After 6,500 miles the engine drives lumpy, sluggish acceleration and slow to start. Take to dealer who diagnose a faulty fuel pump. Over the weekend they change the story and now say gasoline was put into the engine and I have to pay for repair. It was refuelled 75 miles before going into the dealer with Diesel from a Mobil. I was under the impression if gasoline entered the tank it would not drive? What can or should I do?

 

Bring your receipt for the fuel with you while you demand a sample from the tank showing a mix of petrol and diesel. Inform them they're not to do anything to your car until such time as the analysis of the tank sample is complete, and if you can show that a) you just bought fuel recently and it was supposed to be the correct type, and b) the fuel they gave you wasn't mixed, you've got something.

Now, if it was mixed, should it have been mostly or completely petrol based on that last fuel-up? If so and it was, and your receipt actually does show you bought diesel, you take that to the Mobil station (or perhaps have your lawyer send a copy with the report on his own letterhead), and they pay for the repairs.

As for "will it drive," it's tough to say. But here is an article on the subject. (Rather technical.) It does say that the fuel pump would be affected, and I don't know how much you could even get away with using ULSD as its lubrication ability is even lower.

 

Many thanks

 

You don't say whether or not the "lumpy, sluggish acceleration and slow to start" occurred before or after the Mobil fill up (with whatever it was they put in). If after, then the sub par performance almost certainly is strongly related to the fill up. If before, and the fuel tests show a gasoline mix, then Mobil is off the hook (unless you can show the last several fill ups were there).
Diesel engines CAN run quite a ways on a gas-diesel mix. How long depends on how much diesel remained in the tank when gas was added and how much gas was put in. With only 10% gas in the diesel I would expect the engine to run quite a while but damage will certainly be taking place! With nearly 100% gas, you probably wouldn't be able to make it out of the service station before noticing serious problems.
Another potential issue: Was the Mobil fill-up self serve or did the attendant do it? The liability obviously changes depending on the answer.

 

The tank was just less than half full when it was re-filled from a Mobil Diesel pump in New Paltz, NY (the pump was on a separate island away from the gasoline pumps). It was then driven for 30 miles with no noticable issues at highway speeds - 65-75mph. It was re-started 2 hours later and the sluggish performance, slow start was then noticed.

 

Could be the blutec system and mass air flow sensor not detecting the proper fuel air mixture. My CEL is still on dealer doesn't know how to get it to go off. They replaced the temp sensor on the exhaust system but the CEL came back on a few days later. The really scary part is severe loss of acceleration when pulling out into traffic. Not sure if the two are related. My SA says it's a known issue MB just doesn't know how to fix it.

See my earlier post
https://mbworld.org/forums/gl-class-...-09-gl320.html

From benzworld
http://www.benzworld.org/forums/gl-c...mp-issues.html

 

Are you in the States? If so, do you mean to say "GL350"? I did not know MB made GL320s in 2010 for the U.S. market. I could be wrong. And FYI, diesel pump nozzles tend to be fatter than gasoline ones.

 

Oops, mea culpa, you said New Paltz. I live across from you on 84 in CT.

 

Yes, my typo - it is a 350. Car lives in Westchester, NY serviced in Greenwich, CT.

 

Given the 30 miles or so of 'normal' driving after fillup I'd guess that the problem is NOT gas in the tank. Partly plugged fuel filter and/or a malfunctioning fuel pump in the tank are increasingly better choices. Make the dealer PROVE there is a significant amount of gas in the tank (and try to make sure he didn't put it there [or in the sample analyzed] AFTER he 'decided' gas in the tank was the problem).
The following possibilities exist:
1) Mobil put gas in their underground tank that was supposed to have only ULSD. Unknown amount means an unknown percentage of gas/diesel. If this happened you are CERTAINLY not the only 'driver of a diesel' with a problem. The people who run the station would certainly have heard about it by now. Check with them.
2) Dirt/crud was stirred up in the underground tank and was pumped into your rig. Crud - not gas will be in your tank.
3) Fuel was normal and the fuel pump is messing up. Not an unusual problem in the 350 Blutec rigs. Solution is obvious
4) Some kind of an issue with the sensors and the computer causing a hard start, lack of power and sluggish performance. The possibilities here are nearly endless.