All Things V6...

[KP]

650+miles from my little HDi90 Donk at the minute and mostly short trips with only the odd 10mil jaunt on a motorway to break it up!

[KP]

Im surprised the fuel doesn't go off in the tank David with so little miles being done!

Do you keep it low on fuel at all for that reason or just keep topping it up?

[DHallworth]

I tend to put 20l in at a time over the winter. It does get run over the winter, started and run for an hour or so at a time, warmed through properly and revved to clear it out.

The road we live on is a country lane and never gets gritted in the winter so if we get a nice dry day when the roads are clean and dry it very very occasionally does a couple of miles. It never sees a main road from September onwards to avoid the salt

David.

[DHallworth]

I'm also not convinced that petrol does actually go off to be honest.

The C5 I got from Luke has the same petrol in it now that it did when it was laid up 8 years ago... It runs beautifully on it... (When I can get the thing to start!)

David.

[CitroJim]

That is a very special XM David, thanks again for the drive in it It's done nothing to tempt me away from XMs

I know. I have an identical one but for condition and I just get drawn closer to it with every trip I do in it. Brilliant car...

Sorry I missed you at Wetherby My blog will say why in a while.

So, what's the latest news of the C5 then David? It still seems to be a challenge...

[KP]

TBH in more sensitive vehicles I know it goes off and suffers, especially in heat. I laid up more coop for 4 weeks nearly in a nice and hot 2004 summer while i went and did some eastern travels.

I'd let it run low before going and put 30litres in it before i left of shell Optimax.

Came back and it cranked and fuel was going into the rail but took a booster pack to finally get going and spluttered into life. Getting to the nearest shell station about 4 miles away was fun as it idled quite roughly and didn't like being on boost much at all!

Topped up with optimax and on the journey home after a mile or two could feel it improve but not massively. I ran that tank right down and then filled up again with some redex and that seemed to do the job.

The LPG never suffered the same issues though when it was done. It would start up just fine when force started on LPG when laid up for ages...

[DHallworth]

Right... I went to have a look at the C5 again tonight...

I cleared all the fault codes and then tried to start the car. It started running on around 5 cylinders or so, let me rev it to around 2500rpm where it stuck for a few seconds and then quickly faded away and died.

After doing this there was a few fault codes stored again:

permanent fault - inlet manifold pressure sensor - this error was stored at around 1800rpm
permanent fault - engine speed sensor signal coherence
permanent fault - engine speed sensor signal
permanent fault - air con pressure sensor short circuit to earth
remote fault - intermittent fault - vehicle speed sensor coherence

I then had a look at the parameter measurements and there was something a little odd that caught my eye on the ignition coil charging times:

1 - 1.877
5 - 2.048
3 - 2.048
6 - 2.560
4 - 2.731
2 - 2.048

My understanding is that the charging times for all of the coils should be the same. 3 of my 6 coils are identical but the others are somewhat out of sync. I'm wondering if I've got a few dodgy coils.

Anyway, it's my week on call and my work phone's just started ringing so that's all the fault finding I can do for tonight.

David.

[Hell Razor5543]

I would be inclined to first give the coil connectors a good cleaning, using a proper electronics cleaning fluid. Dirty connections can cause weird problems.

[CitroJim]

I'd be inclined not to worry about the coil charge times David, I've seen much the same on an old-school ES9 without too much apparent detriment...

I might have missed that you have but i take it the tank was drained of petrol and refilled with nice new stuff. I'm wondering if the old petrol might have gone off and gummed things up and is now causing fuel starvation leading to your latest issues?

Sorry if that's old ground...

[DHallworth]

Jim,

Because it started and ran so well with the old fuel in it the first time I must admit to being slightly lazy and not bothering to drain the tank and change the fuel.

Will give it a go and treat it to a new fuel filter when I get the time. The Freelander needs a polyurethane bush kit fitting to it before the C5 gets any more attention.

David.

[Ben82]

David,

Before you buy a fuel filter, ensure it has one. According to service.citroen.com my VIN's diagram for "Securing piping fuel filter" lacks the actual filter. I'll probably do a visual inspection on mine when I do my service to make sure service.citroen.com is correct.

It's probably also worth graphing the engine and vehicle speed sensors to see if it's giving anything out of the ordinary?

Ben

[DHallworth]

Thanks Ben, just checked and sure enough there's no fuel filter on this one either.

I bought a GPS disc for it on eBay the other day. Was listed as a genuine item, 24 hours after I'd won it eBay wrote to me advising not to pay for it as the seller has been removed from eBay.

It's just turned up this morning in the post and it was a copy I received. Have put it into the drive in the car and it keeps ejecting the disc so am not sure if it's a bad disc or a fault with the drive. I can hear the disc spinning and the laser moving in the drive but the arrows on the screen for the navigation are greyed out.

Will grab 20l of fresh fuel for it this afternoon and see what happens.

David.

[Mandrake]

Right... I went to have a look at the C5 again tonight...

I cleared all the fault codes and then tried to start the car. It started running on around 5 cylinders or so, let me rev it to around 2500rpm where it stuck for a few seconds and then quickly faded away and died.

I think I mentioned it earlier but if not put a fuel pressure gauge on the fuel rail. I'd be inclined to agree with Jim that there could be something bad in the tank that has blocked the line. Running for a bit with a misfire then dying away and stalling sounds just like fuel starvation from a blocked fuel line or pump problem etc. The fuel pressure gauge will give you a definitive answer very quickly.

After doing this there was a few fault codes stored again:

permanent fault - inlet manifold pressure sensor - this error was stored at around 1800rpm
permanent fault - engine speed sensor signal coherence
permanent fault - engine speed sensor signal
permanent fault - air con pressure sensor short circuit to earth
remote fault - intermittent fault - vehicle speed sensor coherence

Is this with the borrowed MAP sensor or the new one that has presumably arrived by now ?

Have you checked the TPS reading on the Lexia through the range of motion of the throttle ? The voltage should go smoothly from about 0.5v to 4.8v. (Rough figures from memory) Sometimes a MAP sensor fault can be logged due to a TPS fault as the ECU does consistency checking between the MAP, TPS, and engine speed readings. (For a given engine speed and throttle opening it has a rough idea of what the MAP reading should be, if its way out it will log a fault, which means faulty TPS or engine speed data could cause the same MAP sensor fault)

Engine speed sensor signal fault suggests the crankshaft sensor is not working properly, and could easily be the cause of the problem. There's no chance the wires to that were disturbed ? (I think I asked about this possibility earlier)

If the fuel pressure is OK the crankshaft sensor signal is my second bet after looking at all the above fault codes, especially considering the bogus engine speed reading you were seeing from the gearbox ECU a few days ago.

Vehicle speed sensor coherence has me baffled - the vehicle is not moving so how can it know!!

I then had a look at the parameter measurements and there was something a little odd that caught my eye on the ignition coil charging times:

1 - 1.877
5 - 2.048
3 - 2.048
6 - 2.560
4 - 2.731
2 - 2.048

My understanding is that the charging times for all of the coils should be the same. 3 of my 6 coils are identical but the others are somewhat out of sync. I'm wondering if I've got a few dodgy coils.

Anyway, it's my week on call and my work phone's just started ringing so that's all the fault finding I can do for tonight.

David.

I agree with Jim - don't get hung up on the coil charge times, they might cause a misfire but the variations you're showing won't stop it running, nor would they allow it to start, run for a while then stall, so they're very likely a red herring. I ended up replacing my coil pack while looking for a misfire based on different coil charge times, all for nothing, the new coil pack had similar but different variations to the original and the original was not faulty!

By the way have you done basic checks like checking for spark ? Do you have any inline spark testers you could connect to see if the spark is stopping when it stalls ? Remember the Lexia can manually fire both ignition coils and injectors for testing too...

If its still not working in a few weeks time I'd be happy to pay a visit and see if I can help figure out what's wrong with it. It's got me intrigued, and I have amassed an array of diagnostic tools in my bid to get my V6 working properly that may help including fuel gauge, inline spark testers (two varieties, neon and spark gap) a small digital scope, an injector balance tester and a few other goodies.... Plus I'm sure I have the full diagnostic data, wiring diagrams etc for that model in Citroen Service Box, if you don't already have access to that...

[Ben82]

Vehicle speed sensor coherence has me baffled - the vehicle is not moving so how can it know!!

I thought maybe it's the other way around? i.e. the ones for the ESP are saying the tyres aren't rotating, the gearbox is saying it's in Park, yet the vehicle speed sensor is reporting it's moving? Could it be that, or am I over complicating the way the ECU works out how to throw these errors?

[Mandrake]

Vehicle speed sensor coherence has me baffled - the vehicle is not moving so how can it know!!

I thought maybe it's the other way around? i.e. the ones for the ESP are saying the tyres aren't rotating, the gearbox is saying it's in Park, yet the vehicle speed sensor is reporting it's moving? Could it be that, or am I over complicating the way the ECU works out how to throw these errors?

I don't know how its determined Ben, I'm assuming that its the ESP system comparing the wheel speed sensors used for the ABS, against the road speed sensor in the gearbox (in the diff in the gearbox which is measuring the average of the front left and right wheel speeds) and deciding that there's a mismatch.

My complaint with the fault code is that he's cleared the codes but that one has come back without the vehicle even moving... so how did it decide that the speed sensors were giving incoherent data ?