Alarming engine cut out!

[dowen]

Has anyone any ideas!

My xantia v6 98 cuts out dead, about five minutes after starting from cold, and then it takes several turns to get it going! feels like fuel starvation!
From then on its perfect and runs just fine, It only happens from cold every day. Has anyone had this problem?

Thanks, Dave.

[CitroJim]

That's a new one Dave

It's either loosing sparks or fuel. If it can be reproduced every time I'd be tempted to initially connect a voltmeter or a small test lamp across the fuel pump and watch it to see if the fuel pump cuts out at the same time as it stops.

If not, repeat the same test for the ignition coils.

Does it happen when the engine is under way or when just idling for that time? If when idling it may be connected with the idle control valve but this would not be the cause if the car is under way when it happens.

If you see volts lost to the fuel pump or the coils or both then the problem may be with the immobiliser transponder. 5 minutes rings a distant bell somewhere in my mind.. I must think more.. Does the transponder light in the tacho come on when the engine cuts?

How hard is it to start the engine after it has cut out exactly?

[wheeler]

The transponder system causing the engine to cut out ?? the key only needs to be regognised for initial starting, once the engine is running you can take the transponder away & it will still continue to run till you switch it off. The transponder doesent cut the fuel pump either, it just stops the injectors switching & sometimes stops the spark trigger pulse depending on the injection system.
If you are losing the feed to the fuel pump and/or coils the first thing i'd be thinking is double relay.

[dowen]

Thanks Jim, doesnt the fuel pump get its 12v only with the engine running? I started it this morning, let it run on tickover, and after about 5 mins it just stopped , no splutter, just as if I had turned the key off! If it happens when moving the speed of the moving car gets it going quite quickly, but what usually happens is Im halfway round an island or in the middle or a junction! It takes a fair bit of starting, as you turn the key the engine gets gradually faster and faster as if its fule starved, and then the engine takes over from the starter, if you know what I mean. ther is no sudden burst into life.

It feels like the fule rail is empty! Thing is it only does it once, and its fine for the rest of the day!

In the morning as soon as it cuts I will check the fuel rail. Let you know.

Thanks for getting back.

Dave.

[DickieG]

I can't recall off the top of my head but is the fuel pressure regulator on a V6 attached to a vacuum pipe? If so check for vacuum leaks as well as checking the actual fuel pressure. I take it you can't hear any grumbling from the fuel pump under the rear seat?

[dowen]

I put meter across fuel pump this morning, with the engine on tickover 14v till engine cut at exactly 5 mins.I was hoping fo 0 volts to come first but engine cut and 0v at same time! so I checked for fuel pressure at rail, and theres plenty.
It seems to me that there is some staged transition from cold to hot involving various sensors, and one of these sensors is sending a wrong signal and cutting engine, it seems to be happing about the time the stat opens! + or - 10 seconds off 5 mins from start.
Before I dare take it on the road now I have to run it through its cutting out phase, and its fine for the rest of the day.

Would a diognostic pick this up?

Dave.

[DickieG]

Would a diognostic pick this up?

Possibly but better than reading any recorded codes will be to view 'data-stream', the flow of information between the ECU and sensors etc as a fault will only be recorded if a sensor steps outside of pre-set parameters, obviously a Lexia will be the best tool to use for this.

[CitroJim]

Dave, this is most odd. I can't think of anything that distinctly changes after 5 minutes of running and this seems to be quite a precise time to failure...

A Lexia showing a live data stream may be helpful and I'd be inclined to be watching the outputs of the MAP sensor and the coolant temperature sensor. The latter I'd be inclined to change as a precaution anyway as I've heard of them doing strange things at some temperatures. As the sensor warms in the coolant it may hit a dodgy part of it's characteristic and make the ECU think either the engine is very hot or very cold thus stalling the engine. On a restart it's then past its dodgy area and all carries on happily...

That's just a guess at this stage but luckily the sensor is not dear and easy to get to to swap - it's the only sensor that is on the V6

The inlet air temperature sensor is connected and snug in its slot on the air box isn't it? Worth a check as these can become dislodged on removal/replacement of the air box.

[dowen]

Thanks Jim, Tomorrow I run it with sensor un-plugged, see what happens.

Dave.

[CitroJim]

Thanks Jim, Tomorrow I run it with sensor un-plugged, see what happens.

It won't run with the coolant temperature sensor unplugged Dave...

That was what i was trying to say above. At a certain temperature the sensor may be going open or short-circuit and causing the problem. Replacement is the only way really to test it...

[dowen]

Well last night I swapped the sensor from my XM, started the XM from cold, (2ltr 16v) and hoped it would cut after the five minutes, of course it did not,it ran perfectly! Well I thought it cant be the sensor.

So this morning I started the Xantia from cold and waited for it to cut out, and waited, and waited! Success, simple thing cost me nothing, couldnt be more pleased! Thanks Jim for your help.

[CitroJim]

Dave that's excellent news