Xantia 16v getting 12mpg!!! [Fixed]

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

Deanxm
Posts: 3327
Joined: 18 Dec 2008, 17:57
Location: Isle of wight
My Cars: Citroen XM
x 87

Post by Deanxm »

Hi Steven

are there no signs of bad running at all? difficult to start when hot or cold? missing, backfiring?
Have you checked the the fuel pressure regulator is working? the only way economy has dropped from 30mpg to near 10mpg is if its getting too much fuel, a lot too much, coolant sensors being duff or map sensors would cause starting issues hot or cold for the temp sensor at least.
If the fuel pressure regulator has failed or the fuel return blocked you could be getting full pump pressure at the rail and so lots of fuel would be injected over the normal firing duration of the injector but, the O/S would be picking up the fact that too much fuel was getting in (it cant all be being burnt) and when it tries to weaken the mixture i guess to no avail it would throw the engine light on..............

Another reason would be binding brakes, or some sort of resistance in the final drive but again i would have thought you would feel something like that........

D
XM Prestige PRV6 92
Talbot Express Autotrail Chinook 89
Mitsubishi L200 Trojan 14
Xantia Activa 95, sold (missed)

Service Citroen is awesome, it shows me pictures of all the parts i used to be able to buy............
sjj698
Posts: 14
Joined: 02 May 2010, 16:50
Location:
My Cars:

DLC

Post by sjj698 »

Hi,

The connector looks like it should have 10x3 pins, so must be the old version!

The green temperature sensor was replaced with a new one by the garage, i never asked them if it improved anything or if they checked....

I will ask them what kit they use to check it, and see if they have a Lexia.


Thanks



Steven
h2ocooler
Posts: 275
Joined: 01 Aug 2006, 00:35
Location: Chatham, Kent. UK
My Cars:

Post by h2ocooler »

If you can get to Kent I have the adaptor for the old plugs, Im a new Lexia user but would be happy to plug it in and see whats going on.
Rob
2005 Renault Laguna II Sports Tourer Initiale 2.0 Turbo Auto Estate
2003 Citroen C8 2.2Hdi Exclusive Captains Chair
2007 Renault Megane 1.6VVT Cabriolet Coupe Dynamique
02 C5 2.2 Hdi Exclusive Auto Estate (my Dads) DE_FAPPED
sjj698
Posts: 14
Joined: 02 May 2010, 16:50
Location:
My Cars:

Picture

Post by sjj698 »

For others out there,

Xantia 1,8l 16v 1996 diagnostic conector , the old version not ODB




Image
bxman
Posts: 113
Joined: 02 Jan 2008, 22:43
Location: hereford/worcs( malvern)
My Cars:

2 nd vacum pipe

Post by bxman »

the flexible pipe going of into the nearside wing goes a solenoid valve and then on to a charcoal filled canister that is said to absorb petrol vapor from the fuel tank. I believe the ECU periodically opens the valve .

Unlikely to be the problem, but you can bung the pipe close to the throttle body with no ill effect if you think you might have a air leak there,

Have you checked the fuel return pipe for a leak ? there is quite a flow of petrol back to the tank through that.
Try weighting down a good area of newspaper run the car over it.
The leak may not occur on tick over so take the engine speed through a good range. Once you have done so drive away so you have a good light to inspect the paper carefully .
I suspect the car would run like a pig if it was burning fuel at double it's normal rate .
good luck, I hope for your sake you crack the problem soon.
Patrick
addo
Sara Watson's Stalker
Posts: 7098
Joined: 19 Aug 2008, 12:38
Location: NEW South Wales, Australia. I'll show you "Far, far away" ;-)
My Cars: Peugeot 605
Citroën Berlingo
Alfa 147
x 93

Post by addo »

I have the same engine, and recently replaced the fuel pressure regulator as I was suffering stumbling and heavy consumption.

This was only changed after much of what you also swapped (plus fuel pump and filter). Each item was run-tested from a full tank down to near empty. The pressure reg was the only one where a difference was immediately noticeable - I believe underbonnet heat may eventually age them and they lose accuracy.

TPS can be tested off the car. Minimum resistance 1100 Ohms, max 2700. Feed a signal through it (2kHz ideal) and listen for crackling - indicative of track damage - as the shaft is rotated slowly through 90°.
sjj698
Posts: 14
Joined: 02 May 2010, 16:50
Location:
My Cars:

Regulator

Post by sjj698 »

Hi Addo,

I have a scrap yard near me, with the same car in it (ironically with only 60K on it!) so just got the fuel regulator off of that.

As always, no matter what i change there is no obvious improvement in efficiency. I will run if for a few miles and fill it up again, (the only way i can test it)

I also rechecked to see if there was a fuel leak anywhere , but it does not even smell at all.

When i changed the regulator i spilt a bit of fuel and it stinks and is so obvious that i cant suspect a fuel leak.

Once i have done a test of the regulator today, it is off to the garage for an emission test (It is a bank holiday today)


The Haynes manual says check the fuel regulator for obvious damage, but it is all sealed, are there any tests i can do on the old one to see if it is faulty?

Thanks every one, i will keep you posted.

Regards
Steven
sjj698
Posts: 14
Joined: 02 May 2010, 16:50
Location:
My Cars:

thanks

Post by sjj698 »

h2ocooler wrote:If you can get to Kent I have the adaptor for the old plugs, Im a new Lexia user but would be happy to plug it in and see whats going on.
Rob
Thanks Rob, but kent is just too far for me, especially at 12mpg!
addo
Sara Watson's Stalker
Posts: 7098
Joined: 19 Aug 2008, 12:38
Location: NEW South Wales, Australia. I'll show you "Far, far away" ;-)
My Cars: Peugeot 605
Citroën Berlingo
Alfa 147
x 93

Post by addo »

No reliable tests; mine passed some basic standing pressure diagnostics but failed in real life (once warm).

Try to get an actual figure on fuel usage in MPG - I am assuming 12 was just vernacular.

Old school techniques also include checking your manifold vacuum at idle. Look for 18 inches of mercury or slightly better.
Deanxm
Posts: 3327
Joined: 18 Dec 2008, 17:57
Location: Isle of wight
My Cars: Citroen XM
x 87

Post by Deanxm »

really you need to get a pressure guage upstream of the regulator and apply vac to the pipe that goes from the regulator to the inlet, you should see a drop in fuel pressure with vac applied. check the haynes manual for your car or maybe someone here could help with your specific fuel pressure specs.

I have to ask, do you notice it is costing more to run or that you are just calculating a lower MPG?

D
XM Prestige PRV6 92
Talbot Express Autotrail Chinook 89
Mitsubishi L200 Trojan 14
Xantia Activa 95, sold (missed)

Service Citroen is awesome, it shows me pictures of all the parts i used to be able to buy............
sjj698
Posts: 14
Joined: 02 May 2010, 16:50
Location:
My Cars:

Update

Post by sjj698 »

Hello all,

I have taken it for a spin with the new(from an older engine) fuel regulator, and the economy is BETTER

I always measure my fuel economy and get around 30mpg, and up to 33mpg, if i do a lot of town work and it is cold i can get 27mpg. (I once got 22mpg hammering it across Germany, and the thermostat was stuck open, i have since replaced it)

I set the trip and fill the tank,
Here is my last fuel record.
45L @ 31mpg
60L @ 12mpg (town)
55L @ 17mpg (motorway)

(i have done a series of short tests, ~ 30 miles each just to get a rough idea)

The last test was.
1)Fill tank
2) drive 40miles
3) Fill tank , 7L to fill up. ~25mpg (Horray but not great)


It is amazing that the engine can run so well when you just throw fuel at it!


I going to drop it off at the garage tonight, ready for them in the morning!

Also after the 40miles , i hopped out and followed the fuel lines tank to rail to see if there are leaks, and nothing.

Thanks for the tips. I am getting the garage to do an emission test, ECU check (with lexia if they have it) and a manifold vacuum test.
sjj698
Posts: 14
Joined: 02 May 2010, 16:50
Location:
My Cars:

FIXED

Post by sjj698 »

Dear All,

Thank you very much for you time tips and general help.


The car is fixed and is running much better. I wish i could tell you exactly what was up with it, but I poked around with it quite a bit.


1) New temperature sensor (green,bottom) definetly made a difference. (Always reporting 100deg C)
2) The new fuel regulator probably made the most difference.

However i cannot rule out the following.
1)I took the throttle housing off and one of the screws was loose, although i am confident it was not letting in air. The threaded part of the manifold had come loose from the plastic manifold. Glued it back in and tightened up.

2) I took all the connector blocks off, cleaned them with switch cleaner and put back on. (Injectors, temperature sensors, TPS, MAP)

3) I added a 'new' MAP sensor, this did not appear to make any difference. (Connector also cleaned)

4) The garage must have reset the ECU as the ignition warning light turns off instantly now.


The garage were really good and helpful, i can recommend them:
Belbins Garage Romsey nr Southampton , they are a french car specalist. (Price was good as well)
(moderators, please feel free to remove if advertising is not permitted)


Thank you all......


I think i will get a Lexia, any tips?
User avatar
myglaren
Forum Admin Team
Posts: 25366
Joined: 02 Mar 2008, 13:30
Location: Washington
My Cars: Mazda 6
Ooops.
Previously:
2009 Honda Civic :(
C5, C5, Xantia, BX, GS, Visa.
R4, R11TXE, R14, R30TX
x 4888

Re: FIXED

Post by myglaren »

sjj698 wrote:...
The garage were really good and helpful, i can recommend them:
Belbins Garage Romsey nr Southampton , they are a french car specalist. (Price was good as well)
(moderators, please feel free to remove if advertising is not permitted)
No problem at all, in fact, post them in the Recommended Garages & Services forum.
addo
Sara Watson's Stalker
Posts: 7098
Joined: 19 Aug 2008, 12:38
Location: NEW South Wales, Australia. I'll show you "Far, far away" ;-)
My Cars: Peugeot 605
Citroën Berlingo
Alfa 147
x 93

Post by addo »

This fuel pressure reg thing is interesting. Your improvement is at least the fourth I have "logged" on forums when this part has been changed.

Until swapping mine, I was an utter skeptic about it, too.

Yet it remains one of the seldom mentioned failings - people rush towards coil packs, injector cleaning, MAP sensors - frequently to no avail. I have to wonder if there was a bad batch made, with poor metallurgy in the spring.

The only other remote possibility is frequent "running on empty" causing permanent damage to the spring as a pocket of air reaches the reg and is discharged violently into the return line.
citroenxm
Posts: 8061
Joined: 30 Dec 2004, 23:10
Location: Somewhere in North Wales, Anglesey
My Cars: M reg Xm S2 2.1td Auto Exclusive. 269k and rising
L reg XM S1 V6 12v Manual SEi
L 94 XM 2.1 TD auto total resto

2008 Peugeot 207 Sw 1.6 16v hdi. 217k and rising
2010 Peugeot 207 SW 1.6 8v HDi 161k and rising
x 70

Post by citroenxm »

myglaren wrote:Ironically enough, it is Mike that is the closest Lexia owner to you :)

Lexia map
Just like to add, Ive a Lexia too!! NORTH WALES, Anglesey :o

So I guess im alone on that one ! :lol:


Paul
Sharing a pug 207 1.6 hdi Sw 16v.
M reg Xm 2.1 td auto exclusive S2 269k and rising
L reg XM V6 12v SEi auto .. Light project

A very sad...
1994 XM 2.1 d auto
Post Reply