My 1999 E320 Benz suddenly will not permit me to fill it rapidly


#1

My Benz has 65K miles, on full it holds, I believe 18 gal. The last two times I have attempted to fill it (I never let the tank go below 1/2 before filling it to full so as to take advantage of low prices)I have had to “nurse it” to take last 4 gal or so. The vapor return to the tank will shut off the hose nozzle and only permit me to put in no more than 2 to 3 tenths at a trigger pull. Agravating to say the least and makes the station magr. annoyed as well. Any ideas as to the cause?


#2

On all modern cars there is a small hose that should run right next to the main filler tube. It’s there to allow air to get out of the fuel tank that is being displaced by gas as you fill up. The gas pumps that have the plastic bellows on the nozzle are designed to capture that air to not let it into the atmosphere…it’s a pollutant since it has a fairly high amount of gas vapor in it. My guess is that the vapor hose on your car got kinked or plugged. If you think it’s plugged, you could try taking some flexible wire and shoving it down that tube…look for a small hole right around where you stick the fuel nozzle to fill up. If it’s kinked, then the small wire isn’t going to help.

The downside to running a wire down there is that whatever gunk is blocking it will end up back in your fuel tank, and could end up partially clogging your in-tank fuel filter. But even if it did, you probably wouldn’t ever know because the in-tank filters usually have a fairly sizeable screen and a small piece of gunk wouldn’t restrict flow much at all.

That’s my guess anyway.


#3

That sounds certainly reasonable, as a matter of fact, I thought of this also but discarded it because I couldn’t see it possibly becoming clogged. Kinked or twisted? I’ll have to think about that some, even pinched seems remote as there probably isn’t enought length to permit that action. Anything possibilities forward of the tank?


#4

Have you been in the habit of topping off the tank? If so, that could be the problem. You can damage parts of the vapor recovery system and you may need some repair. It is also possible that any of several hoses may be kinked or loose.


#5

Mercedes requires that 91 octane be used because of the 10:1 compression ratio. Since I live in Denver (5500 feet) I have calculated that I can use 88 octane and be within factory eng. specs at this altitude. So, when the tank is empty I will fill it with 91 and let it go down to half then fill it with 85 then begin the sequence all over again but never letting the ratio go below 88 octane.


#6

I see that you are in denver, if you really want the answer go talk to Star Tech (Santa Fe Drive & I-25). The owner, Sandor, knows more about these cars than anyone else I know. He will also give you good advice on the octane question:

http://startechmercedes.com/


#7

Craig58,
Thank you, I will contact Mr. sandor


#8

Actually, Sandor is his first name, you won’t be disappointed. I might see you there, he’s currently replacing the engine in my '82 300D. If you see a yellow 300D with no engine, it’s mine. Tell him that Craig referred you.


#9

My Benzes have all been older than yours, but I may know what your problem is. In the filler neck there is a plate with a hole in it that the nozzle fits through. Since you have stuck the nozzle into this hole many many times over the course of nine years and filling at 1/2 a tank, you may have gradually pushed the plate farther and farther into the filler neck. For some unknown reason, that effects the way the sensor works. It continually shuts off the fuel supply. If you find the plate has receeded into the neck, bend a small hook into a piece of stout wire and pull back up to an acceptable level.