Citroen XM Forum

Good afternoon, quick update for what it's worth. I installed new cap/rotor, spark plugs, fuel filter, charged up the battery, tested cylinder compression (all good) and proceeded to crank the car over. Starter works great, car cranks over at speed as it should. Spark tester indicates I'm getting spark, and I get a green light from the immobilizer (i have the code from the previous owner).

Turns out I am not getting fuel. I dont hear the fuel pump running (I presume it is in-tank). I disconnected what I believe to be the fuel feed line to the injector rail and it is bone dry. No fuel comes out during cranking. I'm now trying to dig up some wiring diagrams or advice on wiring at the pump and the location of the (presumed) fuel pump relay. Poking around at the in-tank connector I'm getting 7 volts but I'm not sure if this is pump feed or gauge etc.

It is progress anyway!
-Mike

The fuel pump relay is mounted on the front of the ECU box. The pump should prime on ignition on.

Here is a link to some scanned wiring diagrams. The v6- Fenix 3 is pretty comprehensive, but the scans are rather low resolution.

http://pepon1.free.fr/CITROEN%20XM_fich ... shemas.htm

Thank you very much for the information and wiring diagrams. It will take me a bit to become familiar with that diagram format, but in the meantime I tried some basic testing at the fuel pump under the rear seat.

Using a separate 12 volt battery I have in the shop, I applied 12 volts directly to the various terminals of the fuel pump. None of the combinations seem to make the fuel pump operate. Am I correct that 12 volts applied to the pump should make it "go"?

Additionally, I dont appear to be getting battery voltage back to the fuel pump wiring. This indicates to me that not only is voltage inadequate/missing to the pump, even if voltage was presented to the pump it would not run.

Lastly, I believe I found the fuel pump relays in front (see photo). The purple relay seems to operate the radiator fan, and the green relay next to the purple relay is always "engaged" when the battery is connected. All 4 relays test out ok on the bench.

Thanks for your help on this. I don't believe we have any Citroen mechanics on the west coast USA so I'm in it on my own!
-Mike

Do be careful with randomly applying 12v to multipin connectors on the car, as serious damage can occur - and a fire risk in/near the fuel tank.

The Pepon circuits above might not go back far enough to cover your car, which is RP5586.
An easy-to-read and colour-coded circuit is included in The Circuit Diagram Project, from Gabor:
viewtopic.php?f=13&t=7592&start=70#p115087
Looks like p.19 could help: V6 12v Fenix 3 ECU etc.

The purple relay is for AC.
The three green relays - edited, see correction below

White Exec wrote: ↑

Mon Nov 04, 2019 7:51 am

Do be careful with randomly applying 12v to multipin connectors on the car, as serious damage can occur - and a fire risk in/near the fuel tank.

The Pepon circuits above might not go back far enough to cover your car, which is RP5586.
An easy-to-read and colour-coded circuit is included in The Circuit Diagram Project, from Gabor:
viewtopic.php?f=13&t=7592&start=70#p115087
Looks like p.19 could help: V6 12v Fenix 3 ECU etc.

The purple relay is for AC.
The three green relays (#813,814,815) work together to control cooling fan speeds (see page 40).
When AC is turned on, one of the green relays should close, and fans run in series at slow speed.
When AC is off, and engine cool, all three green relays should be off.

The green relays are the engine ECU control. The fan relays are mounted behind the left hand headlamp (looking forwards).

The pictures in this attached post indicate which relays do what, be careful to check the wiring colours, as they appear to be in a different order to yours.
The relay with the larger blue feeds is the engine ECU relay.
At this stage you don't need to worry about the o2 sensors, just fuel pump.

I note you have cruise control...

viewtopic.php?f=19&t=8535&start=20#p103777

I'll try to have a look at the wiring diagram for you, but be aware the fuel tank sender contains the pump and low voltage sender components, so don't just apply +12v randomly.

"The green relays are the engine ECU control. The fan relays are mounted behind the left hand headlamp (looking forwards)."
Thanks for putting me right on those, Will. Did half wonder why they were green; fan control relays are black, on the other side.

I've scanned the electrical schematic for the V6-12v using Fenix-3 ECU.

It's pretty simple and the only item of note is that the ECU is locked if the immobiliser isn't functioning and that the fuel pump will prime at ignition on so you should see fuel pressure at that point, but for running the ECU won't trigger the injection relay unless it sees a +12v starter motor trigger signal.

The cable junctions for the fuel pump are; at the ECU, inside the right inner sill, on the fuel tank.
The complete injection loom has further connectors mounted on the engine near the right engine mount and another under the LHM tank, near the gearbox mounting.

If you have a spark, the injection relay is live and passing current and the fuel pump should be running.

Be aware that all wire colours are in French.

Bleu = Blue
Noir = Black
Vert = Green
Violet = Purple/violet
Gris = Grey
Blanc = White
Rouge = Red
Orange = Orange
Rose = Pink
Marron = Brown
Jaune = Yellow.

You are a fine bunch of folks, I can't thank you enough for your help. Let me digest this and will report back, possibly later in the week before I'll get another chance to hit the shop.
-Mike

Any thoughts on applying voltage to the fuel pump (not the wiring coming in, just the pump itself), beyond that it is a bad idea? I have applied voltage (prior to your warnings) to the 4 pins and dont hear the pump run. This indicates to me the pump is shot but does anyone have a diagram for the fuel pump wiring. I can pull the pump and bench test (i.e. verify which of the 4 contacts runs to the pump vs. level indicator), but I dont really want to pull the pump and stink up my house with the smell of gas - I'll hear about it from the wife!


Thank you!!!

If you look at the previously attached, scanned document No.6, you can see the fuel pump is item No.755 and uses Pin3 for the +12v and Pin5 for Gnd.
There is no problem with applying voltage to the pump in the tank, but on the corrrect contacts. The other contacts are for the fuel level sender and low fuel warning lamp.
The risk is that if you bridge the sender resistor with unlimited current +12v, theroretically you could turn it into a heater, or if it cracks due to the heat, could cause a spark.
Having said that, due to the fuel vapour being saturated with hydrocarbons and short of oxygen, it should still be safe.

It would be worth checking the integrity of the Gnd as well as +12v feed.

It would be worth you printing out the attachements in my previous post, they will give you all the information you require to resolve any issues with the engine management system.