fuel starvation

Can anyone explain how fuel tanks are meant to breath when the system is of the sealed type. My c3 has running problems that when cold seem to be fuel starvation, only cured for a small time by removing and refiting the filler cap. All fluids require air input to push the fluid along and the above suggest a lack of.

alsie2 wrote:Can anyone explain how fuel tanks are meant to breath when the system is of the sealed type. My c3 has running problems that when cold seem to be fuel starvation, only cured for a small time by removing and refiting the filler cap. All fluids require air input to push the fluid along and the above suggest a lack of.

Is got an EVAP system where the tank is sealed at the filler neck and the evaporating fuel and venting is done by solenoids under computer control through an 'ESS VAPOR ABSORBER'.


Wikipedia touches on OBD2 EVAP systems:

The vapors are adsorbed within the canister, and during certain engine operational modes fresh air is drawn through the canister, pulling the vapor into the engine, where it burns.

The EVAP system should show errors with an OBD2 reader and better (more meaningful) diagnostics can be given by lexia or diagbox.

P0440 to P0457 are EVAP codes, so you can see quite a bit of monitoring going on there. Worth checking for codes if there are no obvious looking problems.

Thanks very helpfull but not encouraging.Modern cars eghhh.

The C3 Haynes manual (available here) has a section on Emission control systems and paragraph that covers the evap system with its charcoal canister and purge valve.

Haynes suggests you can test the the charcoal canister and purge valve by disconnecting the pipes and blowing through them to check the pipes are clear....

The charcoal canister is in the rear wheel arch and the engine purge valve is in the engine bay. I don't see why you can't test that with 12v feed and some sucking and blowing. Then all that is left is a wiring fault or ECU problems.

The purge solenoid valve is arrowed in the picture of the C3 engine bay
There is also a solenoid/ECU electrical connection on (in) the charcoal canister, but I don't have a picture of that. If you strip yours out, we could do with a few photos of the parts

There is also a request for information here petrol-citroen-c3/canister-diagram-t1569.html regarding a diagram for the charcoal canister, which has gone unanswered.

and this topic has a picture of the system parts and requires some answers petrol-citroen-c3/negative-pressure-in- ... t1446.html if anyone can help there too?