REV COUNTER ERRATIC

[DublinChris]

I have done a search but not found anything specific so here goes. 1998 Xantia Series 2
I had a coolant leak - hose from the Y junction running back down side of expansion tank cracked and sprayed coolant all over diesel pump area and down block. It cracked just at back of jubilee clip holding it to Y connector. I made a repair and had engine running for a while in driveway to get it up to temperature and check for leaks - all seemed good.
Short time later put key in ignition and rev counter was flicking around before starting car - also clicking noise like a solenoid sticking. Anyway started car and all other electrical issues seemed to be working ok and rev counter settled down. Tried a few more times putting key in and sometimes ok and sometimes flickering. Is the problem down to maybe a connection getting wet from coolant? or some other explanation?

Thanks Chris

[evilally]

I have a similar problem. When I start the engine, the rev counter will often flick all the way round the dial and then back to zero. It will stay at zero while the engine runs (with very advanced timing). Stopping the engine and restarting usually returns normal operation. I'll be looking into this tonight hopefully (I'm going to try another crank sensor). Interesting what you say about the coolant leak. I lost about half a litre of coolant when I removed that same hose to get access to glow plugs. I can't remember now if the problem started before or after this.

[Jaf]

I had a problem with the rev counter sometimes, when starting the engine the rev counter wouldn't work at all and the engine sounded awful. With mine it was when the alternator got wet with LHM from the pump. Once I fixed the leak the problem stopped.

[CitroJim]

Chris, what engine?

I'm assuming from the description of the bit of the cooling system that split it's a 1.9TD..

In which case, if it is, have the lid off the ECU box and check the pump ECU connector. I've seen water get into them and corrode the pins. It can run down the wires and werak havoc..

The ECU drives the tacho...

The ticking could be the aircon authorisation relay next to the ECU. That one is driven by the ECU too...

[DublinChris]

Chris, what engine? I'm assuming from the description of the bit of the cooling system that split it's a 1.9TD..
In which case, if it is, have the lid off the ECU box and check the pump ECU connector. I've seen water get into them and corrode the pins. It can run down the wires and werak havoc..
The ECU drives the tacho...The ticking could be the aircon authorisation relay next to the ECU. That one is driven by the ECU too...

Hi it is a 1990ccTD series 2.

My mechanic disconnected the rev counter from under the airbox and the needle was still flickering. Also ticking at diesel pump and also sound of glow plug turning on/off. This all with key in ignition at start position but engine not running. He checked for loose wires all seemed good. he connected up the diagnostic computer and all good there no faults showing up except the aircon as you say but I dont have aircon. He also disconnected the ecu and opened it up as he thought from some white deposit around pins that there might have been an overheating problem but everything looked good at back of pins in box. The thing was that the computer was showing an engine speed when rev counter was flickering even though engine was not running - you could see the revs going up and down through 1400- 3500- 5500 rpm and so on - on the display. This morning when I came out to start car from cold all was good - an hour later when engine hot the flickering started and has done so on and off during day. There are no other issues car is driving fine and once you start car the rev counter settles down and behaves normally. It is only the point when you turn key to start position and wait for glow plug light to go out that it is flickering around to 6000 and back!

[CitroJim]

In that case Chris it may well be just the old problem of bad contacts in the instrument pod...

The connection to the gauges proper to the printed circuit behind is via small 'fingers' and these often go intermittent and cause wavering gauges...

Is it just the tacho or are other gauges doing funny things?

[DublinChris]

In that case Chris it may well be just the old problem of bad contacts in the instrument pod...The connection to the gauges proper to the printed circuit behind is via small 'fingers' and these often go intermittent and cause wavering gauges...Is it just the tacho or are other gauges doing funny things?

It is exclusively the rev counter absolutely everything is working fine. I did have a problem once before when a white wire corroded down below the water bottle. This caused electric windows to malfunction/clock to go off rev counter to jump and I think central locking to malfunction there may have been other small things but cant remember - anyway wire was repaired - the copper had turned green and went to dust. That was only time before when rev counter jumped.

Is there a fix for the bad contacts in instrument pod?

CHRIS

[CitroJim]

Is there a fix for the bad contacts in instrument pod?

Yes, it's a bit tricky as it involves dismantling the instrument pod and carefully cleaning the contact fingers and their respective contact pads on the circuit board...

[DublinChris]

Many thanks for your help. I will have a chat with my mechanic and see what we can do. Its funny sometimes how these things show up with some other problem which then tends to muddy the water. The fact that I sprung a leak last Saturday and coolant sprayed/dripped over most things on right side of engine/compartment like diesel pump/wiring loom above pump, alternator belts etc etc you sort of think that maybe the coolant wet some contact or other causing the rev counter to go mad when up to that point everything was good. I have just 190,000 miles up and car is in use every day. I have just had diesel pump reconditioned together with timing belt/water pump replaced and the steering pump re- sealed. Car was going so well after that and then the old brass 3 way connector split releasing coolant. I replaced that and then a week later last Saturday the hose cracked as I explained before followed by the rev counter. Have disconnected the immobilizer as well during diesel pump rebuild as the wisdom seemed to be that potentially it could give trouble in the future so deal with it now.

thanks again for your input.

Chris

[DublinChris]

Is there a fix for the bad contacts in instrument pod?

Yes, it's a bit tricky as it involves dismantling the instrument pod and carefully cleaning the contact fingers and their respective contact pads on the circuit board...

Well another issue raised its head today - the engine management light is going on and off!

I went along to my mechanic and he plugged in diagnostic tool. It showed up that the diesel pump was advancing assuming that engine was running at a different speed than it actually was and wanting to advance pump. Also at idle while doing the check there was harshness in engine note.

He also disconnected the three connectors to diesel pump but rev counter needle still fluctuating with engine off but ignition to start position and as in earlier post the diagnostic tool was showing the different rev readings even though engine not running. The ecu is believing the engine is running even though its not! This seems to be why it then wants to advance pump.

It also seems to be at low revs or coming to a stop at traffic lights for example that the light comes on but once you rev engine the light goes out. I have just done a 15 mile run on Mway @ 2500/3000rpm approx - between 60 -70 mph and arrived home and management light did not come on once and rev counter worked fine all along the drive.

My mechanic is suggesting removing the rev counter connector below air box which has 3 wires leading back to the ecu and then one by one checking them to see if there is a crack/break - or maybe coolant did seep in somewhere. He seems happy that there is nothing wrong with the diesel pump or connections to it. We also checked where the original solenoid for imobiliser is taped into position - the imobiliser is disabled but solenoid still connected. He feels that problem is within the engine compartment - while not ruling out a problem in instrument pod.

Its proving a real brain tester trying to get to the problem of why initially the tacho went wild and now the other "associated" issues. One feels that if tacho problem can be resolved it will sort the ecu issue. The ecu issue was not showing up on Monday when we did first diagnostic check but the engine running when not was.

Any help to get to the bottom of problem would be appreciated

[evilally]

I would check the connector to the needle lift sensor. This is the injector with the wire coming from it, the plug for it is right next to where you had the coolant leak. If you unplug this sensor, the pump will default to full advance, and the engine management light will come on. I wonder if this is the problem in the first place, as I believe the ECU can use this information to feed the rev counter (in addition to the crank sensor). If it was giving spurious readings, would it cause an issue with the rev counter? What diagnostic tool is the mechanic using? I wonder if a Lexia would reveal more?

[DublinChris]

I would check the connector to the needle lift sensor. This is the injector with the wire coming from it, the plug for it is right next to where you had the coolant leak. If you unplug this sensor, the pump will default to full advance, and the engine management light will come on. I wonder if this is the problem in the first place, as I believe the ECU can use this information to feed the rev counter (in addition to the crank sensor). If it was giving spurious readings, would it cause an issue with the rev counter? What diagnostic tool is the mechanic using? I wonder if a Lexia would reveal more?

I believe this is the equipment used

http://img242.imageshack.us/img242/1248/eliteix8.jpg

Thank you for this. The diagnostic tool is a Citroen item that plugs in where fuse box is under dash. My mechanic is a Citroen trained mech although the garage is now multi dealer - used to be a Citroen dealer and I bought my Xantia from them in 1998. They have always worked on it for me.

If there is an issue with injector as you describe in that maybe there is a fault with the connector - from coolant leak - would I initially have been able to drive the car with just the erratic rev counter needle? It seems to be good from cold first thing in morning and then as day progresses the erratic needle issue becomes more of an issue. It is just at the start up phase/ glow plug once car starts even when warm that it becomes erratic and then give it a few revs the needle settles and is perfect whilst driving. The ecu light and advance issue just started today.

As I said before with the diagnostic tool plugged in and just ignition switched to on but car not started the engine speed was showing on the diagnostics with rev counter fluctuating. The reading was suggesting that the engine was running when in fact it was not.

I cant help but feel that the coolant leak has something to do with the problem. The leak was up high above diesel pump and I was driving on Mway for maybe 10 mins before pulling off and stopping at a shop when I noticed steam coming out from under bonnet. when I opened it up I found things well soaked even evidence of some spray over to air box and on side of battery so it must have been spraying out for a few miles before I saw it.

thanks for your input

Chris

[evilally]

I'd start with the easy stuff, disconnect and clean the connector for the needle lift sensor with some WD40 in case it got some coolant in there. It would also be interesting to know if you still have the rev counter issue if you left this sensor disconnected.

[DublinChris]

I'd start with the easy stuff, disconnect and clean the connector for the needle lift sensor with some WD40 in case it got some coolant in there. It would also be interesting to know if you still have the rev counter issue if you left this sensor disconnected.

Always good to start with the easy stuff

will take a look in the morning

[DublinChris]

I would check the connector to the needle lift sensor. This is the injector with the wire coming from it, the plug for it is right next to where you had the coolant leak. If you unplug this sensor, the pump will default to full advance, and the engine management light will come on. I wonder if this is the problem in the first place, as I believe the ECU can use this information to feed the rev counter (in addition to the crank sensor). If it was giving spurious readings, would it cause an issue with the rev counter? What diagnostic tool is the mechanic using? I wonder if a Lexia would reveal more?

Well I disconnected the connector and cleaned it but alas problem has not gone away -if anything things are getting a bit worse. I did think initially on Thursday that there was an improvement and eml stayed off until I was pulling into drive near midnight on Thursday after a full days driving. Well Friday I had some good periods and then in afternoon was stuck in city traffic for quite a long time (outside temps had gone up to 12degrees c) and eventually the temp gauge went to the point were fans cut in - at the same time the eml light came on and stayed on until I could pull over and turn engine off. I restarted and light was out. I have noticed as well since then that engine can be rougher and the times when you can hear the pump advancing and the engine making the louder "diesel" noise have become more frequent. the rev counter still has its mad moments at start up - but not every time.

The main times when the eml will flash seems to be when I let revs drop to 1K and 1.5K as in slowing to a stop at traffic lights etc but once I give it a rev up to 2K the light will go out. On Mways etc and normal driving it stays off with higher revs.

Really stumped at this stage as to what is at root of problem. Still cant help feel that it all kicked off with the coolant leak last Saturday - or maybe it is just a coincidence?

All help appreciated

Chris