Citroen XM Forum

Has anyone got a complete filter unit in good working order, going spare.

So far I've changed the pipes, filter and seals, siliconed up the drain and sensor, fitted a new head unit...and still the damned thing draws air.

As a safeguard has anyone got a Lucas mechanical pump and injectors as well as my car still starts rough and with smoke, but I have had the injectors out and tested and all are apparently perfect..

Does it smoke all the time or just when you start it? could well be air ingress that's causing it, the diaphragms on the primers do fail. To check it you could temporaraly bypass the filter and see if it runs OK like that.

Peter

Hi Will,

I have a nice lovely Lucas Epic if you want...

In all seriousness though, I know of a XM with a mechanical lucas pump that is being broken. Its a 1990 (I think) D.

I'll have a rummage, but I think I have 2 filter units also.

Robert

Peter.

It smokes and misses on cold start, which I'm pretty sure is just down to air ingress, but could be down to the advance solenoid, although when I disconenct it I can hear a difference, so assume that's working OK.

It also tends to blow some black smoke when revved hard, which would normally make me think injectors...

Compressions are fantastic at 410psi cold, after standing a week.

I've already fitted a brand new filter-head with priming pump and still have air.

Robert.
If you have access to guaranteed working stuff, I might be interested.

Hi Dman,it's possible one or more of the delivery valves is not closing fully,not allowing the sharp cutoff of fuel to the injectors.They are fairly easily removed for testing before a pump removal is deemed necessary.If a Lucas fuel filter is fitted i have had problems with both the water sensor and bleed nipple not sealing on these on xud pugs.
robertm

Presumably you have checked the glow plugs. There is a weakness in the fuel line where the rubber pipe joins the metal behind the engine on the drivers side, the rubber pipe cracks where its stretched, not very easy to get at but quite likely the problem if you have changed everything else.

Peter

I've clear piped the flow to and from the filter and the air is definitely at the filter, not before. The drain and sensor ports are plugged and siliconed, but I have wondered about the bleed nipple.

Glow plugs are new and working.

I doubt it's a delivery valve, but after the air leak is sorted, the pump will be next on the agenda to look at.

Sounds as though you have it pretty well covered then. If you have an obstruction in the line from the tank the transfer pump has to suck very hard and draws air in from places you wouldn't think possible, that's the only other thing I can think of, clogged filter in the tank or filler vent blocked.

Peter

Hi Dieselman

Add a bulb pump just before the filter as a temporary item.
Pump this hard without the engine running.
Fuel will bubble out at the point or points where the air is getting in.
I have found leaky filter head diaphram and very small pipe splits this way.
Far easier than trying to pinpoint air entry which gives no visible signs.

John

Is it the labrynth thingy that goes porous?