Problem with fuel pump, Xantia won't start.

[xantia_v6]

Did you check the inertia switch (1203)?

[wheeler]

Did you check the inertia switch (1203)?

I believe the OP has already tried bypassing the inertia switch.

If the ECU is not giving the earth signal then you must confirm that the ECU itself has good earths at pins 36 & 54, Disconnect the ECU then you must check them under load with a bulb (not an LED). A resistance or continuity check is not really any good.
Remove the earth bolts at MM01 & MM02 & clean all the terminals & the mating faces.
I'd be amazed if this wasn't caused by something during the gearbox removal.

[CitroJim]

I'd be amazed if this wasn't caused by something during the gearbox removal.

Yes, fully concur and likely to be an earth wire that's not been reconnected or has been damaged in the process of doing the clutch ...

[moizeau]

Is there a speed sensor on the top of the box? Not sure whether it being disconnected or damaged wiring would stop it starting though.

[CitroJim]

Is there a speed sensor on the top of the box? Not sure whether it being disconnected or damaged wiring would stop it starting though.

I did wonder the same about the TDC Sensor Pete but then again if it was faulty the ECU would not know until it had seen a failed start attempt and for that it would have had to fully energise the double relay to get the injectors ready and the pump whirring in readiness for a start attempt...

When the ignition is first turned on the pump will run for a few seconds to pressurise the fuel rail but then stop. It'll only then restart on a successful engine start...

But, being Citroen, you never know very much worth checking...

[wheeler]

Yes, I would still expect to see the fuel pump initially priming if there was a crank sensor fault.

[DS-Reval]

Hello, was this problem ever solved ? I am asking because I have a similar problem with my Xantia, but it is a phase II (break) from 2000 with a 2.0 petrol engine (without turbo). Is the electrical scheme the same as shown here ? The fuel pump has been tested by connecting the two wires at the relay under the bonnet. Then it works, so the pump and wires from relay to pump must be ok. I purchased a new relay and replaced the old one, to my surprise, it didn't solve the problem, the fuel pump is still not starting at all. I have not replaced the clutch or any similar work, the car has been standing still for some years and during the standstill, where I at irregular intervals started the engine, it suddenly just didn't work.

[xantia_v6]

I beleive that these are the injection diagrams for your car:

[xantia_v6]

Does the engine start if you force the pump to run by bridging the relay?

[DS-Reval]

Thanks, I will have a look at it. I have not tried to start it with the relay bridged actually, since I had to disconnect the relay altogether to bridge the connection and so I didn't dare to try a start, but I might find a way to bridge the relay while it is in place.

[DS-Reval]

Together with my son we measured today the voltage on point 2 of the double relay, when turning the ignition key to the point, where the fuel pump should start. Only around 10V, although the battery has around 12.4 V and enough to turn the engine around with the starter without too much difficulty. I wonder if 10V would be insufficient to trigger the relay ? I have not yet found a way to bridge the relay when installed, but I see that the same part of the relay is also connected to part 1135, what is that part - the ignition coil ? So it seems that not only 11 and 9 should be bridged, but also 11 and 1.

[xantia_v6]

10V should be enough to operate the relay, but is suspiciously low. You should investigate where the voltage is being dropped. It may be a broken or corroded wire, or a corroded connector pin.

[DS-Reval]

The measurement with 10 V was with a random and not very good mass/earth connection. When connected directly to the negative on the battery it was almost 12 V (11 point something) on pin 2 at the relay connecter. However when we measured the voltage between pin 2 & 10 with the ignition key in the position where the fuel pump should operate it was only around 4 V, most probably too low to operate the relay. So somehow the connection back to minus via pin 10 at the relay (through the ECU) must be quite bad. This measurement was done with the relay disconnected, I wonder if this influences the connection from pin 10 through the ECU to minus ? I think theoretically it could. We made the connection better at point MM02 and tested the connection from pin 2 at the ECU connection with an ohmmeter, it showed a low resistance, but then later I read here above that a test with a bulb is preferable. Also I overlooked that there is also a connection from the ECU to MM01 that we have not tested so far. So that is one of the next steps.
However I read in some other posts with similar problems that there is a separate "CPH" that it seems could also be the culprit, even if the immobilizer error lamp doesn't light up. Since the car has been standing for very long periods without a connected battery there could maybe an issue with non-recognition of the codes in the key ?

[xantia_v6]

It is my understanding that the immobiliser (and CPH) do not stop the fuel pump from running, that is entirely controlled by the ECU.

[DS-Reval]

MM01 seems good also, but what is wire 822 (A&B) supposed to do ? It seems to be able to influence operation of the relay also. Pin 3 of the relay and pin 34 on the ECU should be connected, the connection is not very stable on my car though. And what is 82-- on the scheme 12.6 ? That is supposedly where 822 A and 822 B should meet ?