U codes are an electronic network fault,not particularly related to engine faults.Have you had the injectors tested?.Any excess return spill could cause the fuel pressure to drop sufficiently to cause a cut out situation.Could still be an egr fault,although may not flag a code.Just a thought.

Not too long ago,diesel engines were very simple with very little or no electronics.Modern diesels are a very complicated mix of mechanical and electronic components ,far more than any petrol engine.Running tolerances are highly critical on these diesel engines,and it only needs something to be slightly "off beat" to make the engine run poorly or cut out.Throwing expensive parts at a car hoping for a fix is not the way forward,you can't guess anymore.Your problem of stalling/cutting out is proving very difficult to pin down,and unless the live data from the engine can be read while the fault is occuring, to see what is failing,I think you may have a large task.Although it does appear to be a fuel related issue ,I would not bank on it.I wonder if there could be a problem at the rear of car,related to tank pick module?Does this model have an in tank pump?

Thanks for the advise hardway, I could not work out where diagbox puts the live data, so I have video'd the screen and uploaded to youtube at youtu.be/4___e9EtJWA

You can see the fuel pressure jumping and dropping before it stalls out 2 or 3 times, So I held the revs up and you can see the pressure jumping about.

First chance I will get the fuel regulator removed and check the mesh on it. I hope its that and not the injector pump.

So what do people think it could be.

Thanks for the advise hardway. Today was my first day off work (yep new years day), Drained diesel from filter housing, no debris in jar, Open'd filter houseing and replaced filter and o-ring, checked bottom of filter house , no debris of any sort so bleed the system. Had a look to see where the fuel pressure regulator is. behind air filter box looks really hard to get to. I wonder if is easier to get to it through the passenger side wheel well, (after removing wheel arch liners). Has any one done one of these on a 508 or another hdi engine. The Part is a peugeot/citroen 193339 I believe the delphi part number is 9109-927 same as used on c4, 307,308,407 and funny enough a suzuki jimny.

Thanks for the advise so far.

Hi your reply came through after I was out. Todays adventures with the pug..

had a quick look behind the passenger wheel, while an inspection lap was put in front of the FPR, could I see it, not a chance. So went in through the top, out came the airbox, maf sensor and next bit of the air duct. Unclip then feed and return fuel hoses, undid the electrical connections on the Bracket and removed the 3x13mm Nuts and removed the bracket. Using a mirror with lots of lighting. a lot of swearing I wish I was double jointed at times. I got the FPR out. Remove the o-ring at the nose of it and took the mesh filter off. looking through it with light behind it you could see that more than half of it looked milky/whiteish ?? Bad fuel at some stage ??? cleaned it with contact cleaner till it was spotless and refitted, new o-ring on nose and refitted. Start to Finish almost 3Hrs not a easy job. Bleed fuel system and started engine. still a bit rough at times, So used the PP to tell the ecu that FPR had been replaced, after that silky smooth. Took the car for run, no stalling, fuel pressure at idle should be about 230-250bar it stayed very close to that range no massive ups or down. During the drive I watched the pressure it stayed very close even right upto 1500-1600bar. When slowing down it stayed nice smooth no roughness. I will try it over the next few days and see what happens.

Thanks for the advice.

Ed

Ohhh the tales of woe continue...not as bad. has cut out twice in 3 days. same thing on PP fuel pressure jumps about before dropping below 70 bar the engine cuts out.. but not as quick lots of time to catch it and get the revs up. but still not right. check the injector reading all very close to each other. does not sound like its missing more like running out of fuel type noise and actions. I have ordered up a FPR (from a jimny half the price of the peugeot one.. same delphi part number and same connection) which I will change if for no other reason than peace of mind just incase it has an internal fault. The car is going anyway in March, but my best mate says he would like to buy it (funny enought he was the person using it when it first started all this). If I cant get it cured before march I will use it as the trade in, been given a price of £7500 which seems okay for a 3 1/2 year 56000 mile car. At least changing the FPR swap will be quicker this time....I hope.

Will keep you informed of the progress.

Cheers

Ed

Just a quick update, New Fuel Pressure Reguator arrived on Thur so got fitted on Friday, much quicker this time just under 2hrs. Reset the ECU. So far 300 Miles of stop start driving, stuck in traffic.. basically I have been doing anything I can to get the car to stall. but so far its been perfect. no hunting up and down, no stuttering and pressure is within 3bar at idle.

Will post up once sure fault is fixed. I expect if I do 1000 Miles of all types of driving and still have no problems then fault is fixed.

Thanks
Ed

I was going to suggest the pressure regulator but as I have had no experience with 16 valve engines I kept quiet but I have had all sorts of running problems on the 8 valve due to the pressure reg.

Glad you get it sorted anyway.