Peugeot 806 2.0i turbo (Xu10J2TE) - died while driving, wont start, no gasoline, no spark

[tortuga]

My Peugeot 806 suddenly died when driving and wont start.
I have tired/checked the following:
- Gasoline pump wont start when turning ignition on
- When cranking the starter motor will crank but there is no spark
- Replaced double relay, still the same
- Tried to connect 12V directly to the fuel pump (through double relay plug), the pump starts then but engine wont start
- Tried to go around inertia fuel switch, remove it, reset it, just join two cables going to it, nothing changes
- Immobiliser light on the dash bliks when key is not inserted, stops blinking when key inserted and ignition is on (so probably immo is OK?)
- Tried to connect with Diagbox to ECU but says no connection was made (could be because Diagbox is installed inside VM? and not the car issue? Would need to check it with other car)

I plan to check the following in the next few days:
- Check if there is 12V supply to double relay plug when ingition is off
- Check if there is 12V supply to double relay plug when ignition is on
- Check if there is 5V supply to any sensor (ie airflow) after ignition is on
- Check 12V supply to ECU itself
- Check if diagbox is working OK, just need to find another Pug or Citroen near me

I suspect one of two things, or the 12V supply to ECU is gone or insufficient (could be 12V+ side issue or ground side issue) or ECU itself just died.

Any ideas on what more to check and how?

[PaulC5]

Check all the fuses including the maxi fuses.
Check the crank shaft sensor.

[tortuga]

Checked the fuses 3 times already
Crank sensor seems like good hint. Do you know what resistance should it give by default?

[ekjdm14]

Crank sensor is a fair call, but the lack of fuel pump prime is suspect if I'm reading you right. The fuel pump should run for a second or two and then stop when you key on so that missing coupled with the lack of communication has me suspicious.

When you switch the ignition on, do you see the EML/CEL (engine light) on the dash? I'm wondering if the ECU is missing a key-on supply.

Not sure on crank sensor resistance, but if it's a 2-wire type I'd check for a low (circa 3-6v) AC output from it during cranking.

[wheeler]

Crank sensor is a fair call, but the lack of fuel pump prime is suspect if I'm reading you right. The fuel pump should run for a second or two and then stop when you key on so that missing coupled with the lack of communication has me suspicious.

Agreed, you should still get an initial prime of the fuel pump if the crank sensor is faulty.

From memory inductive type sensors should be around 350-400 ohms however resistance & voltage checks are not a reliable way to check an inductive sensor, scoping it is the only proper way IMO.

Yes, 5v & 12v supplies need checked next.

[tortuga]

I think we can discard crank sensor tests for now then, there is no initial fuel pump prime.
Fuel pump in this car was quite loud and you were able to hear it clearly when turning ignition on, now it is not working, im 100% sure.
When I supply 12V directly from battery to Pin 9 (this supposedly goes directly to the pump) on the double relay plug the fuel pump starts, you can hear it working as before but there is still no spark.

As for the K light on the dash the light bulb died few weeks ago (when car was working normally), so it is not turning on right now, I will change the bulb and see if the light comes on or not.

[PaulC5]

If the crank sensor is working you might also get the rpm shown as you turn it over on the starter.
To check if a fuel problem you could try using easy start to see if it will run for a bit.

[tortuga]

Its not only fuel problem, there is no spark on top of that, so I can spray as much easy start as I want and it wont start.
If everything goes well I will be doing some additional tests tonight, I will keep you updated on the progress.

[ekjdm14]

As for the K light on the dash the light bulb died few weeks ago (when car was working normally), so it is not turning on right now, I will change the bulb and see if the light comes on or not.

That's interesting, yes I'd agree check/replace the bulb and see what happens there. I'm wondering now if this could be an ECU capacitor/corrosion issue, be very interested to see if the bulb is in fact burned out as that'd be pretty rare unless you were driving with the light on for a long time & there's often no such thing as a coincidence with cars, the light going AWOL could've been an early sign of a deeper issue with either the ECU or it's connections.

[tortuga]

@ekjdm14 you were right, its not the bulb, I have replaced it, the K light is not coming On when ignition is ON. Its dead.
I have also made additional tests today.
Here is what I got:
Checked again all the under the driving wheel fuses and engine fuse box.All were fine including fuse no.5 and no.6 in the engine bay. Also there was 12V from battery on both fuses in the engine bay.
Checked pins 14, 8 , 5 on the double relay plug for permanent 12V even with ignition off, all OK there is permanent 12V.
Checked pins 2,3 on the double relay plug for 12V when ignition on, again 12V OK.
Checked pin 18 on ECU for permanent 12V+,no problems at all 12V OK
Checked pin 27 on ECU after ignition is on, no problems 12V registered there.

So seems that ECU is getting 12V to wake up but its not doing anything. Is it simply dead? Could I just swap ECU with another one for the same engine from scrap yard? I suppose I would need to deactivate the immobilizer for it to work with the car right?

[wheeler]

What about the ECU earths? ideally load test them.

What wiring diagram are you using?


If you use a 2nd hand ECU you will either need to have the immo deactivated or you would also need the matching CPH unit & a working key all from the same car.

[tortuga]

The diagram I use is the one provided by SEDRE...I would attach it to the post but have no idea how to do it here...wait just found it...attached.

But only swapping ECU even if the immo is not deactivated should at least let me connect to ECU with diagbox and the K light should come on on the dash right?

[tortuga]

Could the grounds be pins 24 and 14 on the diagram?

[RichardW]

Yes, that looks right

[tortuga]

I have checked all the grounds and pins 14,24,19 and 47 there are no problems, ECU receives 12V+ and 12V-

But I have discovered something, if I move double relay plug a little Im able to hear one of the relays to engage and the K engine light on the dashboard turns on.Probably the contacts on the plug are wobbly and they do not make good connection with the relay.
Also after moving the double relay I got the spark when cranking! Which means ECU is alive...probably. Still no sign of fuel pump turning on.

I will try to get the K light on the dash to turn on again and then will connect with Diagbox, to see if I can get any info from ECU now.