Citroën C8 2.0 16V won't start; Fuel Pump

[christufus]

Hi everybody,

I’m having a problem with my 2007 Citroën C8 2.0 16V 140 PS. It won’t start The engine turns over, but when I turn the ignition on, I can’t hear the fuel pump. The fuse is fine and I’m measuring 12.54 V at the input and output (both with and without the ignition on, which I find a bit odd; Question 1: is there a constant voltage here and does the relay only then release the operating current to the pump?). Unfortunately, there is no voltage at the connector at the bottom of the fuel tank.
I haven’t been able to locate the relay yet, but I can hear a clicking sound when the ignition is switched on. Question 2: Where can I find the relevant relay?
I have since bypassed the fuel pump using another battery, and it runs. However, with the pump bypassed, the car still won’t start. Question 3: Does this suggest a bigger problem than just the relay or power supply?
I somehow suspect it might be related to the immobiliser or something similar, but I’d like to rule out the relay first.
Question 4: Could it be related to the fact that the car always has power-saving mode activated, even when the battery is being charged in parallel and is fully charged? Only disconnecting the battery helps to exit this mode.



Now for a strange fact:
When the problem occurred, I fiddled around a bit and tried a different battery (without success); when I then reconnected the original battery (fully charged), it started up. After switching it off, I wanted to read out the error codes (as the engine warning light was on), but then it went back into energy-saving mode and hasn’t started since. Even when I tried the same thing again.
The fault memory showed several faults relating to the engine: lambda sensor and ignition coil, and relating to the system: fuel control circuit.
The ignition coil was replaced not too long ago.


I know this is a lot of information, but I hope someone has an idea, or even a solution, as the problem maybe is a known one. Unfortunately, I haven’t found anything about it.

Thanks in advance to all the helpful mechanics

Best regards
Christoph

[mickthemaverick]

The fact that the car insists on being in eco mode combined with you only reading 12.54V suggests you possibly have a weak battery. AS a 'somewhere to start' I'd suggest you disconnect the battery and place it on overnight charge. Then reconnect it using the procedure in the link below and then see what you have. If it still doesn't want to start then a diagnostic test is the way to go.

viewtopic.php?p=601679#p601679

[PaulC5]

Most cars if you leave the key in the ignition and open the driver's door a warning is given. If your car does this it suggests the key is being recognised by the immobiliser.

When turning it over, is the rpm being shown, if not the crank shaft sensor might be faulty.

[christufus]

Thanks for your replies.

I’ve already charged the battery, but I’ll go through the BSI pairing process again, as the instructions I had described it slightly differently.

The key is recognised and the rev counter is showing the correct reading.