Accidently put diesel gas in my mercedes, what do I do.

Year make and model, and are you saying you put diesel into a gas tank ?

check your car underneed.all

This is a bit pf a custom car type lash up and untill you can get some local advice here dont use the car as the excess fuel will wash oil from the cylinder walls causing piston /and ring damage ,You need someone local who can sort out and re-map the fuel injection system for you just for starters,Nice try and do admire greatly your determination in making something work but as iam in spain iam not a lot of help on this matter also owing to europeon vehicle law i wouldnt be allowed to do this for a rad vehicle as it detract from the certificate of homoglonation so a non standard vehicle just isnt allowed ,cannot even change the back lights for a fancy one let alone a engine

You must remove the gas tank and flush it out with clean water then with denatured alcohol and then let it dry. You will also need to replace the fuel filter and purge the fuel lines.

This is not unusual on a diesel. What happens is there is air in the system. If this vehicle has an electric fuel pump loosen line where fuel enters injection pump then turn ignition key to the on position and watch for fuel to appear and then quickly tighten line before turning off key. Then try to start. If does not have electric fuel pump will need a second person. One will loosen line and watch while other cranks vehicle until you get fuel and tighten line before the other person releases ignition switch unless vehicle starts first. If that doesn't do the job do this where line hooks onto each injector. Probably will not have to do this to all injectors but could run rough until all the air gets out of everything. I have farmed with diesel tractor for 25 years and dad I drove the gm vehicles with the 5.7. You normally don't start a diesel without bleeding the air out of the lines although some will self bleed most won't. Hope this does the trick.

Just keep going its probably got a load of muck in it from the bottom of the tank put some injector cleaner in fuel tank and it shouk put its self right

Car not starting or turning over indicates towards multiple possibilities. It can be issue with battery or weak battery. But if battery checks out ok, then it can be starter issue or faulty alternator or problem with low fuel pressure or no spark at spark plugs due to dirty spark plugs or faulty ignition coil or injectors getting cracked or dirty and needs to be cleaned.

To confirm the problem, the basic troubleshooting is required.

Click this link below and follow the troubleshooting:------

http://technoanswers.blogspot.in/2012/02/car-starting-issues.html

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This will help.

Thanks

I don't think going to AutoZone for codes is of much
value to anyone

Obviously your LS don't miss on 4 cyl or have 4 bad coils

You didn't need to replace any coils except the one that fails,
which is 1 or 2 a year on that car.

You most likely have one really bad coil that sets all kinds
of codes.

You can buy one new coil & walk it every couple days until
you get to the bad one or go to a repair shop with an oscilloscope
and the correct inductive coil adapter.

You need to use the correct OEM style plugs (NGK)
were the motorcraft mfg.

Check alternator output with a scope & make sure
the battery isn't more than 4 years old. Todays cars
are sensitive to voltage,current,resistance and grounds

Clean the MAF Sensor (crc maf cleaner)

At 100,000 miles replace front O2 Sensors

Are you sure you did not put diesel in by accident or E-85? The VW will run on regular gas(not recomended) but diesel or E-85 gas is Bad for it. The E-85 can clog up stuff. You will need to drain and flush the fuel system, a new pump might help and all filters as well. Sounds like you got E-85 or Diesel by mistake. If this is helpful, please leave feedback. Thanks, SP

You have to drain you fuel tank completely, and refill with diesel only.
Hopefully it didn't already cause too much damage to the glow plugs and engine in general.