C63 fueling problems

[NiC63]

Hi guys looking for some advice here on what else to replace change as main dealers here in Cyprus cannot find anything wrong with the car and its been in 3 times in a month and a bill of 1,5k +.

2012 C63 AMG, M156, 62k on the clock. Always run on 100oct Fuel. Has stage 1 remap which has been on the car for the past 2 years. Only mod on the car is full catless.

This occured around a month ago but now became more frequent. After about 40m-1h drive when i accelerate hard i get the following fault codes and the car seems like it is out of fuel. If i drive at low speeds i can drive it all day with no problem.
There is hesitation, sometimes no acceleration it is un drive able. Clear the codes let it sit for 10 mins drives ok until you accelerate hard again. The code are stored and not current as i have had the car checked at a local specialist also. Last thing i am consider in changing is fuel pumps / fuel filter clogged ??

These are the fault codes i am getting-

-The Fuel Pressure sensor has a malfunction
-The Fuel Pressure im the system is too low

No engine light comes up, just loss of power like i have run out of fuel.
I have replaced the following-

Throttle body gaskets
IM Gaskets
All new bolts
Fuel pressure sensor
PCV Valve
Rocker cover gaskets
8 X Injectors cleaned and tested

If anyone can shed some light my way will be much apprceciated as i have lost faith in main dealer.

 

[ToeKnee]

Maybe fuel filter is blocked or clogged? When was the last time it was changed?

 

[NiC63]

I

Maybe fuel filter is blocked or clogged? When was the last time it was changed?

have no record of it every been changed. The filter sits inside the tank? Do we have a part number i can order to have that replaced also

 

[ToeKnee]

Sorry, no idea of the part number. On my SL, and a lot of other Mercedes, the fuel filter isn't inside the tank and is accessible, although I don't know the C63 well enough to say its the same.

 

[st13phil]

Blocked fuel tank breather? Next time it does it, undo the fuel filler cap. If you hear a whoosh as air rushes in, you’ve found the culprit.

 

[NiC63]

Blocked fuel tank breather? Next time it does it, undo the fuel filler cap. If you hear a whoosh as air rushes in, you’ve found the culprit.

Saying this now I think I heard that whoosh sound last time refuel. May I ask where the fuel tank breather is located

 

[st13phil]

May I ask where the fuel tank breather is located

Sorry, I can’t help with that but hopefully someone else will know.

 

[Jobsworth]

Does sound like a clogged filter or weak pump. I’d be connecting a fuel pressure gauge to the rail and watching the pressure when the fault occurs. I’ll bet the pressure drops off

 

[Alex]

As suggested above, hook a fuel pressure gauge to the rail, find an empty stretch of the road (or a dyno room) and monitor the pressure under different driving conditions.

The fuel pump in these is a PWM type - meaning it runs at half tilt under low load and ramps up when load in the engine increases. It is possible that the pump is either tired or not getting the signal (less likely). Since you've checked the injectors, I'd rule them out. Especially since those injectors are designed to flow more fuel than the engine can take.

Filter is less of a suspect in my books, simply because even "life" filters that are buried deep inside the tank's sealed cannisters of E55s (with their "dumb" always on twin pumps) do last forever and don't crumble even though they are filthy as hell when you get them out.

 

[NiC63]

Would you recommend changing both the fuel pumps. As I am aware we have two under the rear seats. Is one for high pressure? Is there a way to test them before I order a new pair?

 

[Alex]

Would you recommend changing both the fuel pumps. As I am aware we have two under the rear seats. Is one for high pressure? Is there a way to test them before I order a new pair?

You can certainly test them but unless you do it yourself or have a friendly automotive electrician, it will probably cost the same to just get a new pump assemby from Mercedes. This will be a single unit with a pair of pumps in it.

Not suggesting you to go and splash on a new fuel system as it's certainly not cheap but just giving you a comparison. Me, I'd start with diagnosing the fuel pressure drop, then see if the pumps can be swapped out for some aftermarket units. But if you don't have the confidence or skill to take on a project like this, it's almost always better to just get a replacement part from the dealer and have them install it.

 

[NiC63]

You can certainly test them but unless you do it yourself or have a friendly automotive electrician, it will probably cost the same to just get a new pump assemby from Mercedes. This will be a single unit with a pair of pumps in it.

Not suggesting you to go and splash on a new fuel system as it's certainly not cheap but just giving you a comparison. Me, I'd start with diagnosing the fuel pressure drop, then see if the pumps can be swapped out for some aftermarket units. But if you don't have the confidence or skill to take on a project like this, it's almost always better to just get a replacement part from the dealer and have them install it.

A friends friend is kind enough to let me visit his workshop and do some fuel pressure test. Where should my pressure be. 55-58psi? Shall we have the car rolling to get correct figures ? Shall we check figues on idle?

If it is the pump will i require the RIGHT side pump or the LEFT side pump. Left one been the drivers side is the jet pump is that the one that carries the fuel filter.

 

[NiC63]

We couldnt get the fuel pressure as the connections the mechanic had were to small, but another code came up which is as follows

U0100-64 The Control Unit 'combustion engine' has a malfunction. There is no impulsive signal 'Stored'

What the hell is this now

 

[Alex]

A friends friend is kind enough to let me visit his workshop and do some fuel pressure test. Where should my pressure be. 55-58psi? Shall we have the car rolling to get correct figures ? Shall we check figues on idle?

If it is the pump will i require the RIGHT side pump or the LEFT side pump. Left one been the drivers side is the jet pump is that the one that carries the fuel filter.

I don’t have access to MB tech info right now but the pressure shouldn’t be over 5 bars. You want to check the pressure when the car is going as this is where you experience the drop. The pumps are only in one side of the tank, the other side is siphoned. Fuel filter would be where the jet is, correct.