And so it goes on! Intermittent power loss and stalling

[Rhothgar]

Chaps,

I cannot find anything regarding intermittent stalling or power loss on S1 Xantii or other similar age diesel Citroens.

I was driving along in my s1 (now 80,000 miles) a couple of weeks ago and it just started to lose power on a dual carriageway. Great place for it to happen. Managed to make it to a farm access road and pull in. Gave a mate a call to bring me some diesel as the gauge had dropped right down. It was on reserve and I frequently run it right down. Long story short but after a few minutes it started and I was able to limp to a petrol station and get some diesel in. Everything has run tickety-boo since then. It revs cleanly. As smooth as ever.

Last night, I was driving along at 60 on an A-road and the power just went. Foot on the floor - NOTHING! Until it died, so I put the hazards on and got ready to phone for assistance. As it was still rolling, I cranked it over and it started and ran fine again. Absolutely 100% tickety-boo.

Fuel is on 1/4 tank so fuel level is fine.

What could possibly be causing this?

My brother suggested faulty fuel solenoid. I thought it was a loose battery connection until he reminded me that diesels will run without a battery once started.

[CitroJim]

Fuel starvation Roger...

My first areas of investigation would be the fuel filter and the in-tank strainer - the latter is well-known for growing an impenetrable coat of fur and crud...

Plenty of reports of it on the forum...

Next up would be air ingress...

[Rhothgar]

Naturally Jim!

But...

If it was air ingress, it wouldn't start easy if there was air in the system and surely it wouldn't be a smooth loss of power and how would it purge itself to magically restart?

I am aware of the in-tank strainer issue but have never experienced it and my thought is at 80,000 miles surely not but it is something I will check.

There appears to be TWO solenoids on the Bosch pump. One above the injector pipes and one on the front which has a little pipe that heads towards the camshaft and then up onto the top.

Naturally, it could be a fault in the wiring to the solenoid(s) which is cutting out intermittently. Like I said, it's happened two in the last 2-3 weeks. Irritating these intermittents issues.

[Hell Razor5543]

There is a microbe that survives in diesel. It actually can do quite well. I have seen photos on this forum where the in-tank strainer is covered in a brown sludge-like substance, and this has got to restrict the flow of diesel. You can get the strainer out, but it is best done when the tank is low on fuel, and remember to tie a string to the wiring (as it can drop out of sight if you are not careful). Access is through the black cover under the rear seat, and care is required, as the 'nut' is made of plastic (somewhere on the forum are the dimensions to make a wooden spanner to fit this 'nut')

[Rhothgar]

This is a good topic!

"XUD Xsara, strange misfire and loss of power"

Forgot to use XUD as a search term before.

[Rhothgar]

Interestingly, I've just measured the voltage at the solenoid which goes to the front of the pump. It has only ONE wire going to it. The other solenoid which I cannot get the rubber cover off just yet as I should have been somewhere which is an hour's drive away right now, that showed 12.86V and 14.23 at the battery. I held the MM on it and can watch it drop. Then turned the ignition off and it measured 10.77V when ignition switched back on.

Maybe it's linked to idle control in some way so as the temperature goes up the voltage comes down?

I can't take a photo at the moment because my phone is full.

[white exec]

Engine ECU putting the fuelling/injection into limp mode (drastically reduced power)?
This can occur if ECU senses high coolant temperature; faulty temp sensor could cause this, even if engine not over hot.

[CitroJim]

The stop solenoid takes little voltage to hold it in... I know this from driving an XUD-engined 405 a good distance with a duff alternator and almost dead battery... Not enough to make the warning lights on the dash glow but the engine kept running...

The microbe growth is not mileage but time-related.. 15 years is plenty!

The other 'solenoid' is the timing adjustment actuator... The stop solenoid is the one with just one wire...

Chris, the XUD9 AS3 pump ECU is not clever enough to have a limp mode!

But, good point, does the Engine Management Light come on during the fault Roger? If it does it's a sure sign of low fuel pressure often caused by a restriction in fuel flow...

[white exec]

Oops - wasn't sure about early Xantia.

[CitroJim]

Oops - wasn't sure about early Xantia.

All it does Chris is adjust the timing according to load - as determined by rpm and the position of the throttle - and coolant temperature and EGR operation...

It lights up the EML if if cannot adjust the timing to the setting it wants and often this is because of low hydraulic (transfer) pressure in the pump resulting from impaired fuel flow...

It does this by calculating the timing by measuring the time difference between the TDC and Needle Lift signals...

It also controls the glowplugs...

[Rhothgar]

Engine ECU putting the fuelling/injection into limp mode (drastically reduced power)?
This can occur if ECU senses high coolant temperature; faulty temp sensor could cause this, even if engine not over hot.

SUX, Brother not HDi

[Rhothgar]

does the Engine Management Light come on during the fault Roger? If it does it's a sure sign of low fuel pressure often caused by a restriction in fuel flow...

No idea, Jim. I am in panic mode when it happens.

I would say that the only two occasions it has happened I happened to be pressing on which I don't normally do.

The solenoid with one wire is the one at the end of the lone metal pipe. It drops to 0V but car still starts when warm. I must take a photo tomorrow when it's daylight again. Could do one now but it might be a bit dark.

[MikeT]

I would also put my money on it being fuel starvation allowing air ingress into the negative pressure lines (from tank to fuel pump).
Normally, there is a clear fuel pipe fitted from the fuel filter to the fuel pump inlet which can be inspected when the engine is running.
If there is a leak in the system up to this clear pipe, air bubbles may be visible as you rev the engine.

[ekjdm14]

Another vote for fuel starvation here, since you say you run on empty frequently (as I read it anyway) I'd change the fuel filter as a starting point, and then look into whether you have a "diesel bug" infestation in the tank. Another thought, is the tank breather free to do its job? If it blocks a vacuum can build in the tank restricting flow.

[Rhothgar]

Another vote for fuel starvation here, since you say you run on empty frequently (as I read it anyway) I'd change the fuel filter as a starting point, and then look into whether you have a "diesel bug" infestation in the tank. Another thought, is the tank breather free to do its job? If it blocks a vacuum can build in the tank restricting flow.

To be fair, I run on near empty once every two months when I've covered 600 odd miles on a tank so not that frequently. I get the gist of what you are all saying though.

I have to state again though that how if it is air ingress could the system purge itself and then restart as if nothing had ever happened.

JIM:

Is this a possibility? I was watching a video on YouTube about testing stop solenoids and it made the point that the positive comes directly from ignition.

Do you think that my ignition contacts are sufficiently burnt out that, from time to time, this may be what is actually causing the issue? Obviously, it is now bypassed but you did comment that they were dead as a dodo and the fix might not work if my memory serves me correctly?