30%

We do recommend that the DIESEL-SURE test kit is only used as a guide and should you require a more accurate result that the fuel in question is sent to a fuel laboratory for a full analysis.

 

What will happen if a diesel engine is run on paraffin?cross graphic

EN 590 DIESEL-SURE TEST KIT Patent pending

There are reports of diesel engines that have run for hundreds of kilometres on unadulterated paraffin, however, there are many cases where failures have occurred within a very short period. What is indisputable is that paraffin will ultimately damage a diesel engine.

Firstly, paraffin has a lower viscosity and inferior lubricating properties compared to diesel. Thus, fuel delivery pumps (which must be lubricated by the fuel they pump) will last only a fraction of their normal lives and injectors will wear faster and have an increased chance of blocking. Secondly, paraffin reduces the flame point and cetane number of diesel and causes the engine to run at a higher temperature, often damaging engine components.

 

Why are Injectors Failing?cross graphic

This is a article that I found on the internet written by D. G. Quirk. It is a good insight to the problems that I am experiancing with injectors today. I have tried contacting Dave to get permission to use his article but am unable to contact him.

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