Cold engine and problems of injectors. Part 1.

If the performance of any injector is inappropriate in case of a warm engine, it could be easily identifiable, using INPA. For example, using data of cylinder efficiency (../F5/Shift+F6/F3), the amount of correction applied to each cylinder (../F5/Shift+F6/F1), etc.

Moreover, if MSD80 will not be able to smooth out the operation of cylinders (MSD80 detects huge differences in efficiency of cylinders), it will record the error message regarding the inadequacy of performance of current cylinder.

But if any injector is performing inappropriate only when the engine is cold, the problem is much harder to detect.

 

You can check the additional corrections for banks for the cold engine (..F5/Shift+F6/F4, first two lines), but not always they will display the real picture. There are several reasons for that:

a) the max amount of this correction is limited with +/-8%;

b) if the defect is not permanent (not every time), or MSD80 fails to stabilize fuel mixture correction (reach Lambda 1.00), the additional corrections will not be applied.

 

You can check Rough run menu (../F5/F7), but this menu tends to show incorrect data (especially for older software releases). Remembrer: in this menu cylinders are in firing order!

 

If the engine control unit has recorded the error message 3104 regarding uneven running, you can perform test plan of ISTA D, which offers to perform a test for unevenness for cold engine performance (if the problem is detected for the cold engine).

Unfortunately, you can also have some problems, when using this test:

a) it’s not known, what exactly is the math, used during this test, but it’s clear, that during the test cylinders are being switched off one after other. Accordingly – the criteria, which are used to mark any cylinder (it’s injector) as “damaged”, are not very clear;

b) not always this test will give any results.

It is possible, that during this test MSD80 controls misfires, switching off cylinders one by one. But, if the engine defect manifests only as the abnormal ratio of air/fuel without misfires, this test will not identify any defects.

 

One more problem – the defect has to be identified very quickly because in many cases these defects manifest only in first few minutes after starting the engine.

 

Of course, in case of the lean fuel mixture, the pressures for the low-pressure pump and high-pressure pump has to be checked. (../F5/F2/F6). The pressure for low-pressure pump has to be 5 bar (5000 hPa), for high pressure pump: 150 .. 200 bar (150’000 .. 200’000 hPa). Usually, these values correspond to required ones, because, for example, if the high-pressure pump cannot reach the required pressure for a long while, MSD80 identifies this problem. More about fuel delivery problems read here.

 

What to do in a situation, when cold engine vibrates, the fuel mixture is obviously not optimal? In case of critical situation, MSD80 can record an error message regarding trim error for bank fuel mixture. This error message is recorded in the situation if the values for integrators to reach necessary Lambda is above +/-30% for the longest while, and even then it (value -30% or +30%) doesn’t reach required Lambda (typical required value: 0.98 .. 1.00). If the error message regarding trim is recorded, the amount of possible “guilty” injectors drops down to 2 or 3, depending from the engine (2 pcs for N43, 3 pcs for N53). But, if MSD80 manages to reach required Lambda values, even with huge effort – no error message will be recorded.

If the problem (lean or rich mixture) is typical for both banks, it is recommended to check, that the cause of the problem is not the crankcase ventilation. For this reason, you will have to disconnect and close the pipe, which goes from crankcase ventilation valve. Cold membrane becomes harder and can fail to close the valve totally. If the valve is filled with dirt, in temperatures below 0 oC the water inside this dirt can freeze and the valve cannot close.

When the crankcase ventilation is locked, connect INPA and then turn on the engine. In INPA, choose the fuel mixture menu (..F5/F6).

Note: menu description using INPA loader 2.023

 

In the moment, when the heating of wide-band probes start (bar in the first line changes: initially to 99%, then stabilizes to 40 .. 60%), observe Lambda in both banks:

a) bottom bar of the menu;

b) integrators (line No.2 from bottom).

If Lambda for both banks is around 1.00, integrators are in the area of +/-15% and the problem has disappeared – obviously, the cause of the problem has been detected. If the problem is still here – continue searching for causes of the defect.

 

If Lambda for both banks has a stable value around 1.00, observe the integrators. If integrator of any banks is strongly different from 0 (above +/-15%) – this is a sign, that large (additional) correction is required to keep up the fuel mixture. If Lambda for any bank doesn’t reach es 1.00 (the fuel mixture is rich: Lambda below 0.97 or lean: Lambda above 1.03) and integrator reaches (stays by) margin +/-30%: MSD80 fails to reach Stoichiometric fuel mixture even with additional correction of 30% – this bank for sure has problems with amount of injected fuel.

 

How to identify the “guilty” injector?

Open the menu of Systemdiagnosis, sub-menu of cylinder management (../F9/F2).

 

If the problem is is bank No.1 – switch off the cylinders of first bank one by one, if the problem is bank No.2 – switch of the cylinders in second bank one by one.

For example, when pressing F1, the fuel supply for cylinder No.1 is being stopped, menu confirms it.

Note: when the cylinders are being switched off, the engine will run unevenly. To restore normal performance of the engine (after all required cylinders have been checked), press F8.

Attention: in this menu, cylinders are marked in firing order!

After switching off each cylinder return to fuel mixture menu.

As can be seen, MSD80 has turned off the fuel mixture correction for the corresponding bank (integrator is on 0.00: left side, line No.2 from bottom) and according to Lambda value (left side, Line No.1 from bottom), it is possible to evaluate the amount of fuel injected for each cylinder.

When any of cylinders is switched off, the air gets in all cylinders of the corresponding bank, but fuel – only in two or one (depending on the type of engine).

Current example: engine N53, cylinder No.1 switched off. Lambda of the first bank is around 1.4, which means around 40% of air surplus. This value is close to perfect value (quite logical, if we take in account, that with all cylinders switched on the Lambda is 1.00: all injectors are performing correctly, see the first image).

Lambda value has to be memorized, and the switching off has to be performed for all other cylinders of the current bank (in current case: open cylinder management menu ../F9/F2, press F5 – switch off the cylinder No.2, in the next cycle press F3 – switch off the cylinder No.3). Cylinder, who’s injector gives inadequate fuel amount, will show huge or relatively small changes in Lambda.

 

Note: the minimal value of Lambda, which can be measured (and displayed) by wide-band probes of MSD80, is 0.80.

 

There are several possible scenarios.

Examples. Cold engine, wide-band probes heated-up.

 

The 1st cylinder has a problem: leaking injector (incorrect beam) and/or injector doesn’t close properly. Injected fuel amount: increased. Atomization: normal or (usually) poor.
Symptoms:
a) Lambda value of the corresponding bank: lowered (../F5/F6; <0,98)
b) Integrator: significantly negative (../F5/F6; -20..-30%)
c) Offset type adaptations: re-writed to negative value (../F5/F6)
d) Mechanical efficiency of the 1st cylinder: normal or (usually) lowered (../F5/F7, positive values or 1st cylinders bar)
e) Possible: misfires of 2nd and 3rd cylinder of the same bank due to the lean mixture (ELM327; OBD mode 6 data)

Lambda deviation when the 1st cylinder is switched off (relatively to 2nd and 3rd cylinders):

a) huge if injector closes properly

b) small if injector doesn’t close properly

 

The 1st cylinder has a problem: Injector doesn’t close in-time (increased Toff). Injected fuel amount: increased. Atomization: normal.
Symptoms:
a) Lambda value of the corresponding bank: lowered (../F5/F6; <0,98)
b) Integrator: significantly negative (../F5/F6; -20..-30%)
c) Offset type adaptations: re-writed to negative value (../F5/F6)
d) Mechanical efficiency of the 1st cylinder: increased (../F5/F7, negative values or 1st cylinders bar)
e) Possible: misfires of 2nd and 3rd cylinder of the same bank due to the lean mixture (ELM327; OBD mode 6 data)

Lambda deviation when the 1st cylinder is switched off (relatively to 2nd and 3rd cylinders): huge.

 

 

The 1st cylinder has a problem: an incorrect beam of the injector. Injected fuel amount: correct. Atomization: poor.
Symptoms:
a) Lambda value of the corresponding bank: correct (../F5/F6; around 1,00)
b) Integrator: correct (../F5/F6; -15..+15%)
c) Offset type adaptations: not re-writed
d) Mechanical efficiency of the 1st cylinder: lowered (../F5/F7, positive values or 1st cylinders bar)
e) Possible: misfires of 1st cylinder due to the lean mixture near spark plug (ELM327; OBD mode 6 data)

Lambda deviation when the 1st cylinder is switched off (relatively to 2nd and 3rd cylinders): normal.

 

 

The 1st cylinder has a problem: injector doesn’t open properly. Injected fuel amount: lowered. Atomization: normal or poor.
Symptoms:
a) Lambda value of the corresponding bank: high (../F5/F6; >1,02)
b) Integrator: significantly positive (../F5/F6; +20..+30%)
c) Offset type adaptations: re-writed to positive value (../F5/F6)
d) Mechanical efficiency of the 1st cylinder: lowered (../F5/F7, positive values or 1st cylinders bar)
e) Possible: misfires of 1st cylinder due to the lean mixture (ELM327; OBD mode 6 data)

Lambda deviation when the 1st cylinder is switched off (relatively to 2nd and 3rd cylinders): small.

 

 

 

Example: N53B30 U0 engine. Lambda of the first bank is 0.80 (fuel mixture is rich), regardless the integrator -30%; sometimes the error message regarding fuel trim of the first bank is recorded (integrator stays in the position of -30% for a long time, but not even that allows to reach Lambda 1.00). The defect is observed occasionally, only for cold engine and only in first few minutes after turning the engine on.

We don’t know the initial Lambda value (while all cylinders are performing), because MSD80 displays minimal possible value 0.80 (true value is lower than 0.80, but cannot be measured with tools available for MSD80), so we can only evaluate Lambda, when/if any of cylinders is turned off.

Turning off the cylinders, we get following Lambda values:

 

1st off: 0.85

2nd off: 0.87

3rd off: 1.03

Conclusion: injector of cylinder No.3 injects a huge amount of fuel (and, possibly, does not close firmly), which is the cause (or one of the several causes/injectors) why MSD80 is not able to keep Stoichiometric fuel mixture.

Solution: replacement of injector of cylinder No.3. After replacement and coding – delete the fuel mixture adaptations*, create new adaptations and perform the check-up of cold engine performance.

*if OEM NOx sensor installed, please perform Forced desulphation session BEFORE clearing of adaptations (../F8/F2/Shift+F9), as described here.

 

And now: step by step how to act

  1. connect INPA, open fuel mixture menu ../F5/F6, start the engine
  2. check wide-band probes heating PWM (the 1st line), wait till probes are heated (PWM reach 30 .. 60%)

3. at this moment check integrators and Lambda values. If some of the integrators drop down to -20 .. 30%; or Lambda  is lowered (<0,98) – increased fuel amount is identified

4. if 1st bank’s data confirm increased fuel amount, a further test of 1st .. 3rd (1/5/3 in firing order) cylinder is required; if 2nd bank’s data shows increased fuel amount injection, 4th .. 6th (6/2/4 in firing order) cylinders requires further testing

5. quit menu pressing F10 and open Cylinders selective menu: ../F9/F2

6. press F1, if 1st cylinder should be tested, or F6 if 4th cylinder should be tested

7. wait few seconds till cylinder is switched off (you will notice increased shaking of the engine)

8. quit menu pressing F10 twice and enter fuel mixture menu ../F5/F6

9. write down Lambda value of the corresponding bank

10. quit menu pressing F10, enter Cylinders selective menu: ../F9/F2

11. press F5 or F2 (if 1st or 2nd bank is tested), wait few seconds while status bits confirms disabled cylinder

12. quit menu pressing F10 twice, enter fuel mixture menu ../F5/F6

13. write down Lambda value of the corresponding menu

14. quit menu pressing F10, enter Cylinders selective menu for the 3rd time ../F9/F2

15. press F3 or F4 (for 1st and 2nd bank corresponding), wait few seconds for status bits confirmation

16. quit menu pressing F10 twice, enter fuel mixture menu for the 3rd time ../F5/F6

17. write down Lambda value of the corresponding bank

18. quit menu pressing F10, enter Cylinders selective menu ../F9/F2, press F8 to restore normal operation of the engine

 

Compare stored Lambda values. Make conclusions based on examples above.

Note: step by step instruction described for the N53 series engine. For N43 series engine test cylinders 1 and 2 for the 1st bank and 3 and 4 for the 2nd bank.

 

Related entries:

MD80 diagnostics

MSV70/80, MSD80 and Lambda probes. Hidden defects