XUD Xsara, strange misfire and loss of power

[johnny625]

I am having a serious issue with the XUD engine in my 228k kilometers, 1998 Citroen Xsara. Basically it starts fine from cold, all glow plugs are fine and they heat up. The car does however has some lumpiness and the throttle is not very responsive. A notable misfire can be heard and the engine does shake a bit too much. Out of the tail pipe there is a slight white grayish smoke that seems to corresponds with the misfire but not a great amount of smoke. I definitely have seen much worse from other diesel engines.

Now as the engine heats up and reaches operating temperature the car does seems to lose power progressively and the acceleration slows to a crawl. At the extreme I am basically struggling to keep up 50 kph despite my foot being planted into the floor in third or second gear. The engine simply won't take revs and if I press the clutch and throw it into neutral the engine does cut out. Restarting is difficult from the starter but somewhat easier if I simply throw it back into gear and lift the clutch slowly while the car is still moving. No noticeable smoke in the mirror. Lucas (XUD 110) injection pump.

Things checked so far:

No significant air in the fuel lines when the engine cuts out. Pumping the primer bulb does nothing to improve the idle.

No issues with the fuel filter and the tank strainer. The engine runs the same when the injection pump is fed from a bottle of diesel.

No wild variations of the alternator supply voltage. I though that maybe such variations can make the fuel solenoid to shut off or get stuck in some midway position restricting fuel flow.

No bubbles of gas in the expansion bottle, no unusual amount of cooling system pressurization, no mayo on the oil cap, the car doesn't lose coolant whatsoever. I don't think its the head gasket.

The injection pump adjusted for the idle speed, anti stall and cold idle as per Haynes Manual long time before the above mentioned issues have appeared.

Any XUD guru's in here?

I can't figure it out

[elma]

You've checked everything I would.
I would now suspect either the diesel pump, timing or the diesel itself.

[CitroJim]

How easy is it to start from cold?

One thing I'd be inclined to check is valve clearances.. There is a suggestion in my mind that you are loosing compression - the smoke colour suggests incomplete combustion.

Valve clearances can close up on an XUD over time but generally the first symptom is hard starting. Hence the question.

[johnny625]

You've checked everything I would.
I would now suspect either the diesel pump, timing or the diesel itself.

That has to be checked also. Unfortunately checking timing is a bit beyond my level of knowledge and amount of tools that I have so I have arranged for a friend of mine who is an an independent mechanic to do the stuff for me. Admittedly he isn't an XUD expert but I think he will manage just fine. I just hope the injection pump doesn't turn bad. Around here no one wants to touch Lucas pumps with a barge pole, they seem to have a reputation for failing and leaking in comparison to the Bosch pumps.

I also have to mention that the car hasn't had any sort of an injector cleaner put into the tank though given the severity of this issue I don't think injector cleaners can do much.

How easy is it to start from cold?

One thing I'd be inclined to check is valve clearances.. There is a suggestion in my mind that you are loosing compression - the smoke colour suggests incomplete combustion.

Valve clearances can close up on an XUD over time but generally the first symptom is hard starting. Hence the question.

Well its not super easy like it starts on the first revolution but it does go within a second or two. Also the car seems down on power a bit even when cold but when it gets hot the amount or power loss is simply astounding. Also the exhaust smoke seems to have a notably sharp diesel smell so I guess incomplete combustion is definitely occurring.

Thanks for your answers chaps. I just hope I will fix my car soon.

[CitroJim]

That it starts OK suggest valve clearances are OK..

Can you confirm this is a Turbo XUD (1.9TD)? If so, then having a Lucas pump, a very likely cause of this may be a perforated turbo boost sense diaphragm on the pump... Looking at the pump, you will see a rubber pipe going to a small circular housing; the other end of the pipe goes to the inlet manifold to sense boost.

A perforation on the diaphragm - which is easy to replace - is likely to give the symptoms you describe...

The Lucas pump is OK and has a very undeserved reputation...

[johnny625]

Yes, its an turbo XUD. I guess it could be the diaphragm on the pump though the rest of the issues must be combustion connected.

[ekjdm14]

This is a bit similar to White's issues (although Bosch pump here) and I'm trying to find a moment to pull the valve cover off and check the clearances.

I have to say though being down on power would point to the diaphragm as Jim suggested, the unburned fuel could be a symptom because when the diaphragm splits I believe diesel is able to travel through the pressure sensing pipe and get into the engine through there. (also makes it easier to confirm a split, if you pop the pipe off at the pump end & it's wet with fuel then you have your prime suspect)

[CitroJim]

I have to say though being down on power would point to the diaphragm as Jim suggested, the unburned fuel could be a symptom because when the diaphragm splits I believe diesel is able to travel through the pressure sensing pipe and get into the engine through there. (also makes it easier to confirm a split, if you pop the pipe off at the pump end & it's wet with fuel then you have your prime suspect)

Precisely right Dan and why it can account for the seemingly large range of symptoms...

[johnny625]

Thank you everyone. The car has been checked by my independent mechanic friend and he doesn't believe that the pump itself is bad. He thinks that the car would smoke far more and it will be far harder to start it if the pump was gone.

This makes the diaphragm pretty much the only option left.

We did however found out that the alternator has poor voltage regulation when the car is hot. The voltage seems to drop from 14.1 to 12.3 volts with the car running especially when many accessories are turned on and the radiator cooling fans turn on. This does make the engine to stutter a bit so I still have some suspicion on the stop solenoid which might be closing partially due to the voltage drop. Also other electronics in the car might be going berserk due to this. Is this even possible? The solenoid itself is not a simple one but it has three wires going into it. I guess this is connected with coded anti start thing.

The voltage rises with increased throttle but still not to the normal (i.e. above 13.5 volts) level.

My friend also thinks that some accessory (the alternator itself, the PAS pump, or the belt tensioner) might be seizing slightly when they get hot thus slowing the engine down and making it stall when at idle. I guess I would have to take the belt out when the engine is hot and turn each accessory pulley by hand and see how easy or hard is to turn them.

Nevertheless I will change the pump diaphragm will be changed ASAP.

[elma]

That could just be a battery lead on the verge of breaking down.

[ekjdm14]

Agreed, have you checked the battery leads & in particular the positive connector. It's commonplace on a lot of PSA cars for the leads to not be the best quality & it could just be this breaking down when hot.

I'd tend to disagree with your friend on the partial seizure of a component causing the engine to stall, as part of the way these engines are governed there is an anti-stall mechanism that would prevent an increasing load from killing the engine

[johnny625]

Thank you for your insights. I also remembered that I can do voltage drop test between the alternator itself and the respective poles on the battery which will show any bad connections. I will also give the battery connections and terminals a clean tomorrow and certainly start looking for the pump diaphragm.

[white exec]

If the main battery connectors are original PSA lead (Pb) lumps, crimped on to the cables, these are known to relax their grip on the cables, and develop internal oxidation and poor contact. Best to replace these old connectors with good quality brass ones, with bolt-down cable clamps. (Clean up all the cable strands back to clean copper.)

With engine running above idling, alternator should be outputting 14.4v or thereabouts.

[johnny625]

Actually the positive connector seems to have been already replaced in the past as it has the a two bolts clamp on it. The negative seems a bit dodgy and not so good looking so I would buy a good quality bolt clamp type of a terminal to replace it.

The alternator never puts out 14.4 v even when no accessories are turned on, on or off idle. The max we measured was 14.1 volts with nothing turned on. Simpy turning on the headlights dropped the voltage to 13.8 v or so which I do believe is a bit of an excessive drop. Just taping the brake knocked the voltage considerably, which also seems bad as I think there are only two 21 watt brake bulbs at the back plus the third stop light that operates when the pedal is pressed.

[moizeau]

Regarding the alternator, if it's similar the the BX the 'brush block' is held on with 2 philips screws and can be changed in situ. Secondly, an ancillary component seizing and stalling the engine is practically impossible. A V ribbed belt will just slip, squeal and then snap well before it affects the engine to the extent you are seeing. Even on a toothed belt it may affect the engine momentarily before it jumps a tooth or several, before snapping. With reference the enrichment membrane. If this is pierced it will only affect engine running over 1500/2000 revs when the turbo 'calls' for more fuel which can't be delivered. Yes fuel can be sucked into the plenum chamber, which if the car is ticking over will go very lumpy/rattly as ungoverned / mistimed fuel is sucked into the engine. If you then put your foot down, you are welcomed by a cloud of black smoke and a car that accelerates like a scolded cat.
All I can offer, having read the above posts is, change the alternator brush block as this is a problem, whether connected or not. Remove the stop solenoid, then remove the rubber boot and spring, then refit. Thus removing a potential problem with not expense. You will need to use the stop lever on the pump (or clutch) to stop the engine.
Does the engine rev freely when cold?
When was the last oil change done? If overdue, change the oil and filter, then get a magnet in the drained oil to see if there is swarf in there.
All the best of luck