C5 2.2HDI LUMPY IDLE

[woodywoodpecker]

Hi Guys,

When i start my car first thing in the morn seems like a misfire for about 2mins then its gone and its ok till the next day. Today i plugged lexia in there are no fault codes i noticed the fuel pressure at idle looked ok 298 bar, But when i rev it to 4000 rpm the most i see the fuel pressure go to is 650-700 bar. I thought it should be up around 1350bar after 3200 rpm ?. Also noticed the 3rd piston on the pump is not switching on and off in live data, there is 11volts at the 3rd piston wiring plug with engine idling. I then removed the 3rd piston from the pump and put 12v feed to it and the plunger moves out ok every time power is applied. Hope someone here can help on what to check next, should i do a leakoff test on the injectors. I do have a spare high pressure pump, fuel reg and rail sensor, Also pulled the fuel pipe off the filter and have a good flow with ignition on any help much appreciated.

[m3vuv]

sounds like an air leak in the fuel system,ie fuel running back to the tank over night.

[oldford]

Doesn't the Lexia tell you how much the fuel pressure is expected to be? Most diesel ecu's will show that figure.

[woodywoodpecker]

sounds like an air leak in the fuel system,ie fuel running back to the tank over night.

m3vuv, The car starts first turn of the key and runs perfect for about a min then the lumpy idle starts then after about 2 to 5 mins it runs smooth again. Would it not start properly if air was present at first start up.

[woodywoodpecker]

Doesn't the Lexia tell you how much the fuel pressure is expected to be? Most diesel ecu's will show that figure.

oldford, Thanks for your reply i have not seen in lexia where the expected fuel presure should be, i have only seen the turbo presure what is expected. Could this be the fuel regulator or rail sensor playing up or injector leak off, iam not sure what to do next.

[Larue]

As you have spare high pressure pump then start from fuel rail pressure regulator changing. Just monitor fuel rail pressure and rail pressure regulator duty cycle. It should stay even. If it's jumping all over the place replace regulator.
You haven't mentioned what engine management system it is, but on some of them( EDC15) on the end of rail pressure regulator there is metallic filter. It's worth to check that under magnifying glass. Could be partially blocked.
If you are in doubt about injectors leakbacks - just check them!

[woodywoodpecker]

As you have spare high pressure pump then start from fuel rail pressure regulator changing. Just monitor fuel rail pressure and rail pressure regulator duty cycle. It should stay even. If it's jumping all over the place replace regulator.
You haven't mentioned what engine management system it is, but on some of them( EDC15) on the end of rail pressure regulator there is metallic filter. It's worth to check that under magnifying glass. Could be partially blocked.
If you are in doubt about injectors leakbacks - just check them!

Larue, Thanks i will check that tomorr what i did notice when i started the car this morning was that once the uneven idle started i turned the car off, Restarted and again the car idles smooth for a min then starts lumpy idle again. I can turn off and repeat this with the same result untill approx 5mins then its smooth all the time. The ecu is a EDC15C2