hdi 110 loss of power

[Gibbo2286]

I would suggest a VERY careful inspection of the thin rubber pipes on the electro valves, I've found at times they can have splits that are very difficult to see but are enough to lose the vacuum.

[harryp]

Well, examined all pipes and all seem ok. Disconnect battery to reset ECU. Lexi etc, on Global, no faults. On component diag, it tells me CPH fault, which comes up as communication with siren impossible???????? and will not then communicate with engine ECU - no response..... odd as it was moments ago . No engine faults and no K light yet after a short run and still no power!
It occurs to me with all the chat regarding electro valves etc that I barely know what I'm talking about .!
Which is which? 2 near O/S/F sphere, one behind the other, one under the air inlet pipe, one under the turbo outlet with the butterfly (what is the butterfly for?, as I thought diesels were open feed). For the 2 EV's near the sphere, there is a common feed (vacuum?), one has blue plug (front) and the other (rear) white. Which valve does what? With engine running, should I see a vacuum on the common pipe, or only with it under load? If I can measure vac, will it then transfer to other pipe when engine running (still looking for a suitable tube to connect vac gauge/pump . The sensor on the intercooler is firmly on and the plug in, but cannot follow the pipe - It disappears underneath somewhere - does it go the the turbo for control? Sorry, this is really basic stuff, but I am going round in circles getting nowhere, whilst gently winding myself up and the rain doesn't make it any easier. Seems I am to be consigned to bouncy bouncy DS3 .

[RichardW]

Harry

The sensor on / near the intercooler measures the boost pressure and sends the signal to the ECU. This is the figure you can see on the Lexia (998 mbar from memory?). The pipe is the sensing pipe and will go onto the turbo piping somewhere.

There's a vac pump on the end of the head which supplies common vacuum to the 3 electro valves:
1. turbo wastegate control (bulkhead)
2. EGR valve (bulkhead)
3. Inlet swirl valve (under the turbo pipe, top of the gear box).

2 and 3 are linked in function for EGR valve control and NOX reduction, so you can ignore those.

I can't remember which valve is which at the bulkhead (although I seem to remember the front one is the EGR valve since I had mine disconnected with the vac feed pipe plugged). It is easy however to follow the tubes coming out of them down the back of the engine to see which goes to the turbo and which to the EGR valve.

Control is achieved by the ECU reading the boost pressure and combining it with other inputs (engine speed, throttle position) to work out what signal to send to the turbo electro valve. This in turn varies the amount of vacuum applied to the turbo wastegate, which varies the boost pressure, until the boost pressure comes into line with the required pressure. As Paul says, no vac to the turbo = no boost, so if you bypass the vac side of the EV with direct vac you should get full boost regardless of what the ECU thinks it should be getting. If you drive it gently, this should demonstrate if the turbo and boost sensor is working. If you run with Lexia on, you should be able to see the boost pressure rise. If this doesn't do anything, then you need to check whether or not you are getting boost - either just by disconnecting the hose and checking for flow when engine is revved, or by using a boost gauge if you've got one. If you have, then boost sensor suspect. If you haven't, then turbo suspect (very rare!).

[harryp]

Richard - thankyou. A very fullsome reply indeed .
Whilst I had the turbo pipe off, I did start and rev the engine. Very noisy and no puff, but from all comments, it requires vacuum applying! Weather permitting, I'll see what tomorrow brings .
I supplied some duff gen earlier. Following the re-gas, I drove to Cornwall for Christmas, and it worked fine then. Perhaps it didn't like being ignored afterwards?
Well, Thanks to everyone for help so freely given .
Take care, Regards

[THELABMAN]

Harry,

You're issues sound pretty similar to mines on my C5 HDI from about 2 months back... I'd lost power on mine and when it was booked into the garage for an engine service they found the inter cooler was leaking and replaced it which restored the lost power....

Just before it went in though the engine warning light came on with the service warning and anti pollution warnings with the car then going into limp home mode... the garages work didn't cure this so Richard kindly run his Lexia over it and we found a MAF problem , I replaced the MAF but the car still would go occasionally into limp mode, a further diagnostic session showed up a fault with the MAP sensor on the intercooler which had a broken wire once this was soldered up and shrink wrapped the cars been running great ...

I know it's a bit long winded but your symptoms echo mines almost exactly so I'd check the wiring to the MAP sensor to see if it's ok as I see you mentioned it came up on your diagnostic

Regards

Peter

[harryp]

Thanks Peter, another one for checking today. Certainly appears to be an odd one.
Regards, Harry

[harryp]

Well, have tried swapping ev's, new ev, swap ev pipes, swapped maf; nothing . On revving - car stationary - the turbo pipe sucks in and expands to normal on tickover! So absolutely no turbo; strange, as I would have thought it would put out a bit if is spinning at all. What stops absolutely nothing getting through the turbo and out? Thinking about it, there was a smear of oil on the n/s of the intercooler, but too late really to swap that over now.... but even a massive leak would not stop the turbo blowing, just leaking. Was wondering if the boost sensor on the intercooler might be a goer - if I can remove it in situ? Cannot think of anything else that would cause it to shut down; reading between the lines of the comments .There must be a valve somewhere shutting the turbo down, or it must have a turbo problem. Is it worth a last ditch attempt to change the boost sensor or/and the ev under the inlet hose? Looks similar????? Thanks.....

[citroenxm]

EV under the inlet hose is for the butterfly flap just between the inlet pipe and inlet manifold..

Have you checked for a Vaccuum from the Vaccum pump?? Remember, brakes are not SERVO so they dont need a Vaccum, on a Xantia with lack of Vaccum the only thing you will notice is no turbo!!

Remove the outlet from the Vac pump and start the car, and see if the have vac.. Connect it up and follow the lines to see if its also at the EVs too...

[harryp]

Paul, away at moment having a judder round Norfolk. If swmbo ever sees this I may have to make my own way home!! I do have vacuum, but will put a guage on and see just how much. I still reckon I must have dislodged something replacing the condenser. BTW, is it possible to remove the intercooler without draining the radiator? It looks not due to the bottom hose.???? Trying not to worry too much about it at the moment. Bye for now.

[citroenxm]

You can judge the vacc with your finger... this is interesting. Id love to come down and look over and see whats going on..

urrmmm.. no sadly you do need to remove the radiator to get the intercooler out.. without having the front off..

[Peter.N.]

Have you tried the MAF, that's what caused it on my 406.

Peter

[citroenxm]

I dont think a maf sensor would stop a turbo from spinning... at the end of the day the hdi turbo is STILL a mechanical unit which is driven by exhaust gasses.. they spin the turbine which drives the compressor wheel..theres no vaiable vain on these units which need "waking" up .. so if the turbo is spinning then the boost is being lost either striaght out the waste gate or loose pipe..

im hopefull its nothing exlensive or big. Wouldnt a maf put the cars eml on?

[Peter.N.]

Sorry, didn't realise that was the problem, must have missed something - getting old.

[harryp]

Hi, back again!!
Have checked vacuum with gauge - 25" so seems good. Have connected both EGR's independently to vacuum directly. Taken for run, no boost. Another Lexia session shows a MAF fault - wiring short circuit or open circuit and a similar fault with the air temperature sensor.
So, swapped MAF with the one off the Exclusive. Same MAF fault, but the temp one has disappeared. I guess we now have a wiring fault/faults. Have pulled wires on connector and they all appear tight, and there is no sign of weakness when bending them to check if the wire has snapped/come adrift inside the insulation. Next I guess is to check continuity back to ECU.... Can anyone supply the pinouts at the ECU plug from the MAF plug and also the pressure sensor wiring from the intercooler? The fault appeared not long after I had the aircon re-gassed so have checked wiring loom across engine front just in case it was interfered with during the process, but at first inspection saw nothing obvious. Does the wiring from these two sources go directly back to the ECU before clever stuff happens to pull in the turbo? Apologies that this is turning into quite a saga! Wonder why the MAF etc didn't come up sooner ? All help with the wiring check will be very much appreciated.
Kind regards

[citroenxm]

Hi Harry, nurse the car up to me, and also choose some silver panels and bumpers from this SX HDi that NEEEEDS to go!!

Ill have a look over her for you too!