Renault T Fuel system Fault

Carl Technician Ireland Posted   Latest   Edited  
Heavy Duty
P228F — Fuel Pressure Regulator "A" Exceeded Learning Limits - Too High

Hello everyone, hopefully this case study is helpful to others as i'm certainly in debt to others on here for their fantastic informative posts. I work on HD trucks and rarely write any case studies but this was one that I found interesting and really showed the power of the Pico.

The truck in question was a Renault T, DTI11 Euro 6 engine. This engine is the same as used in certain Euro 6 Volvo trucks also. It is an inline 6 configuration engine, common rail.

This truck came in with a P228f00 code, Fuel regulator at maximum learned parameters. It was not active at the time but stored in memory and the truck sounded smooth with no signs of misfire etc. Freeze frame data showed it occurred reasonably frequently, about 2-3 times per day with the driver reporting a limp mode condition when it happened.

Looking for TSB's I found one in relation to this code. It explained that this code is set after 15 seconds of continuous running where the fuel regulator is at maximum (it did not specify which regulator). It explains that fuel pressure is still within spec so does not set a 'fuel pressure too low' code. This injection system has 3 regulators.

After a little bit of research I confirmed the operation of the system. While being a common rail system this system utilises 3 standard solenoid injectors and 3 pumping injectors. The pumping element of the injectors purpose is to supply the rail with pressure, these are camshaft activated and look much like the Delphi E3 injectors yet internally do not operate the same. The pumping injectors also have a solenoid injector combined with them so essentially we have 6 solenoid injectors with three pumps attached to three of them. Each of the pumping injectors have a regulator and there are two pumping phases for each injector per camshaft revolution, so 6 in total.

diag​.​net/file/f45oyl9fh… diag​.​net/file/f3myaero7… The TSB suggested numerous possible causes including Rail pressure sensor, air in fuel system, rotated cam lobes, electrical connection fault, PRV leaks and injector faults. Unfortunately not having a dealer level scan tool, many tests in the TSB were not possible to accomplish, particulary the high pressure system check whereby we can individually actuate each pumping injector pumping element and check for pumping efficiency.

I checked and confirmed low side fuel system condition, all was in order. High side pressure commanded vs. actual was matching on live data. No codes were active.

Checking the camshaft showed no visible signs of rotation although this was always in the back of my mind as I have seen them move before very slightly and become difficult to diagnose. I also checked pumping injector preload at this stage and found all in spec.

My next step was to check fuel rail pressure with Picoscope, all looked in order until I zoomed in and started to analyse the waveform details.

As we can see the waveform is not uniform and points towards our issue. diag​.​net/file/f4qnu89dr…

As you can see in this labelled picture the problem is quite evident. We have a pumping loss in one injector, I have labelled them 1,2 and 3 but these injectors are actually on cylinders 2,4 and 6. While I didn't save the capture by capturing metering solenoid current I was able to confirm that it was in fact cylinder no.2 pumping injector that had the loss. This injector was not able to keep up pressure under load and was setting the code. diag​.​net/file/f5ve69b02…

As per the customers request we replaced all 3 pumping injectors and the results are below. A nice even pressure across the board with no losses of pressure. diag​.​net/file/f23768ope… Hopefully you enjoyed reading this and it helps somebody in the future.







Rick Business Development Manager
Rick Default

Good job on your diagnosis and writeup. The pictures file sizes are so small they are not legible when increasing their size to view them.

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Rudy Technician
Rudy Default

Rick- They look ok to me. Same as any other pictures DN folk put up. Are you clicking on the pictures?

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Rick Business Development Manager
Rick Default

Rudy, Was opening the pictures into another tab on the browser. Clicking on the pictures provides one with a good quality. Thanks, Rick

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Christopher Technician
Christopher Default

Excellent write up, nice to see the detail in the report. Some very helpful information. We have the Volvo version of this engine in NA with all the same fuel system principles. Great job

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