Help !! Intermittent tacho and diesel clatter

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Tebster
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Help !! Intermittent tacho and diesel clatter

Post by Tebster »

Help, 1999 xantia 1.9 td
I have a problem that has in the last week suddenly started,first thing in the morning if you turn the ignition on the tacho rockets to the 5k mark then back to its stop, after you have gone through the preheating stage and start the engine the tacho refuses to work and there is a large amount of diesel clatter followed by plumes of white smoke and a significant loss of power.
If you turn the engine off and restart it everything goes back to normal, the car has an ecu which controls fuel delivery etc,could this be at fault or one of its many sensors ??
Any help will be appreciated,
Thank you
Paul
crooser
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Post by crooser »

you could try checking the tdc sensor over the flywheel.
Dave Burns
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Post by Dave Burns »

The ECU doesn't have any control over the amount of fuel injected on your model, that function is still purely mechanical on the 1.9 td, the ECU does however have total control of injection timing.
I doubt wether the tdc sensor is at fault but try this, while the engine is running properly, disconnect the tdc sensor and note the change in engine note, there should only be a very slight change, then reconnet it and unplug the injector lift sensor, a similar change should be heard, note that the tacho should keep reading correctly when either one of the tdc sensor or the injector lift sensor are disconnected.
If by disconnecting either one of these sensors the knock gets very loud, check the tacho, if its stopped then this indicates a failure of the other still connected sensor.
Assuming the above checks do not cause the knock to increase much, disconnect them both, you will now hear the diesel knock become much louder and metalic like as both timing signals are lost and the pump swings to full advance, if this is the same noise you hear when the fault occurs then it more or less rules out both the tdc sensor and the injector lift sensor, since it requires both of them to be off line at the same time to cause this type of timing error.
Go over the wiring and connectors to the timing solenoid valve at the bottom rear of the injection pump, with everyting switched off disconnect the ECU and examine is connection pins for corrosion, do the same for the relays in the ECU enclosure, check the wiring to the glowplug relay and check the glowplugs for any that are dead, strange faults can occure from elsewhere in the wiring where ECU's are concerned.
Dave
Tebster
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Post by Tebster »

Thank you Dave,
Have tested both the tdc & the lift sensor as you advised, both appear to be funtioning correctly,when both plugs are removed from both sensors the clatter is the same as when the fault happens and the tacho ceases to function.
However a few other faults have come to light while doing these tests:
1:Air con relay starts to buzz
2:Cooling fans go into turbo mode
3:Timing solenoid valve clicks rapidly
4:While this is happening the tacho fluctuates rapidly
This seems to happen even if the engine is running or not, but it only occurs in the run position on the ignition switch.
Have checked all underbonnet connections, fuses / relays / ecu etc even had the wheel arch liners out to clean the multiplugs properly.
After checking and cleaning all the above I repeated the exercise inside the car and cleaned all pins on fuses / relays and even swapped relays for known good ones but to no avail.
The bitron unit has also been replaced with a new one, and the relays have been tested on the cooling fans + pins cleaned.
Plugs and connections on the preheat relay have been cleaned with new glow plugs fitted only a month ago.
As you can see I have spent a long time on this problem already, and am at my wits end.
I just dont know where to go from here and any further advise you can give will be appreciated.
Thank you
paul
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AndersDK
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Post by AndersDK »

Hmmm...
Does the '99 (facelift) Xantia has the hidden earth points under the battery - like the pre-facelift models ?
Tebster
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Post by Tebster »

Have checked underneath the battery tray and there is no earth points, only to the right of the battery attached to the inner wing.
Dave Burns
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Post by Dave Burns »

It strikes me you need to be looking for a common cause of all these goings on like a main feed voltage to the ECU fluctuating/missing or an earth point failing.
To eliminate the ECU from the enquiry it will have to be changed for a known good one, so do you know anyone with the same type of car that could help out in this respect, BBA reman will be able to test it for you or even hire you one to try IIRC, if it comes to that, or try and find one in a breakers yard, but later models are a bit like hens teeth in them places.
You could also go and ask the vultures for their opinion and see if they can locate any faults with their clobber.
Dave
P.s by multiplug you mean the big fancy one with the sliding clip, can't remember but is there one one each side.
davey
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Post by davey »

tebster,
had very similar prob on berlingo, see thread 'heater gremlin - public thanks' which had all your symptoms although i had forgotten to mention the tacho throwin a wobbly and very noisy engine - reading this topic brought it all back.
did have another ecu prob on a xantia same as yours but year older this was water in ecu connector and again internal corrosion where connector mates to pcb. as previously suggested its somthing worth checking out.
dave
Tebster
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Post by Tebster »

Yes, there is two of these big multiplugs either side, have cleaned them both and even checked where the main harness comes through the bulkhead on the drivers side underneath the scuttle panel.
I think the next course of action is either to find someone who is willing to let me try their ecu or take it into the makers to see if diagnostics on it find anything.
As mentioned by davey, I will be giving the ecu plugs etc a closer examination and also to locate the supply wires to it and maybe wire some temp supplies to see if this has any effect
Any other suggestions will be appreciated & thank you to everyone so far for some very useful tips.
paul
Tebster
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Post by Tebster »

Update:
Have managed to find out that the problem starts with something that controls the air con relay which is the purple one under the bonnet on the passenger side.
The relay buzzes which in turn sends the cooling fans on to full speed and also causes havoc with the engine management ecu.
Have completely removed the ecu and this relay still buzzes intermittently and sends fans onto full speed, unplugging the bitron, ecu & egr relay has no effect and this relay still buzzes intermittently when ignition switch is in the run position.
Have read that there is an ecu that controls the climate control, and also operates this relay, could this be at fault ?
This ecu is located within the main heater assembly, so is impossible to get to unless you get the dash out.
Or could it be a supply to all of these ecu's that is causing the problem ?
Any more thoughts on this subject will be appreciated.
paul
NiSk
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Post by NiSk »

Have you tried removing the purple mother and seeing if all your problems then go away?
//NiSk
Tebster
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Post by Tebster »

Yes, but nothing seems to have any effect, have gone over the earths yet again but things just keep getting worse, oil pressure light came on this morning together with the stop lights although there is no problem with pressure !
If anyone can figure all this out then they are god in my books...lol
davey
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Post by davey »

tebster,
the buzzing relay may not be a bad thing ... a place to start.
with the relay removed and the ign in the state where the relay would have buzzed measure the positive that drives the relay coil ... suspect it should be about 12v. if it is less, say 7-9v this can cause relay chatter and you have a pwr prob. you will then have to trace further back in the system but at least this would confirm 12v aint gettin from batt to relay with engine off & ign on.
if it is 12v check out the ground side of the relay coil. this can be checked for resistance continuity with respect to batt neg and should be virtually zero.
beware though ... i am assuming the relay is operated by swithing the positive side (some things are ground switched) & it is worth doing resistance chks with batt disconnected.
enjoy.
Dave Burns
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Post by Dave Burns »

What about earths for the instrument cluster.
Ignition switch contacts, these are known to cause things like the climate control ecu to lockup if they start arcing.
Dave
Tebster
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Post by Tebster »

Good point dave, will be testing the ignition switch the weekend, have already tested the relay as davey has mentioned but it looks like the earth side is switched, this is operated from what I can gather by the bitron / climate control and refrigerant temp sensor, does anyone know where I might be able to find this temp sensor on the vehicle ??
As i have already stated this fault happens with nearly all the major electronic devices removed.
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