E63 AMG W212 engine chirp (not pulleys)

[Hamish90]

Hi all, have a somewhat perplexing problem; recently purchased E63 W212 and have a chirp / crickets type noise coming engine area. Had the check engine warning light come on for a "low pressure at the fuel rail" code - took this to a garage and they said it had likely come on due to booting the car with low fuel, cleared code, I refueled and it didn't come back on. However on long drive the day after the warning, I started to hear this chirp noise, which occurs at low revs and goes away when putting foot down. Car hasn't cut out and seems fine to drive, but the noise is concerning and quite loud, so don't want to damage engine, as something is clearly failing.

Been to a number of garages, they checked serpentine belt and pulleys which are all fine. No one is able to properly identify / diagnose, first garage suggested fuel pump, second indy merc garage thought it was a flap on the inlet manifold, but have had advice that these rarely go, and they wanted a lot of money to get at it, so took it to an AMG indy specialist who believe it is somewhere in the fuel system. Had both the HP fuel pumps replaced and also the low pressure replaced, yet the noise persists.

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Please see the video of the sound, as can be seen when the HP fuel pump is disconnected the noise goes away, which is why mechanic believes it is not the engine / inlet manifold, but something in the fuel system, but not the pumps, as these have all been replaced. Next theory is if it has had a remap in the past that could cause a fuel issue, so mechanic is going to analyse the fuel data vs standard spec.

Any ideas please? A bit at a loss so seeing if anyone has had anything similar on the forum. Disheartening problem having only had the car a couple of months but surely it should be resolvable! Many thanks

 

[E55BOF]

If it goes away when the HP fuel pump is disconnected, it does seem likely that it is in the fuel system. There must be some sort of overpressure relief valve to control the pressure in the system; could that be chattering when it operates, when actual fuel demand is lowest and therefore most is returned to the tank?

 

[Gbrowncls55]

A faulty fuel pressure sensor might lead to the above?

 

[optimusprime]

Noise is best found with a stethoscope . Sound is like some thing rubbing .First of all i would remove all the covers on top of engine if you have not yet done so .

 

[alexanderfoti]

Did the low fuel pressure event occur after changing the pumps? Its not impossible to kill the HP pump with fuel starvation.

 

[Hamish90]

Thanks very much for all of your replies. I will pass them onto mechanic currently investigating it. Re stethoscope that has been done, isn’t really clear where exactly it’s coming from but apparently sounds like it comes from somewhere around the inlet manifold which is why first garage thought that was the issue, however as said when fuel disconnected noise goes, which suggests not a prob with manifold.

The low pressure event occurred before the noise started. I have been using the car a little bit recently and the noise does seem to get quieter once it’s been driven for a while.

Any more ideas much very much welcome, cheers.