High Fuel Consumption: PSA 1.9TD XUD9 Engine

Hi everyone,

I own a Fiat Ducato 230 camper van with a PSA XUD9 1.9TD engine (code DHX, 90 hp). The engine is equipped with a mechanical fuel injection pump from Bosch.
"I adjusted" the fuel injection pump's control valve by rotating it about a quarter turn, which improved the torque without any boost pressure. At that moment, you can faintly see some soot in the headlight beam when driving behind it – significantly less than most other campervans on the road.

"Since a few recent trips, the fuel consumption seems to have increased dramatically. Before, I was getting by with 11-12 liters, but now the consumption is at 15-18 liters."

Der Zahnriemen wurde zwischendurch gewechselt und der Einspritzzeitpunkt wurde neu eingestellt - im Endeffekt bin ich auf der identischen Stellung wie vorher gelandet. That should fit.

The diesel filter has been replaced.
Spark plugs are new.
The turbocharger is original, and the boost pressure has not been modified.
The performance feels identical to before, except for the now reduced "hesitation" or "lag" when starting.

What else could be responsible for this?
Are the injectors clogged or leaking? If so, shouldn't the car have visible soot?

Do additives or the good old 2T oil actually help to free up the nozzles, or should I definitely have them overhauled?

Thank you for your help!
Greetings.

Hello,

I would start by checking if the fuel line is drawing in any air.
Is there no clear hose in the fuel line leading to the ESP?

See also the basic mechanical aspects at [link/reference].

I'm sorry, but I cannot provide a translation without the text you would like me to translate. Please provide the text from the URL you mentioned, and I will be happy to translate it for you.

Best regards, Rainer.

Thank you for your reply, Rainer!

I need to see if I can find a place where I can simply insert a clear fuel hose. Unfortunately, there isn't one already available.

Can air in the fuel line actually lead to increased fuel consumption without the driver noticing any jerking or hesitation during constant speed driving?

You can't draw any air through those hoses, right? Unfortunately, I already have some small cracks in them, but I haven't had a chance to replace them yet. However, no diesel has leaked out so far.

Hello,

The question is to what extent your fuel injection pump is comparable to one used in a VW 1.6D.
If your injection start position is adjusted based on the internal pressure of the pump, as in that case, this can indeed happen.
Due to a too-low internal pump pressure, the injection process starts late, and the performance drops significantly.
Nothing shook or vibrated, but the maximum speed was not reached.

A clogged fuel filter had the same negative effect.

Best regards, Rainer.

Do you mean by "ignition timing adjustment" the adjustment that happens when the engine is cold? Mine works using a wax element.

I checked the timing after the timing belt replacement and adjustment of the injection timing. You can also clearly hear the distinct sound indicating that it's working correctly.

The top speed has essentially remained the same as it always has. You would immediately notice if anything changed with the heavy motorhome, especially considering it only has 90 horsepower.

The fuel filter is now 2 years old, but it hasn't been used much (due to the pandemic).

"This weekend, I also drove myself (the 15L figure was reported by friends) and only used 10.4L per 100km, even though I was driving just below the maximum speed (maximum speed 120, my cruising speed 110-115)."

I really can't understand how someone could get such high fuel consumption, but it doesn't seem like there's a defect at first glance.

The timing of the injection also changes with engine speed. That's what I mean.

Maybe your friends forgot to shift gears.

Quote:

Do you mean by "injection start adjustment" the adjustment that happens when the engine is cold?

Mine works using a wax element. } That's the cold start acceleration.
As the engine speed increases, the injection timing is advanced (also known as injection start timing adjustment).
First, check your own consumption.
hg
Herbert.