swecs

I have a C Class W202 1995 Gas / Petrol
The fuel has been contaminated, most likely by diesel.
There was about 3 gallons of good fuel in the tank when 5 gallons of bad fuel was added.
The car stopped after 50 yards.
So I now have 8 gallons in the tank I need to drain.

My question is, what is the easiest way to drain the fuel tank?
Also can anyone advise on how best to clean the fuel lines and injectors.

smirlex

I have a 97 c230 with the same problem (contaminated gas). The gauge shows about half a tank. I pulled off the larger rubber tube between the tank & the fuel pump.(passenger side, rear of tank). It drained about 2 gals in 5 min (be ready to catch it) but no more. I still don't know how gas gets from the left side of the tank to the right, after the level drops below the drive shaft height.Any ideas?

smirlex

I found another answer here: http://www.mbclub.co.uk/forums/engin...-question.html

smirlex

One more thing. There are supposed to be drain plugs in the tank sensors. One on each side, under a plastic cover. That's what I'm trying next. I'd hate to have to pull those sensors to drain the tank.

s2mangas2

the way we did it years ago was to insert some rubber hose pipe into the tank, then hold the other end below the lowest height of the tank, then suck on the hose very quickly and remove your lips/mouth and point the hose into a suitable bucket/container.

if it doesnt work first time try again, it's all gravity after all

smirlex

I tried that, (we call that an Alabama credit card down here) first thing. There is something in the filler neck that prevents this (a screen maybe). I tried a piece of butyl hose, since it was fairly stiff and only 3/8" OD.
No luck. It would not reach the fluid. I guess that's why there no lock on the fuel door. Thanks

jc1kz

No lock on the fuel door? Mine locks every time I lock the doors...(the trunk locks the gas door locks and the doors lock and the alarm sets...)

smirlex

Sorry, mine had been disabled, I never thought to look for it. Thanks.
I screwed out the aluminum plugs from the sensors on each side. There is a check valve behind it, you have to insert something in there to defeat it. Even then it drains very slowly, unless I've finally got all the gas out. If you remove the "O" ring from the plug & reinsert it, it might defeat the check valve. There is a very small groove on the face of the plug that looks as if it was there for that purpose. Would MB do a thing like that?

vinceC

M-B has a tool that fits onto the drain ports. Using the tool they suck the fuel from the tank. The best a layman can do is drain through the ports the best you can, then remove the sensors. There is quite a bit of fuel left in the tank when you remove the sensors so be prepared. The shape of the tank makes it necessary to remove both sensors. Also, after the sensors are out there is still fuel left in the bottom recesses of the tank. It can be mopped up with a sponge (a real PITA). Also, there are hose assemblies inside the tank that connect the sensors. They remain after removing the sensors, so none of the project is easy.

I didn't try, but it might be worth trying to disconnect the discharge side hose of the fuel pump and manually activate the pump to pump the tank down.

smirlex

Thanks. That makes sense, it would be a strange fitting to fit that plug air tight enough to pump the gas out.
Can you describe how to activate the pump so that it will run without cranking the engine?
Where is the pump relay & which contacts should be jumped? Or would it be easier to just wire 12v at the pump?

vinceC

I never tried the pump method and never looked for the relay. I believe the power to the pump comes down from the area under the forward end of the trunk mat (the area under the plastic floor cover). Perhaps it can be jumped directly from the battery to the leads inside the trunk.

You need to make sure the area is well ventilated, because, as you are probably aware, a spark in the right situation could cause something rather unpleasant.

smirlex

Thanks again, the wiring from the pump goes up thru the trunk floor before it breaks for a connector. I haven't tried to jump it yet.
I left those plugs out overnight with a piece of heavy wire in them to hold the check valve open & got another gal. out.
I'm with you on the gas/fire hazard. Don't ever crank the engine over with the injectors out & the gas line undone. Any slight backfire gets exciting. I won't say how I know this, but I'm really gun shy now.

smirlex

I stopped by my local hydraulic hose store with the plug from the tank sensor. & bought an adapter from 18mm x 1.5 thread to #8 JIC male. The 18mm end has the same 'o' ring seal as the plug.The id of the fitting is 3/8 inch. I inserted a piece of hose with 3/8 od (this was a 3/16 fuel line, but as long as it's a snug fit it should work). With this I siphoned 2 more gals of gas out of the right side that I was unable to get by taking the hose to the fuel pump off. I'm going to call that close enough & try to dilute whats left. Don't get this stuff in your mouth. Clear hose would help.
This was a Parker fitting.

Alternately you could drill out a 18mm x 1.5 bolt, seal the thread with Teflon tape & do the same thing.Or find the MB tool.
One more thing, I had to push the fuel line about 1/2 inch thru the adapter & notch the end of the hose to defeat the check valve & so that the check valve didn't seal on the end of the hose.
I didn't find any gas in the left side of the tank.??