Citroen XM Forum

I’ve just changed the o ring on the fuel screw, and I’ve set the adjustments as per the old pump. It starts instantly now when primed, but it’s still lazy to start after standing for just a few minutes. I’m not sure how it has such a bad air leak into the pump. I bled the fuel filter of air also. I guess I need to get some clear hose in place of the fuel hoses so I can see what’s going on.

I’ve also got some problems with the relays behind the headlight as well. I had a seized cooling fan which I’ve now removed and a replacement is on order, but the voltages at various points in the circuit didn’t seem right so I pulled the relay. It was completely corroded, so I pulled the other 3 and they were even worse. Looks like I’m drilling the rivets out the holder and sorting all of that out too.

Sometimes I wonder if I should quit whilst I’m behind!

Further to my last post, I’ve swapped a known good filter head on to my XM. The filter head held a prime for months on my BX whilst standing (I don’t think I’ve started in a year or so), however on the XM I can still hear an air leak after priming the fuel system.

The air leak must be fairly significant as the system loses its prime very quickly.

I can hear air chirping inside the top cover, and feel fuel gurgling through the return hose.

I’ve stripped everything away around the fuel pump, but there are no perceivable leaks - the pump is actually the driest it has ever been since fitting it, as it previously had weeping seals.

I thought that I could hear the chirping more prominently from the boost compensator. Stripping the top off and removing the diaphragm and plunger then blocking the hole made no difference though.

I’ve ordered some clear fuel hose to replace all the engine bay hoses and get a better picture of what’s happening.

I’ve also ordered a non-return valve as a potential temporary fix - it’s frustrating having a car that labours to start so badly.

Are there any common areas for leaks in the under body fuel lines, tank sender etc.? At this rate I am prepared to tear the whole car to pieces just to find the leak.

One final thought that I forgot to add - the stop solenoid being on or off does not make any difference to the air leak. I don’t know if that makes a difference to places that could/could not be leaking.

The diaphragm in the filter head is a common point for air leaks, as is the fuel heater on the side of the cylinder head, but I think yours is out of circuit.

You still have the metal fuel pipe across the top of the intake manifold, the joints there are prone to leaks.

If all else fails try running the pump straight from a can to eliminate the rest of the fuel system.

I've fitted clear lines on the feed side of the fuel pump and I have found that when running there is air coming from the fuel tank.

If I start out with the line between the filter and the pump primed, air slowly migrates from somewhere around the fuel tank, up the feed line and into the fuel filter. The feed to the pump then loses its prime, but keeps just enough fuel flowing for the car to run. When you kill the ignition, you then have a pump and lines full of air, and the car is hard to start.

Are blocked tank pickups common on these? I'll take the hose off the filter at some point this weekend (I'm mostly moving furniture at the bequest of my mrs, but I'l fiind some car time somehow) to see if there's a restriction.

I also had some grief with the cooling fan.

One of the motors was seized, and started causing fuses to blow.



At any rate I've sourced a replacement fan and fitted it.



I've lost the screw that holds the blade on however, which is driving me mad.

During the diagnostics I also noticed a huge voltage drop in the fan switch circuit. This turned into quite a lot of work.









That's the end of those then. I duly went about splicing new terminals in, and fitting them to the old connectors. It was a faff compared to using new connectors, but it meant I could keep the original bracket. I've packed them all out with dialectric grease too, so hopefully they'll last the lifetime of the car with no further attention.









I'm pleased to say that in terms of the electrics, those are all working perfectly now. It was well worth doing, just an absolute nuisiance.

If I can find that left hand thread screw, and sort out the air leak in the fuel system then I'm finally done with this car!

Nice wiring repair there. Grease is the word...I always grease exterior electrical connections to stop corrosion.
I've never quite fathomed using Dielectric grease for low voltage applications (automotive). As far as I know all non-metallised greases are dielectric...not electrically conductive. I use regular bearing grease.
Might save you a few pennies.
I do use silicone grease for O ring installations. Isn't dielectric grease, just silicone grease?

The fuel tank pickups don't normally suffer blockage, but your car has been sitting a long time, so it may have bacterial growth in the fuel.
The base of the pickup has some small mouldings to keep it off the bottom of the tank. It is possible for those moulding to wear down and allow the pickup to rest on the tank inner surface, causing restriction.
The mouldings are approx. 2mm projections.

Thinking about your air ingress issue, I recall having a problem with my sable car.
I traced the leak back to the fuel tank pickup and found there were cuts/bites in the 90 degree plastic elbow of the outlet spigot. I plastic welded it and it appeared fixed for a week, or two, then started leaking air in again.

After much testing of the system under suction, using a transparent hose indicated the issue was the connection between the plastic outlet spigot and the rubber hose.
As the clamp was tightened the nylon spigot was collapsing slightly, so there was only a small clamping force.
I inserted a (10mm?) copper insert to stop the spigot collapsing, which fixed the issue.

It's funny you mention the spigot being cracked, as the night before I had actually found this was a problem on my car by blowing through the fuel lines and finding diesel weeping out. It was pretty badly cracked.



I've sealed it with epoxy, I no longer have air drawn in before the pump or filter.

However, I still have problems starting the car.

If I prime the pump, the primer buton goes soft almost immediately and I can hear air chirping inside the pump. I've replaced all the o rings in the top half of the pump, and sealed the diaphragm in the boost compensator with grease. Still no joy though.

I've also found more damaged wiring, this time below the LHM tank.

Any ideas what this plug is for? The black lead is for the glow plugs, but the blue lead was cut at one end and I cannot find any corresponding wires in the surrounding loom, so not sure if someone has cut out some wiring? There's 12 volts present at the connector, so can't see why the wire would terminate like that other than someone cutting it off.





I'm also getting a bad signal from the speed sensor at times. I see oxidation on one pin, so I'll clean that and see if it improves, if not then I'll get a new sensor.



More annoyingly, the car has developed a rhythmic grinding noise from the nearside front, along with a strong vibration. This happens above 20mph and the car is effectively undrivable now. It feels like a binding caliper or bad CV joint, but I haven't had time to investigate.

I'm probably going to take a break from this car for a bit though, as I've not been enjoying the work for a long time now and all my other cars have suffered at the expense of me focusing on the XM, not to mention my partner and kids. I did a tally up, and I'm at least 400 hours into this car now, so I'm a bit upset that I'm where I am with it now.

The blue wire is probably not used on your version. The body looms tend to have cables for any option.

Poor starting on a diesel with mechanical injection can only be down to:
low compression
timing retarded
no glow plugs (which these do need)
lack of fuel delivery, normally due to air leaking in.

Sometimes one has to take a break from a a project, but I would advise restarting it as soon as possible, otherwise momentum is lost and it never gets done.

I guess this is long overdue an update!

The grinding issue was resolved after taking a breather from the car - one of the steel wheels had somehow seated slightly off centre, so that was an easy fix in the end.

The car has mostly been in constant service since then, with only some minor breakdowns that it has always managed to limp home with.

Recently the fuel pump developed a pretty major leak between the pump housing and the metering head, so I decided to pull the pump out, rebuild it, and do the timing belt, water pump and thermostat too.

















The timing belt, water pump and thermostat have been completed without anything of note, as has the pump rebuild. The pump is back on the car, and whilst it is now definitely fluid-tight, I still have issues with slow starting. I've narrowed this down to either the earth cable or starter circuit, as even with a fresh battery the starter is labouring and the battery terminal gets hot. I've got some spare battery cable here, I'll replace the old one tonight and I will also wire in a relay for the starter - hopefully that resolves that issue.

However, whilst doing this work I have decided to attend to the ABS system, as I've got good access at present due to how much I've removed from the engine bay. This is where I'm meeting with some trouble.

When the ignition is switched on, the ABS light turns on. It does not flicker, so I don't believe it is performing any of the self test functions.

I have tested the relay on my solenoid block (it's the sealed unit Bendix type), and the relay works and the circuit is made/broken as expected.





I have tested all the feeds and earths for both the ECU and the solenoid block. All of these are showing continuity between connectors, and either showing a good earth, or +12v when required.

However, I cannot see that the ECU ever sends a signal to the solenoid block relay coil in order to switch it from earth to +12v through the 30a.

I have opened up the ABS ECU to check if there was anything obviously wrong inside, but the only electrolytic capacitor present is absolutely fine and there isn't really anything else inside testable other than perhaps the transistors.



I'm unsure where to go from here; I don't want to blindly chuck parts at the car, and my gut feel is still that this may not be a problem with the ECU. I'm just unsure where I can go with the testing from here...