Fueling Problems

[SLeazy Rider]

I'm a new SL owner with very little knowledge of the inner workings of cars, so please bear with me. I have two fueling problems, which appear to my untrained eye to be related. First, when I am fueling the car the automatic shut-off feature on the pump keeps engaging unless I run it VERY slowly; it keeps acting like the tank is full, and shutting off the pump, unless I barely hold the trigger on the pump. This makes it take forever to fill the tank. Second, the tank is not getting completely full. Eventually, the pump's automatic shut-off feature completely engages and won't let me fill any more, even at a snail's pace. It would appear at that point that the tank is finally full. However, when I turn on the car, it shows slightly better than 3/4 of a tank. The first time I filled it up, it took approximately 16 gallons. The second time I filled it up, it barely took 15 gallons. I haven't looked in the owner's manual yet, but I suspect the car will hold a good bit more than that.

I have tried to figure out the problem by doing a keyword search on this site, but haven't found anything decisive yet. I've found a lot of threads dealing with issues with a "fuel sender". Is that the item that is causing my problem? If so, how do I correct it? How much should it cost to have it corrected by a good mechanic (realizing that I'm a total idiot when it comes to DIY repairs)? Thanks.

SLeazy Rider

[bwheitman]

I get that sometimes on my 96 SL320, I have to move the pump a little out of the hole to the tank. Sometimes you can move it out of the filler hole a little bit and try again. The problem is that the air pressure is setting it off. Moving the pump out a bit will allow the air to flow back out of the hole. Give this a try and it should work, just make sure you don't move it too far out that it falls out, just enough to allow air to move. Think of a bottle, if you put water in it, the air has to be displaced, if the air can't go anywhere the water can't go in. This is what causes the pump to shut off. There should be a small hole above your filler hole in that model, I am not sure, if not then I would recemmend checking your vapor recovery system off the fuel tank. If that is clogged or not working properly it will also cause this. It is important to maintain these systems because the fuel tanks have been known to collapse. It takes the vapors and burns them in the engine rather than releasing them into the air. Check the owners manual for capacity of your tank, try adjusting the pump and filling it completly up. Report back and let us know how that works!
Brian

[TX76513]

Rotate the entire fuel nozzle around so that the handle is "up" - that will probably help you out

[SLeazy Rider]

Thanks for the ideas guys. I'll try them out next time I fill up and will post an update, probably sometime the latter part of next week.

[aharley1]

"15 gallons...late next week"
Sure wish I could make 15 gal. last 2 weeks!!
Pulling the nozzle out 1/2 way should cure your problem & 15 gal is probably about right for a fill-up. My manual says capacity of 22.5 US Gal for my 1988 560SL, so if you're filling up below 1/2 of a tank, you'd be close.

[SLeazy Rider]

Well, the advice worked. Boy do I feel stupid. All I had to do was pull the nozzle about half way out of the fuel intake and . . . VOILA! . . . no more problems. Thanks guys. I'll hit you with a few more difficult problems (I think) later.