Xantia HDi Headache.. CURED with some injections...

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citroenxm
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Xantia HDi Headache.. CURED with some injections...

Post by citroenxm »

I thought Id bring this to the main fourm as its got me now.

My Xantia has started again to suffer from Cutting out under high load accellerating.

Firstly 260k. Car has been faultless for some time. but now if I use a heavy foot the engine cuts out DEAD! It wont start till after the key has been off for about 5 seconds or more.

Soo.. heres the headache. Ive just had in a PERFECTLY good running hdi with no issues. So I have swapped the Pump, the fuel rail pressure sensor, the double relay, AND the tank pump and still the car cuts out under load. Over on my blog theres a couple of videos of the live parmeters, The injectors have between -3 and 3 flow correction on them which I consider very good for 260k...

So, what else would you think could be dooing this. Looking at the rail pressure, it fluctuates at idle. Looking at another HDi today with no issues the rail pressure measured was rock steady matching the pressure Ref..

So any other ideas? I have just put a clutch in could I of upset anything gearbox end?

Scratching my head now, as its NOT what I thought it was.
Last edited by citroenxm on 25 Oct 2013, 17:32, edited 1 time in total.
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Mandrake
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Re: Xantia HDi Headache..

Post by Mandrake »

Blocked fuel filter ?
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CitroJim
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Re: Xantia HDi Headache..

Post by CitroJim »

Paul, have you checked the fuel cooler underneath the car? I wonder if it's got bashed and is now a bit squashed and severely restricting the fuel flow?
RichardW
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Re: Xantia HDi Headache..

Post by RichardW »

I think the cooler is on the return side Jim...could be wrong though, I often am!!

That's an oddity for sure Paul! You are right that the rail pressure should be rock steady. Have you managed to get any live data on what happens to the rail pressure when you give it some welly? Presumably it's going high or low, and the ECU is saying 'enough!' and cutting the injection. Where's the pressure regulator - on the rail or the pump? Could be worth a leak off test on the injectors (or as you have a spare set, juet swapping them over) - a cracked injector could be doing odd things to leak off rates and causing the pressure to wobble.

There's not a lot left after that!!
Peter.N.
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Re: Xantia HDi Headache..

Post by Peter.N. »

I would suggest as previous post, have you changed the fuel filter?

Peter
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Chris570
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Re: Xantia HDi Headache..

Post by Chris570 »

How does the ECU know how much it needs to correct the injector flow? (out of interest)

fluctuating pressure at idle to me either means two things it's either reading the pressure incorrectly or there is a problem with the pressure, either generating it or maintaining it. Given that you've changed the high pressure and low pressure pumps and the car will idle my thoughts are that its either the sensor or you're losing pressure.

From what I've read about the HDi ECU if it sees a sudden pressure drop of 1000bar/second it will see that as a fuel leak and cut the engine. It will also do it if the pressure is more than 250 bar below what it believes you should be seeing at that point.

My thoughts are injectors leaking by or the pressure regulation side as you're fluctuating (or reporting as such) at idle.

I may of course be a million miles off but that's where i'd be poking around if it were mine
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Re: Xantia HDi Headache..

Post by RichardW »

^^ that's 2 of us then Chris.... :lol:
citroenxm
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Re: Xantia HDi Headache..

Post by citroenxm »

Thanks for that chris. Ive swapped the pressure sensor from the 90 rail too, the only thing that Ive not swapped across is the injectors from the 90 engine..

Anything over 950 bar of pressure cuts it out.. theres never a massive difference between actual and reference pressure..

Wouldn;t a fuel filter problem NOT allow the car to cruise perfectly smoothly at 80mph when she gets there??? Because she does. infact runs and drivers perfectly well if I use a light foot!

Well ok. IF I feel like it, Ill have to swap injectors over, and put a new filter in too..

Cheers!
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Mandrake
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Re: Xantia HDi Headache..

Post by Mandrake »

If the flow rate is restricted it may work fine with a light foot but the pressure will drop dramatically when the injectors demand greater flow. I don't know about diesels but if you look at the injector on times of a petrol between idle or light cruise and foot to the floor acceleration at higher rpm there's as much as an 8 to 1 difference in injector on time and hence flow rate...
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Re: Xantia HDi Headache..

Post by citroenxm »

So, are we looking at DEFO injectors then?

Heres a couple of Vids from my Blog for evaluation...

http://static.photobucket.com/player.sw ... 165951.mp4" onclick="window.open(this.href);return false;

Another vid...
http://static.photobucket.com/player.sw ... 094740.mp4" onclick="window.open(this.href);return false;
RichardW
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Re: Xantia HDi Headache..

Post by RichardW »

Paul

Something is making the fuel pressure fluctuate at idle. You've changed the the pressure sensor and fuel pumps - and I assume the regulator was swapped with the pump - you are therefore only left with an injector (or injectors). You said in the blog that you thought not injectors as the correction was zero - I always assumed that the correction is the amount the ECU is having to compensate for on each cylinder to balance the engine. No idea how it works it out! I don't think it measures the leak off. Since you've got a set of injectors you might as well do a leak off test, and change any that look suspect - they're not too bad on the 2.0 HDi IIRC?
Peter.N.
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Re: Xantia HDi Headache..

Post by Peter.N. »

If you didn't change the fuel filter regularly on the CX diesel it would actually come to a stop! You got a bit of warning first but you had to change it pretty soon when it started misbehaving. Usually you will only notice the problem when demanding a lot of fuel i.e. when accelerating. My 406 does it if you try to accelerate hard but I think that is running in limp home mode, as is the C5, I don't normally drive fast enough for it to bother me but I will get to have a look at it sometime.

Peter
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Re: Xantia HDi Headache..

Post by citroenxm »

Hi richard

No 8v injectors are a doddle.. yup ive swaped the pump the rail sensor the metal regulator in the fuel line and tank pump and double relay... all from a perfectly fine 90 (both fuel systems are identical so thats NOT an issue)

There is only injectors i guess ive not swapped. If that prooves correct the the pump removed is still fine.

Weather turning now so will do it as and when i can.

Its NOT a filter problem.. after the stop .. and its not a gradual stall or power loss its a STOP dead! Just like that.. it will start up again after the ignition has been off for 5 seconds or more and no less..
Cheers
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Re: Xantia HDi Headache..

Post by KP »

Diff between P measr and P ref, what does this refer to as IMO no pressure related reading should drop to a '-' at any point in any HDi system.

Also on another point the fuel pressure reading seems to slowly climb. It then seems to fire when it gets over 100bar. Is this what its like each time?

Options are really;
Swap the injector wiring over from the HDi90
Compare to another HDi engine and see whats what.

Also the filter could still be an issue! My dad C5 HDi90 would cut out or go into limp mode when it sensed the pressure was to low. Filter swapped and job done! All i can assume is that i had some bad fuel or some dirt got taken into the tank or the filter was super fine and just decided it was going to give me super clean fuel!

The fuel cooler is on the return side but could i suppose cause an issue as it would cause a back pressure to the rail but then that would just keep pressure up and leak off pressure high as well which could cause a fault to be logged but that would more likely occur when your at light throttle at higher revs as the pressure would then build.

Hows fuel economy at the moment according to the computer? Is it about right or is it more economical or more thirsty?
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Re: Xantia HDi Headache..

Post by RichardW »

Will - diff between Meas and Ref is the comparison between what it's measuring on the rail, and what the ECU programme says it should be for the engine speed (and presumably other factors - boost pressure probably!) - so if it's saying -ve figure then rail pressure is below what it should be. The rail pressure should be rock steady at idle. The ECU won't start injection until it sees 120 bar on the rail - as there is no outlet and the diesel is incompressible it should build up very fast - I couldn't see the figs on Paul's vid for start up, but if it builds pressure slowly then that would indicate to me a leak somewhere in the system - eg a cracked injector giving a high leak off flow...