jmurrdog

I have a 2010 E350 with a cracked fuel tank access closing cover (right). I filled the tank and then pulled the rear seat to verify the problem. Sure enough, small but steady leak, and associated fuel smell outside the vehicle. Can someone tell me how low the fuel level needs to be so I don’t overflow the tank when the cracked cover comes out?

kajtek1

You should be calculating the fill from your odometer if you don't want the top spill.
Some of those tanks did have recall in US, so if you are in this country, call your friendly SA and check.

konigstiger

Tank should be not more than 3/4 full.

jmurrdog

Calculating from full tank using the odometer doesn’t help me if I don’t know how much volume of fuel is above the level of the opening.

jmurrdog

Thank you! I was hoping you would respond. I know the maximum quantity is listed in the maintenance pages, but I don’t have access.

My W212

I always fill it full as needed to drive sixty miles a day. Any drawback for full filled?
On the other hand, I keep gas level over 1/4 as I learn from a friend that the fuel in the tank is needed for cooling down the fuel pump. Any comment?

jmurrdog

I replaced the cracked access cover yesterday. Konigstiger was correct….the fuel level needs to be 3/4 tank or less. My tank was between 7/8-3/4 full and overflowed slightly when I removed the cracked access cover. No leaks after I filled the tank with the new cover and other parts. I actually replaced 3 parts…..MB-2044700438, MB-2114710110, and MB-2114710179. Total cost $76 plus tax and shipping. My old cover had a very fine two inch crack that allowed fuel to slowly seep through the crack.There was no fuel smell inside the car, only outside. There is a seal on the metal plate that covers the hole in the bottom of the chassis under the rear seat. That keeps any fumes from entering the vehicle. 2010 E350 PZEV. Hopefully, this will help others, as the issue appears to be widespread. Many vehicles affected are not part of the various recalls…such as mine. For me, it was much easier to fix it myself than to waste time with incompetent SAs at the dealer.

Couch67

Nice work! Thanks for sharing the fix.

konigstiger

3/4 comment was regarding repair. No harm in keeping tank full. FWIW I never let any of my vehicles fall below half.

kajtek1

In my Ford T, I have to observe fuel level when driving on grades.
The fuel is gravity-feed and tank under the seat is just few inches higher than carburetor. With low fuel in tank on grade, the carburetor can be higher, but going on reverse solves the issue.
I take it OP never check for tank recall?
Gasoline engines don't need fuel flow for cooling, but with complicated tank shapes in modern vehicles, they do have return fuel used for Venturi pump to suck fuel from low point.
In case you run the tank dry, you usually need to add more than 5 gallons of fuel to prime main fuel pump, who is in higher point, or on other side of the saddle.
Diesels do have return fuel per engine design, but I run the tank down to 2 gallons even in 120F weather.
I hate spending time at fuel pumps and with our low driving E250 Bluetec needs refueling every 2-3 months.

CaliBenzDriver

I hope MB is proud of this dual tank saddle design with 3 to 5 fuel pumps in total.

This requires a twin fuel gauge set-up to measure each saddle quantity and some busy computation to figure the available gas quantity in US Gallons or Liters...

Our 2x gauges run off a 5V reference line and are both wired to the R-SAM network.

At that rate I wonder if they take in consideration the pitch sensor to evaluate or invalidate gas level downhill ?
😎

kajtek1

I am actually amazed with genuinely build saddle tanks. Sure they can make repairs nightmare, but for years I drove W210 sedans, who had tank behind rear seat.
Not only trunk was much smaller, but no pass thru, not even ski latch so taking the skis, I had them lay down on center console.
Fitting 20 gallons tank under rear seat sure took some engineering.