Greystoke

Hi,

On my 06 ML320 CDI W164 the Fuel Gauge Reads Full once the ignition is switched on.
If I add more fuel the mileage range on the display doesn't increase.

The gauge never drop down from full.
What should I check to find the problem.

Is there a guide to finding where the fuel float is and removal for testing.

Thanks

V12toHybrid

it happened to my w163 ml320 before too. it went from full to empty in the middle of nowhere. scared the heck of us. we filled it up and record the full mileage and just monitor it. it probably just got stuck temporary. after we fill it up, it went fine for awhile. my wife was freaking out (because she was the one driving it). before we could get an appointment to get it fixed, it went fine by itself. that was more than a yr ago. hopefully yours will be fine too.

Greystoke

It's been like this for a while now and never moves from full once the ignition is on. What I really need is a guide to getting to the fuel float.

AudiA4Turbo22

Bad Fuel Sending Unit.

It's essentially the electronic sensor that tells the car how much gas is in there.

Common problem.

Greystoke

Where can I find this

AudiA4Turbo22

Should be right next to or attached to the fuel pump assembly. I can't remember if the fuel pump is accessible from under the seat or not.

Greystoke

Does anyone have instructions to get at the fuel pump assembly.

AudiA4Turbo22

If you DIY you should invest in this:

http://www.mercedesmanuals.com/2006_...p270016406.htm

dgiturbo

Try Star Tekinfo.
Think it's about $18 bucks a day, and you can print out all you need or think you will need in the future.
Hope that helps.

Greystoke

Hi,

It won't allow me register as it is only available to US residents.

Thanks

u001elg

If you are hell bent to remove/diagnose the fuel sending unit yourself...

The fuel filter (gasoline models) is an integral part of the fuel sending unit and you need to replace the entire assembly.

Above and beyond standard parts and tools, you will need:
1) Two (2) fuel tank locking ring/O-ring kits with new hardware
2) Heat Gun and flat scraper
3) Body Seam Sealer (I use 3M Ultrapro Sealant p/n 051135-08300)
4) Fuel sending unit assembly
5) Fuel sending unit removal tool (Snap-On or equal)

Lower fuel level to below 1/4 tank or be prepared to remove fuel from tank.
Ensure ignition off, vehicle on flat surface and fire extinguisher readily available.

The fuel tank is located below the back seat.
Lift bottoms of rear seats to their full upright position.
Remove carpeting/ floor covering.
You will see two steel access plates. (one on each side)
Carefully heat the sealant and edges of the plate to soften sealant.
Gently pry the plates off and remove sealant material to ensure a clean surface for reassembly.
You should now see the fuel pump and fuel sender locking rings on top of the fuel tank.
Disconnect fuel lines and electrical connectors.
Using the removal tool, unscrew the locking rings and O-rings and discard.
If fuel level much above 1/4 tank, siphon or pump fuel to a container.
The fuel sending unit and fuel pump are connected via. an equalizing line in the tank.
Carefully lift up both fuel pump (on one side) and fuel sending unit (on other side)
Disconnect lines/wires holding the fuel sending unit in place and the equalizing line and remove sending unit.

Install in reverse order.

I hope this helps... obviously be careful with gasoline and the interior of your vehicle and no open flames/sparks with the fuel tank open.

The dealerships/independents typically charge about 3-4 hours labor. The first time you do this I would set aside the day just to get comfortable with the procedure. The next time you replace the fuel filter the job will go faster...

V12toHybrid

instead of printing them out, can you save the files instead?

Greystoke

Is this the same for the Diesel Model

dgiturbo

Diesel uses a different and much larger fuel tank. Didn't realize you were non US. See if this link helps? Look for the W164 DVD Manual and verify it has diesel info.

02ML320, I am sure you can save them somehow, but I don't remember how. The ones I have saved are in .pdf. I actually use Apple Mac's now, and can't even access the site anymore. They are PC based.

Greystoke

I got the fuel filter out and when I meter across the connector for the fuel level, I am getting a reading of .996 Kohms for empty and around 111ohms when moved near full.

Can anyone verify if these reading are correct.

AudiA4Turbo22

That sounds about right, the fact that the numbers are changing definitely seems like the system is working as it should.

The sensor most likely failed and is stuck at full.

Greystoke

Hi,

What sensor do you think has failed and stuck at full.

AudiA4Turbo22

How are you getting the full and empty readings?

Are you moving a float? or is it a level sensor?

Greystoke

I am manually moving the float and taking the readings from the cable connected to it

AudiA4Turbo22

Okay, so the float may have been stuck. It is the only way to get the incorrect fuel gauge reading. I would grease the float mechanism to where it is moving freely and reinstall it into the vehicle. It should work from there forward.

Greystoke

When I opened the fuel gauge sender side, that side of the tank was empty and the float was at the bottom. The fuel pump side is half full of fuel.
It looks like the fuel levelling moved all the fuel to the pump side as the gauge is reading full.

I have reconnected the fuel gauge sender side with the fuel pump connection left disconnected and the gauge goes straight to full.

I put a variable resistor on to where the fuel gauge sender side would connect and when it was at 1ohm the gauge showed full. As I adjusted the variable resistor up to 20Kohms the gauge read half full.

Is the fuel gauge sender side connect directly to the dash fuel gauge or does it go through something first.

AudiA4Turbo22

Possibly the fuel regulator, but it may be built into the fuel filter.

Do you have SDS?

Greystoke

No, I don't have Star Diagnostics and MB want €100/hour to run diagnostics on it. And they say it will take 1.5 hours.

AudiA4Turbo22

Well, go to the local forum to see if anyone has SDS in your area and can help you out. It will provide either a code or SDS will allow you to test the system to see if there is fault.

I doubt any wires have been severed.

AudiA4Turbo22

Oh and BTW after some more research I found out that their are 2 sensors in the tank for fuel levels, one that takes care of full to half and the other does half to empty. Change both sensors.