Xsara Picasso won't start

[Vuk1987]

Greetings guys,

I have a problem with Xsara Picasso 1.6 16v (NFU/ TU5JP4 engine).
Engine cranks, but wont start most of the time. I have been struggling for almost a month now. First, the fuel pump was dead (got that from not hearing it when I switch on the ignition). Replaced it with a used one, and now the engine barely starts. I also have LPG installed which complicates things. Now, most of the time, when engine is cold, it will start after a lot of cranking. When it starts it works crappy. When it's hot, it won't start no matter what I did, except if I unplug the coolant temperature sensor. When the engine is off, and I unplug the coolant temperature sensor, it starts fine, mostly. The sensor is not a problem, since I firstly replaced one a year ago, and again yesterday thinking he's the problem. However, nothing changed. I read the fault codes with Lexia and I will post them here. There are codes caused by me driving with a coolant temperature sensor unpluged, but the ones that I I have my eye on are codes P0202, P0204, P0203 and P0201. I also have a picture of the diagram from the Sedre. If I've read right, wire from the injectors (parts 1331 to 1334) goes to PSF1 point 16. Is it a fuse, a relay, something else I have no idea, not an electrician. Any suggestions? Check replace a fuse/relay? Bridge something together (make a bypass)?
I have already been to a mechanic, he has no clue. I turned off the LPG by pulling out the fuse. Thanks in advance guys

[wheeler]

First thing you need to do is see if there is a power supply at pin 16 of the 16 way black connector at the under bonnet fusebox when its cranking over but not starting.

Once the engine starts does it run normally without any misfiring?

I notice the coolant temp is showing as -40 on some of the screens, is this when it its unplugged?

[Vuk1987]

It doesn't run quite normally, it misfires after start and chokes from time to time. Also depends on whether I'm running it with or without temp sensor plugged. I will check that thank you. If there is no power supply, what then?

[Vuk1987]

"I notice the coolant temp is showing as -40 on some of the screens, is this when it its unplugged?"

Don't know, I ran lexia on engine off

[wheeler]

-40 is the default value the ecu sees when the sensor is open circuit.
Have you ruled out an ignition coil pack fault? Very common on this engine.

[Vuk1987]

Have you ruled out an ignition coil pack fault?

Replaced it few years ago, but It's possible of course. Is there a way to check it without replacing it again?

[xantia_v6]

I would suspect low fuel pressure, perhaps a failing pump or blocked fuel filter.

[Vuk1987]

I would suspect low fuel pressure, perhaps a failing pump or blocked fuel filter.

Interesting thing is that I replaced it previously to this problem, a few weeks ago (the pump), but the machanic put in the used one, not new. Is there a way to check the pressure? What should be the pressure (the value)?

[Vuk1987]

I also replaced the fuel filter righta away, since I suspected on it first, although I change it regularly.

[wheeler]

Have you ruled out an ignition coil pack fault?

Replaced it few years ago, but It's possible of course. Is there a way to check it without replacing it again?

I use these > https://www.ebay.co.uk/itm/111584294839 ... BMhL7nn6Zj

There is normally enough slack on the harness to allow them to be fitter in between the spark plugs & coil pack.

[Vuk1987]

Ok 12v on a 16-th pin on a 16 way black connector on under bonnet fusebox. Now I managed somehow to start the engine, but after a few minutes on running idle, the fan turned on, and warning about engine temperature and then it went off again and showed normal temperature. I guess the temp sensor is loosing contact. Any ideas now? I'm afraid it's multiple things

[CitroJim]

I'd be replacing the temperature sensor before doing much else if it's still showing= -40 on the Lexia. That'll really muck up the engine ECU mixture regulation and make it run rather rich and could be causing all the symptoms you see...

[Vuk1987]

I replaced temperature sensor 2 days ago, and a year before that. That's the reason I'm excluding it as a cause. I put a Vernet Calorstat brand. The reason it's showing -40 in some errors is probably because I drove it with the sensor unplugged. Now I suspect that it is either sensor harness, or something worse. I will also check fuel pressure.

[wheeler]

Have you unplugged the ecu connectors to check for water or coolant in the pins?
Its not unknown for the temp sensors to crack & allow coolant to travel up the wiring & into the ecu.

[Vuk1987]

Have you unplugged the ecu connectors to check for water or coolant in the pins?
Its not unknown for the temp sensors to crack & allow coolant to travel up the wiring & into the ecu.

I will definitely try that