Citroen XM Forum

Well, the change of fuel filter made zero difference to the running.

Starts perfectly, tick over is fine, after about 5 mins at tick over the misfire starts and develops increasingly with sounds of knock.....pumping the bulb sometimes allows it to settle down again.

I still see no air in the flow and return pipes.
Tank cap removed
Tank is most certainly FULL and tank filter sock clean......(god that made a mess !)

Next plan is to hang a gallon tank of fuel and direct feed the pump.

Assuming there are no air leaks...it sounds like the internal pump pressure is dropping, either due to a restriction in the supply pipe, or due to the pressure regulator banjo leaking.

The lift pump over delivers so creates low pressure inside the pump. Without checking the documentation, say about 3 Bar.
The pressurised fuel supplies the high pressure pump and the timing control valve.

At idle approximately 90% of the fuel supply is returned to the tank, but under high load and acceleration requirements more fuel is required by the engine, so less is returned.

The return outlet banjo is a spring loaded, restrictor, which maintains the internal pump pressure.

It might be stuck after sitting unused.
Try giving it a sharp tap to see if it resets.

Temporarily clamping the return pipe should increase pump pressure.

Another alternative is a vane in the lift pump has stuck, so it isn't delivering full volume and pressure, or the shaft seal is allowing air to be drawn in, though normally fuel would leak out.

No need to hang a can, the lift pump will do the work of lifting the fuel.
Ideally use an open receptacle so you can observe the return fuel activity, bubbles, flow...

A strong dose of injector cleaner might be a good idea, in case any pump internals are sticking, or injectors dribbling, which would cause knocking.

Got the LEXIA talking to it



and the Pump timing


Why no pump timing correction ?

I removed the intake manifold to swap off the leak back tubes....I decided to start up to check it running with the new tubes on with no leaks......it started just fine again....ran for a minute or so then started to "chuff" again, always from No1 intake, white smoke "chuffed" out like Thomas the Tank Engine.

Inlet valve No1 on No1 cylinder is partially stuck down...........I have removed the rocker & lifter from that valve, i cannot remove it from the other one on that cylinder....so deffo stuck down.
I conclude = BUGGER

Although there are almost no diesel-powered XMs in Australia, I have been watching this thread with great interest. Very sorry that it's come to this after so much work.

I really don't have any expertise re. sticking valves, but is it possible that penetrating oil (PlusGas?) on the upper valve stem might be able to get into the valve guide? Does the valve reset to the closed position after cooling down? I can see from the photo that there can't be much of the stem above the top of the guide, but logic says there must be some!

Alasdair, not sure if this is relevant, but looking at your photo, looks as if the sensor (needle lift) injector might be in the wrong position.
Private Cars booklet for XM, 2001 050008 Book 2 p.156
specifies Cyl.#3 for the sensor injector, for 2.1TD P8C XUD11BTE.

I was going to say that after watching the videos the engine has a regular misfire and was only firing on three cylinders.

Looks like a bent valve, but it seemed to be firing on all four when you first ran it, so possibly a foreign object has entered via the intake manifold.

Have a look at the valve with a mini camera, remove the cam, try giving the valve stem a tap with a hammer to see if the valve resets.
If the head needs to come off take the manifolds and turbo with it. Undoing the manifold to head fixings is possible in situ, but due to the Egr valve, is a real pain, adding hours to the job.
One specialists is known to cut the turbo oil return pipe, then sleeve it on rebuild. That wouldn't be my preferred option.
General access may be improved as your car doesn't have a clutch cable in the way, but a head gasket job won't be quick. A number of diesel Xm have been scrapped due to the labour cost of a head gasket job.
Book time, on a lift with all the right kit is 17.5hrs. On the floor with hand tools, including skimming (if needed), lapping in valves, etc...30hrs.

Fit new glowplugs while the head is off.

Don't worry about the lack of timing reporting, it was in the first of the two videos.

Thanks chaps.....I am "On" the endoscope idea, I got the one in my "draw of things never used" working last night for this very reason.....

I have battered it with a wooden drift/hammer, no change.

It is strange that it does idle OK at times (even after a period of misfire it has evened out for a period then started to misfire again)....the reason I think we were looking so long for a fuel problem.

I have my COVID jab late morning today, I hope to get the scope into the inlet this afternoon, I will report back as soon as I can (if) get any decent image of the valve........even if I now HATE this engine it is certainly an interesting process investigating what has been going on and what paths have been travelled/are ahead.

I have an whole engine available in the next couple of weeks so with luck I will not need to butcher the rather rare 2.1 Xantia Exclv Estate I have on the drive awaiting some simple pipe work to be finished.

17hrs/30hrs with a ramp (which will not happen) is a ridiculous amount of time for a head swap....I would rather pull/swap engines I think especially as it offers the advantage of access to the subframe/engine bay for cleaning/wax protection and maintenance to the engine bay/engine.

On the 2.5 here we opted for engine out when the HG needed doing, some 10 years ago.
Opportunity for proper and easy access to all the other bits, while out.
Lots renewed for good measure: clutch, belts, w/pump, 'stats, hoses, rads...