citroen C5 X7 2.0 hdi p0094, p0087, p0183

[farlimb]

Hey everyone!

I’ve been chasing a fuel-related issue on my C5 X7 2.0 HDi for the last few months, and I’m hoping someone here might have some ideas.

I keep getting the following fault codes on and off:

P0094 (small fuel leak)

P0087 (fuel pressure too low)

P0183 (fuel temp sensor high input)


Sometimes it’s just P0094, sometimes P0094 + P0183, and on rare occasions P0181 pops up too (only happened twice though).

My family member has the same C5 X7 with the same engine, and his runs perfectly. So we’ve been swapping parts from his car to mine to try and narrow things down.

So far I’ve replaced:

Fuel filter housing

Fuel lines to/from the HP pump

Injector return line


After changing the lines to and from the HP pump, it actually seemed to improve a bit — but the issue is still there.


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Symptoms

Before changing those lines, the car would go into limp mode every time I accelerated harder than half throttle going uphill.
It was super consistent — usually happened around 2,000 RPM in 5th or 6th gear.
Only once did it happen in 2nd gear, full throttle uphill.

It seems to be related to RPM and gear load, because it’ll also go into limp mode when overtaking under 3,000 RPM and in 5th or 6th gear, even on flat roads.

After replacing the HP pump lines (just today), it’s less frequent, but still triggers the same codes if I test it a few times going uphill.


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Starting Issue (Air in Fuel Lines?)

I think there might be air getting into the system, because if I park the car facing uphill — even on a small incline — it won’t start unless I prime the fuel a few times.
If it’s a steep hill, it won’t start at all, even after priming.

I’ll test again soon to see if that’s still the case now that the HP pump lines have been changed.


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Looking for Ideas

Any suggestions on what else I could check or replace to finally sort this out?
Maybe something I’ve missed in the fuel system?

VIN: VF7**************[VIN obfuscated, can be read by forum staff]

[mickthemaverick]

As you are getting low pressure faults and the problem occurs when you increase demand I wonder if you have a leak in the tank to front fuel line which allows you to suck air in when you up the demand. Worth checking the fuel line from the tank and the connections at the tank I would think.

[wurlycorner]

Have you monitored the fuel pressures to see what they actually reading and running at?
Also, not familiar with the set up on that car but is it a returnless system or does it have a return to tank?

[farlimb]

Have you monitored the fuel pressures to see what they actually reading and running at?
Also, not familiar with the set up on that car but is it a returnless system or does it have a return to tank?

I did monitor the fuel pressures but only with a cheap OBD2 and that didn't help much since I couldn't tell if the pressure drop was coming from the limp mode or the actual fuel pressure drop. Regarding your other question, yes it does have return to tank.

[farlimb]

As you are getting low pressure faults and the problem occurs when you increase demand I wonder if you have a leak in the tank to front fuel line which allows you to suck air in when you up the demand. Worth checking the fuel line from the tank and the connections at the tank I would think.

Thanks, I'll check up on that. By the way the car has 275k kms on the odometer so I guess any line could be faulty at this time. I also forgot to mention that I had to to put my injectors for reconditioning like 5k kms back since they were not good anymore but from what I know after that many kilometers it's basically maintenance.

I am thinking if there could some kind of clog in the system before the fuel filter? And if so wouldn't that be a problem for high rpms also ?

[wurlycorner]

If it’s a system with a tank return, then to me, the symptoms of the three codes suggest too much fuel being returned to the tank, due to a problem with the fuel pressure regulator perhaps?
It would obviously explain the first two but it also explains the last one (excess fuel temp is created by fuel being cycled from and back to the tank continuously - it gets heated up doing the circuit over and over).

Does it come up with over temp very quickly, or after a while?

[farlimb]

Update:
I have changed the gasket around the fuel tank for a new one with a new plastic ring around it, no change. Then i changed my fuel pressure regulator for a 9109-936A delphi genuine one which from delphi site says is superseeding my original 9109-937. After changing the fuel pressure regulator i get different errors - P0087 and P0088 so fuel rail pressure too low and fuel pressure too high. The car takes longer to start now. I managed to record graph of my relatives RHF c5 x7 and mine fuel rail pressure. His is nice and smooth at idle around the target of 250 +- 5. Mine is more erratic, jumping up and down from 250 to 200. Before the change of fuel pressure regulator it was a bit better, it jumped up and down but maybe to 215 not 200 like with the new one.

Any ideas what to do next?

[farlimb]

Last update RESOLVED:
After some diagnosing i have found out that my injectors are returning way too much diesel. About 5 mil. per min. per injector (way too much!). Bought brand new injectors and now the car runs fine, even with the new 9109-936A fuel regulator. For anyone wondering, yes 9109-936A is compatible on RHF engine. I am putting this information out since i couldn't find it anywhere.

[aerodynamica]

Great result, must have been really frustrating all this time.

[wurlycorner]

Excellent news, well done sorting it.
Pleasingly it does align with the initial diagnosis suggested, too (though for a different component being at fault)!