Xantia HDi Fuel Pump Power Supply

[Steve_M]

Hi all

My first post after searching this forum and trying out all that I had found.

My Xantia HDi 90 BHP suddenly refused to start (full tank). After searching the forum I ran a power feed direct to the fuel pump and it worked. I tested for the brief supply on ignition on and on turnover (voltage) at the pump without luck. I repeated this on fuse 9 (engine bay), again without success (fuse OK). Fuse 7 (engine bay) is live with the ignition on. I bridged the Inertia Switch and saw 12V there. Here on I start to get out of my depth. What else can I try to isolate this problem?

Does anyone have a circuit diagram for my car as the only one I could find was for a petrol model? It would be much appreciated.

Could I run a switched feed from the ignition switch directly to the pump? What issues would this raise?

Many thanks.

Steve

[CitroJim]

Sadly, of all the diagrams I have, I don't have them for the HDi.

That apart, the supply to the pump is fused (F9) in the engine bay fuse box and passes to the pump via the double injection relay, that's the big relay sitting next to the ECU.

One possible fault is a break in the wiring between the engine bay fuse box and the double relay, where the loom runs under the radiator across the front crossmember it's a tad prone to getting damp and wires corroding in it.

The relay pinouts are standard and should be printed on the side of the relay. Trace it back to the supply via the fuse and the pump itself and that will confirm the supply is present or absent.

The relay itself may be duff and these are standard right across all models. Unusual though as they are normally reliable.

The relay is operated via the immobiliser. Is your immobiliser light in the tacho going off as soon as you turn on the ignition?

[Steve_M]

Hi Jim

Thanks for your prompt response.

I have seen the diagram that is printed on the relay and have copied it off. I will have a look at it tomorrow and attempt to trace the wiring back as you suggest.

The only light on the tacho is orange and depicts a key which I guess is what you are referring to. It appears briefly as the ignition is switched on and then goes off.

If I still have problems with diagnosing the circuit problem, would the idea of directly wiring the pump be workable?

Many thanks

Steve

[wheeler]

If I still have problems with diagnosing the circuit problem, would the idea of directly wiring the pump be workable?

The fuel pump relay should only be bypassed for testing purposes, it prevents the fuel pump operating unless the engine is running (apart from the initial priming), if you were to be in an accident & a fuel line was broken the pump would continue to spray fuel everywhere till the ignition was switched off.
Anyway it will be more satisfying to find & repair the problem.

[Steve_M]

Thanks for your help so far and from that I think I've found the problem. I tested fuses and feeds to the relay etc and then from there isolated each wire progressively and passed 12V down them to test for continuity. All was well until I got to Fuse 9 downstream pin and tested the wire from there to the pump connector and found that I did not have a connection.

What I will do now is to take a direct feed to the pump to get it running and see if I can start the car. If that works I am going to use a variation on tricky's fanmod to feed the pump. I have done this already on an earlier Xantia for the fan / rear window heater problem and it worked well. I know that it's not the best thing to do, but I'm reluctant to mess with the fuse box in case I upset something else and I've no idea how to get from the engine bay to the pump with a new wire.

All I have to do now is find tricky's spreadsheet that I think I've got somewhere. I've noticed that the fanmod.xls has disappeared online. If I find it, is there anywhere I can post it and would it be welcome on this forum?

[Steve_M]

I ran a direct feed to the pump and cranked her over and LIFE!

Really pleased to hear the car running again. I just have to apply a workable solution to the problem.

[RichardW]

Steve,

The fan spreadsheet was my handiwork - I've got a copy if you want. If you've got continuity down the wire from the relay to the pump, but no power to the relay, the just run in a new supply from the fuse box to the relay - thus preserving the functionality of the relay.

[Steve_M]

Hi Richard

I found my copy of your spreadsheet, but thanks for your offer to supply a new copy. Thanks also for it in the first place to repair the fan / screen heater problem I had in my previous Xantia.

The fault in my current Xantia is in the final wire through the car to the lift pump, not something that I'm feeling too confident with repairing. Running a new wire from the steering column is far easier and something I'm familiar with, having been there before.

Steve

[Steve_M]

Hi All

Relay fitted (£2.29 Maplins) with a wire (inline fuse) running from the steering column through the central console and under the carpet to the lift pump under the back seat and all's well. The car ran immediately after I completed the job and has been running sweetly since.

Nice cheap job - shame I bought a new pump in anticipation of it being that!

Steve