C5 X7 not starting (again)

[wurlycorner]

I'm not familiar with the systems on a diesel X7 at all, but applying general knowledge of 'typical' fuel injection systems... This sounds like classic symptoms of either the main fuel pump relay or ignition switch being faulty, or whatever signal the ECU looks for in order to determine that the engine is 'running'.

Basics need to be checked/confirmed first as others have said;
Check all earths and all connections on the relevant circuits for being clean/secure and for continuity.
If they're ok the likely causes are then ignition switch, main fuel pump relay or the ECU failing to recognise that the engine has started.

This is based on the basic principle/sequence of a fuel injection system being;
Ignition on - fuel pump is energised for a brief moment, to build up pressure in the rail
Key switch to start - fuel pump relay is fed directly from the ignition switch, in order to energise the fuel pump while cranking
Key switch back to ignition - fuel pump relay is fed/maintained by a signal from the ECU so long as the engine is running
Key to 'off' - ignition feed to the main ECU is removed so the fuel pump relay drops out, causing fuel pressure to be lost (may also remove feed to the +ve contact side of the fuel pump relay depending on the circuit design on the car)


Does this tend to happen after the car has been used and then parked up for a short while? If so, that to me would suggest the main fuel pump relay - (the coil or contacts go open circuit as they warm up although tend not to drop out during use, but do then fail to work on 'restart')

If it's also (or only) on a proper 'cold' start, then that would suggest to me that the ECU is not recognising that the engine is running, so it doesn't take over supplying a feed to the fuel pump relay.
Not sure what the C5 uses to determine engine running. Some cars use oil pressure, some use alternator charging, or more modern cars may use who knows what (I dunno, I'm used to working on stuff from the 90's )

The ignition switch could sit in either category, but if that's faulty you would normally/may notice the instrument panels go out at the same time.

[RichardW]

I don't think there's a low P fuel pump on these....

Re the discussion about the software above - the interface is the same, these days you just start Diagbox. Once the car is connected, you can chose Diagbox or Lexia (or Peugeot Planet) to interrogate it. Lexia / PP run within the DB shell. For anything later than Xantia it will be Diagbox for preference - Lexia will probably talk to some of it, but will have limited functionality. Diagbox 7.15 should talk to an 08 X7 no problem.

[qprdude]

All good advice but I'm at a loss how a fuel problem can sort it's self overnight. Yes, this has happened four times now, and after the car has been stopped for a couple of hours. As for the advice on checking for faults, I'm sorry, but you might as well be talking Greek. I wouldn't have a clue where to start as it's over 40 years since I did any meaningfull repairs on a car engine. The days of the carburettor and distributor, points and plugs kind of stuff, with the occasional rocker cover gasket, and once a timing chain on a Hillman avenger , but I'm too old, too idle and too thick to even attempt to get into anything more involved in oil change and filters nowadays.

[wurlycorner]

All good advice but I'm at a loss how a fuel problem can sort it's self overnight.

It won't be the fuel itself that is the problem, it'll be something electro-mechnical, with the fault being susceptible to changes in temp/humidity etc. (the cause of so many car gremlins coming and going intermittently).

I'm too old, too idle and too thick to even attempt to get into anything more involved in oil change and filters nowadays.

And I doubt there's anything 'thick' about you and nothing wrong with not wanting to get your hands dirty anymore, either - that's why car mechanics were invented! (unfortunately many of them these days don't have a (-expletive removed-) clue what they're doing though, if it gets more involved than changing brake pads and oil filters... )

[citroenc5mad]

Hi this sounds very similar to the problem I had.

It would crank to start then engine would tick over for a split second then stop, this would happen on a hot or cold engine.
I was tralling the net and posts on here.
All lead me to fuel filter, on replacing the fuel filter, I notice the fuel reheater looked a bit dodgey, so ordered a new one and no problems starting since unless I used a cheap fuel from the supermarket. Only once and the same problem arose. Now I only use 1 garage and bo problems, for a few months now.
Have to say mines a 1.6 hdi tho so not sure if yours is the same.

So maybe the fuel heater might be worth a look, it cost about £50 incl. vat.

[wurlycorner]

I don't think there's a low P fuel pump on these....

Couldn't reply to this last night after my other post, but intended to say...

Yep fair do's, I did say I didn't know anything about x7's - I've never even studied a diesel Hdi set up, so quite possible/probable I'm talking out of my arse
But... I've looked a few things up since.
My Citroen wiring diagram book only covers the 'comfort' systems, so that's no help.
Checked Haynes and of course it's bloody useless - the 'typical starting/charging circuit' doesn't include anything about a feed to the fuel injection system (although it does show some relays in the Bsi and engine fuse box) but the description of the fuel/emissions system elsewhere for diesels (which says it's applicable to 2.2, 2.0 and the 1.6) does say that the system has a low pressure fuel pump, so...

[qprdude]

Had a visit this morning from James (Hellrazor) who gave the X7 a good seeing to with his Diag-box. Threw up a few fault codes. Cleared those that would clear and checked again to see what had come back. Then went for a short drive to see if anything else turned up.
I don't pretend for on e minute, to understand much of what was discovered but two of the three returning faults seemed to be unrelated to the starting problem. One was a TPM fault, which has been evident for some time, and another was a suspension fault but I'm not sure what it was.
The important fault, as far as I'm concerned was "injector fault" which seemed to suggest a fan fault, either one cooling the ECU, or the engine cooling fan(s)
I'm going to try to upload some photos of the fault logs that James photographed on his laptop screen, to see if anyone can shed any more light on the test results. Only the "fan" problem for the time being. The first should be the initial test. The second is after clearing the fault log. The third is a re-check with more detail, after taking the car for a short run.
Sorry, but that's a clear as I can make it. I hope \I have them in the right order

[Stickyfinger]

Complete Engine fan failure (motor buggered) did not generate a fault on mine...the relay was/is good so maybe why it did not ??
.....(u can change the relay without taking off the bumper btw)

[wurlycorner]

http://www.datsc.com/tabid/122/OBD-Erro ... fault.aspx" onclick="window.open(this.href);return false;

Generic OBD Error Code Details for P0483
Fan Rationality Check

What does this mean?
OBD Code P0483refers to
The electric cooling fan is controlled by the powertrain control module (PCM) through the cooling fan relay based on inputs from the following components: - The engine coolant temperature (ECT) sensor - The intake air temperature (IAT) sensor - The A/C selector switch - The A/C refrigerant pressure sensor - The vehicle speed sensor (VSS)
The PCM controls the cooling fan by grounding the cooling fan control circuit which turns ON the cooling fan relay.
The cooling fan relay will be commanded ON when the following conditions are met: - The engine coolant temperature reaches 106°C (223°F) or more. - The A/C clutch requested. - The vehicle speed is less than 38 MPH.
The cooling fan relay will be commanded ON regardless of vehicle speed when the following conditions are met: - The engine coolant temperature is 151°C (304°F) or more. - The A/C refrigerant pressure is high.
The cooling fan may be commanded ON when the engine is not running under a fan run-on conditions described in the electric cooling fan general description portion of the service manual.

Symptoms
Possible sumptoms of OBD code P0483
- Engine Light ON (or Service Engine Soon Warning Light) - Engine overheating

Causes
Possible causes of OBD code P0483
- Fan control relay harness - Fan control relay connector - Fan control relay - Cooling Fan The Error code is generally activated on detection of the following conditions: The P0484 code is detected when the PCM detects that the commanded state of the driver and the actual state of the control circuit do not match.

Possible Solutions
- Replace the malfunctioning fan control relay - Replaced cooling fan

I don't see that an 'irrational' fan can be related to the starting problem though, unfortunately.

[xantia_v6]

I don't see that an 'irrational' fan can be related to the starting problem though, unfortunately.

Corroded connections in an ECU (or other) connector?

[vborovic]

@ Hellrazor - don't know how tech/PC-savvy you are, but it helps to install a PDF printer (CutePDF or similar) on the diagnostic notebook and then you can "print" the DiagBox output to a virtual printer, which will create a fine PDF (indexable, selectable text), which you can then share via USB, e-mail, etc ... it helps a lot when you're on the go ... no need for phone photos and other "manual" methods ... of course, this is not only for James, other members can make use of this tip as well ...

[Hell Razor5543]

Thanks for that tip, I will look into it.

I know that my knowledge with Diagbox is minimal, but what I hoped to do was to find any faults (if any) that would not clear, as I felt that these were most likely to be relevant. There are, in total, three. Rick has already posted one, there is another in the Suspension tab (which suggests that something isn't getting a speed input), and the other is in the TPM system (well, there are two here, one is speed related, and the other is a non responsive sensor, that won't say what pressure it can see! Bit weird, this one, as Rick advised me the O/S/F has an issue, but, according to Diagbox, the N/S/F isn't talking).

There had been other faults when we started (and we took screen shots), but these cleared when asked to, and have not returned (if they do, we can identify them due to said screen shots).

[qprdude]

Second permanent fault. As before,first, second and third readouts. (I hope)

[wurlycorner]

and the other is in the TPM system (well, there are two here, one is speed related, and the other is a non responsive sensor, that won't say what pressure it can see!

What's the TPM system and what are the details on the 2 faults related to it?

I wouldn't expect to see this starting problem as a 'permanent' fault code, since it's an intermittent fault.

What were the intermittent fault codes that were cleared?

[Hell Razor5543]

TPM is Tyre Pressure Monitoring. The injector fault is an intermittent one.