W164 sounds very dieselly under accel

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beeza

New Member
Joined
Aug 24, 2014
Messages
10
Car
ML280CDI
My OM642 engine has been recently cured of the smoking problem during idle. It turned out to be the valve seals that had gone hard.

It was an engine out job and quite fiddly to do the seals without removing the heads, but worth it.

I now have a new fault. Although it doesn't make the vehicle undriveable, I would like to get a positive diagnosis. It is down on power and more noticeable down on low end torque. When I accelerate from around 1500 rpm, the engine labours and sounds very dieselly. Eventually the revs pick up and it gathers speed and once beyond 3000rpm it really flies.

So far components that have been replaced are:
Complete turbo assembly inc actuator (refurb)
Fuel filter OEM.
Air filters K&N
Air mass flow sensors X2
EGR valve
All 6 injectors (refurb)

I have checked for:
Fuel leaks on pressure and return lines. Incidentally fuel economy is very good.
Intercooler leaks. I did have a leaking O ring from turbo to the metal charge air pipe. It's reduced the whooshing noise, but no improvement on performance.
It does not have a DPF or Cat as it is for a foreign market.

I am leaning towards insufficient fuel pressure, although its not giving me any codes on my Chinese Xentry clone.

Is there a strainer in the fuel tank that if blocked could cause these symptoms?
Could the electric pump in the tank cause these symptoms?
How is fuel rail pressure regulated? Is there a user replaceable solenoid or valve that could be the culprit?
 
What did you do to keep the valves closed to get the springs off the valves?
 

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