won't start, strange set of faults!

Evening

My sisters trusty c3 remains ultra reliable!

Looking at a neighbors c3 which won't start, noticed the in tank wasn't running.

2004 1.4 8v petrol

Checked it had voltage, it did but but only 10v and it had voltage whenever the bsi was still on. Weird.

Supplied 12v to the in tank pump and it got the pump running but still wouldn't start.

I have lexia and ran it, won't connect to the injection part of the ECU.

I'm a bit confused about it having voltage at the wiring harness for the in tank pump whenever the bsi is on and only 10v. And why it won't fire when the pump does run with a 12v feed.

I've spent hours searching online, tried a bsi reset, checked for a faulty wire from the ECU as suggested on here but I'm stumped!

Any help would be great! She doesn't have much money and I'd really like to sort it if possible! Thanks!

Hi Alexr89

Alexr89 wrote:I have lexia and ran it, won't connect to the injection part of the ECU.

I can see there could be 2 possible reasons for this.

You lexia is not up-to-date enough to detect the ECU

or

Your ECU is not powered / fried.

There is a topic reply on Lexia and OBD diagnostics on a Citroen C3 called 'Lexia showing a question mark for ECU'. Which may be the same problem you have.

Alexr89 wrote:I've spent hours searching online, tried a bsi reset, checked for a faulty wire from the ECU as suggested on here but I'm stumped!

Fix the ECU reading by lexia and then you can diagnose further.

Thanks for the reply I'll check that out!

As far as I know lexia is fine as I've ran it on a few cars newer than this one with no problems.

Thanks

Then a non powered up ECU or one that is fried or damaged would tie up with the reason the engine won't start.

Start with the easy stuff, check fuses in the engine bay (bsm) and the cabin (bsi)

You can also remove and refit the ecu connectors to check for contamination on the connectors.

Hi Alexr89

As you've got access to two C3 I would plug your Lexia into the good one and see if you can read the settings that you can't access on the broken one.

Thanks yeah works great on the other c3

Have checked all fuses, have refitted the ECU plugs a couple of times but nothing.

It's just odd that it gets 10v when the bsi is still on, is expect it to have no voltage. I've read about a dodgy wire from the ECU but nobody has took a pic or even explained where it actually is but as far as I can see the wiring appears to be present and correct.

It'll probably end up getting scrapped which is a shame but I don't think she'll be able to go for the buy parts and hope for the best approach

How/where are you measuring the 10 volts?

Is this across the pump terminals or between the +ve and a ground on the car chassis?

Just asking as 10 volts sounds like the sort of spurious voltage you get with a faulty earth and a high impedance multimeter.

You could try the measurement with a bulb across the pump to give some load on the circuit?

Alexr89 wrote:I've read about a dodgy wire from the ECU but nobody has took a pic or even explained where it actually is but as far as I can see the wiring appears to be present and correct.

Are you talking about the throttle body fault, throttle pedal wire? Maybe not, because this won't affect the ECU power or diagnosis.

Alexr89 wrote:Have checked all fuses,

There is checking fuses and just looking to see they are ok.

You need to remove the fuse, test it with a meter and inspect it for corrosion

F8 and F15 in the BSM - engine bay fuse box.

Alexr89 wrote:Thanks yeah works great on the other c3

Interesting, do you know what year the both C3s are (the RPO from the door shut) would help, and do you know your lexia version number? or diagbox if you are using that?

Arfur Dent wrote:

Alexr89 wrote:I've read about a dodgy wire from the ECU but nobody has took a pic or even explained where it actually is but as far as I can see the wiring appears to be present and correct.

Are you talking about the throttle body fault, throttle pedal wire? Maybe not, because this won't affect the ECU power or diagnosis.

Alexr89 wrote:Have checked all fuses,

There is checking fuses and just looking to see they are ok.

You need to remove the fuse, test it with a meter and inspect it for corrosion

F8 and F15 in the BSM - engine bay fuse box.

Alexr89 wrote:Thanks yeah works great on the other c3

Interesting, do you know what year the both C3s are (the RPO from the door shut) would help, and do you know your lexia version number? or diagbox if you are using that?

Hi, no the fault I read about was directly related to the ECU, possibly a brown wire but I haven't been able to find the thread again.. might not have been on here actually but the description after discovering the fault was vague to say the least.

When I say I've checked them I mean pulling them, visually inspecting them and checking for continuity. Was 10v at the fuse for the fuel pump too but only when the bsi was on.

I'm not sure which version Lexia it is, the laptop I use for diagnostics is in my unit. I don't think my lexia or the cable is at fault though, I've used it three times since I had this C3 plugged in.

2004 & 2006 is all I know at the min without getting the RPO numbers.

I keep coming back to it having 10v at the in tank fuel pump plug only when the BSI is on, it's either electrical or an ECU problem.. the latter being less likely I'd have thought.

It has to be affecting more than the fuel pump circut as it would have fired when I hooked the pump up to 12v unless I'm missing something!

Alexr89 wrote:2004 & 2006 is all I know at the min without getting the RPO numbers.

Your lexia reads the ECU on the 2006 but not the 2004?