Common Rail Injector Testing

Ok you want your Injectors testing. How can you obtain a fair unbiased report on your Injectors condition. This can be difficult at times as the average workshop will want to make a profit out of the job in hand and it really is not in their interest to pass your injector as good. How many times have I heard of people spending up to £1000 on a set of Injectors only to be dissapointed to find they still have the same problem after spending a small fortune on needless replacement.

You also have with common rail injectors a situation where they are subjected to stringent testing where they must perform within perameters laid down by the manufacturers. The injector is tested and the results are taken at various points:

LOW LOAD approx 300 bar

MID LOAD approx 800 bar

FULL LOAD apprx 1600 bar

The nozzle is opened via the solenoid with pulse width modulation, response time of the solenoid is also measured.

Here is the problem. Your Injector is then mounted on the specialist equipment and the relevant programme is then run. If the fuel delivery drops out of the parameters laid down within the programme by as much as 0.1 mm/3 then it will fail.

On many occasions I have tested Injectors and frequently find they fail test even though the engine is running OK and there are no engine fault codes being generated. I have even tested brand new Injectors and had these fail on test, the truth is the test is far to stringent.

Lets say you have a starting problem, you take your injectors to a local garage or motor factor they in turn send them away for specialist repair. The injectors are tested and the report comes back to you "All the injectors failed test, you need another set we can supply at £195 each!". Now lets be clear about this unless you have had a serious contamination issue it is unlikely all of the injectors are the cause. Yes they may be slightly out of parameter but they are not the cause. A typicle Bosch injector will have a maximum permissable spill return value of around 40mm now lets look at an example of a failed set of injectors.

No 1 = 42mm/3 Fail

No 2 = 61mm/3 Fail

No 3 = 105mm/3 Fail

No. 4 = 43mm/3  Fail

A DIESEL REPAIR CENTRE WOULD SAY ALL FOUR OF THESE INJECTORS NEED REPLACING.

The facts are: 

Now looking at these results its not to difficult to see which is the real problem Injector.

If I had to report on this set of Injectors I would be reporting No. 3 must be replaced this will cure your starting fault, you may also consider replacing Injector No 2 as the return flow is 50% over what is recommended and will eventually soon create a problem. No. 1 and No. 4 are absolutely fine and would not contribute to your starting fault. So you can see understanding these results could save you up to £500 on a set of Injectors. 

Coding of Injectors is another issue that grinds with me, I only see this as another money making exercise by manufacturers hiding behind the Governments climate change mandate.

No I am not a rebel, I too have grand children and it is important climate change is controlled although I do not yield to the fact that all climate change is down to humans or the motor car!. It is important NOX levels are kept to a minimum and we should all do our bit after all we're all just passing through. But too many corporations are now cashing in on this.

Before removing your Injectors it is important to identify the Injector with its relevant cylinder number. Tie a lable to the unit as it comes out of the cylinder, make a note of the serial number and the IMA code, these appear somewhere around the solenoid area. The purpose of this is so if your Injectors are returned with no faults found then you can ensure they go back into their relavant cylinders without the need to spend £100 having them recoded into the ECU. 

Rossy 19.07.2020 10:15

What happens if you have your 6 original Bosch piezo injectors recon and put back into original place with NO new codes? om642 eng in Merc ML.

Dave Neale 09.04.2018 08:50

I cannot code 2 out of 4 IMA codes on a Vauxhall Combo, how can I tell the age of the injectors from the IMA?

ADS 04.04.2017 20:05

1. Did your original Injector have the same amount of digits ?
2. Try coding with Bosch KTS
3. An upgrade of the ECU may be required
4. Faulty Injector

Robert 02.04.2017 01:18

2011 x5 35d usa version coding fails on a replaced Bosch injector. I tried variations of the ambiguous letter and still bmw ista Rheingold will not accept it

kb diesel 25.10.2016 12:15

nice tips injector calibration

Norm 25.07.2016 08:47

Brilliant mate ,no one has a Conscience today . ( Greed is Good ) I whole hardheartedly agree with all you say . I am a Fuel Tech and I know what some shop do