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Ask Michael Warfield Your Own Question

Michael Warfield
Michael Warfield, Factory Mercedes-Benz Technician
Category: Mercedes
Satisfied Customers: 2979
Experience:  Mercedes-Benz Master Certified technician
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How to drain fuel tank on 2012 ML350 BlueTech?

Resolved Question:

How to drain fuel tank on 2012 ML350 BlueTech?
Submitted: 2 years ago.
Category: Mercedes
Expert:  Michael Warfield replied 2 years ago.

Michael Warfield :

You must remove the low pressure hose off of the high pressure pump on the left front of the engine. You will see a rubber hose coming from the fuel filter hosegoing to the high pressure pump, just remove this rubber hose and run it into a container. You may want to purchase some extra long hose so you can set the container on the ground. Now you must jump the fuel pump relay with a jumper wire.

Michael Warfield :

I'll post instructions on how to do it in a few minutes. The relay is in the right rear panel in the cargo area. I just have to look up which fuse number it is.


 

Michael Warfield :

I mean relay number.


 

Customer:

Micheal, to see rubber hose coming from the fuel filter hosegoing, do I have to look from top or from under the engine?

Michael Warfield :

No right on top


 

Michael Warfield :

You took off the one piece engine cover right?


 

Michael Warfield :

You don't have to go under the car at all for this procedure


 

Customer:

Do you have any photos of the hose, by any chance?

Customer:

I assume, it's easy to disconnect the hose from high pressure pump and no need any clamps or whatever to connect it back?

Michael Warfield :

Well maybe just a few hose clamps


 

Michael Warfield :

I'll post a pic


 

Customer:

what's jumper wire?

Michael Warfield :

Just a wire use to connect 2 terminals together

Michael Warfield :

Did you fill your tank up with gasoline?


 

Customer:

No, I need to drain it for shipping

Michael Warfield :

ok


 

Michael Warfield :

Full Size Image


 

Michael Warfield :

You will notice this high pressure pump on the driver's side front of the engine


 

Michael Warfield :

Right where the yellow arrow is pointing, there is a rubber hose that is clamped there.


 

Michael Warfield :

Take this rubber hose off and follow it to the fuel filter about 10 inches away.


 

Michael Warfield :

Remove this end of the hose also. Take this hose to an autoparts store and buy like 6 feet worth of hose that same size.


 

Michael Warfield :

Connect the new 6ft rubber hose to the fuel filter and put the other end into a suitable container


 

Customer:

when I will jump wire the relay, the fuel will start to flow from the filter housing, right? Or I have to start engine too?

Michael Warfield :

No, just jump the relay. That will turn the pump on and pump it all out into the container


 

Michael Warfield :

The engine will not start anyways since you are disconnecting the fuel line to it.


 

Michael Warfield :

Post your vin # XXXXX I'll look up the relay location.


 

Customer:

OK. waiting for fuse number.

Michael Warfield :

fuse 57, there should be a small black relay right next to it

Michael Warfield :

To make sure it is the relay, pull the relay and try and start the car. If it doesn't start, then you have found the right one. The engine should just turn over but not start

Michael Warfield :

You should notice the relay has 5 pins on it


 

Michael Warfield :

You will need to jump pins 30 and 87 with a makeshift wire


 

Michael Warfield :

I mean make your own wire


 

Michael Warfield :

You actually could pop the cover off of the relay and get something to pinch the 2 conacts together if you don't want to make a jumper wire


 

Customer:

Is it all the same, including fuse number, for gasoline 2012 ML350? (I will have it in 2 weeks, and likely would have to drain it's fuel too).

Michael Warfield :

Yes, same for the gasoline engine too


 

Michael Warfield :

Except to drain that fuel system, you will need a different hose.


 

Michael Warfield :

To connect to the fuel rail under the hood.


 

Customer:

Michael, looks like I got the answer. I am planning to drain it on Monday. Can I hit accept after I do it?

Michael Warfield :

You will need this hose. http://www.tooltopia.com/mastercool-84722.aspx


 

Michael Warfield :

Yes, you can wait until then


 

Customer:

you mean this hose for gasoline ML350?

Michael Warfield :

The hose I just showed you screws into the fuel rail on the gasoline engine for all mercedes


 

Michael Warfield :

Yes


 

Michael Warfield :

There are no rubber hoses to disconnect on the gasoline engine but there is a nice test port on the fuel rail that that hose will screw onto


 

Customer:

OK.

Michael Warfield :

Use the kinked end of the hose to screw onto the fuel rail since that hose is only a one way flowing hose


 

Michael Warfield :

If you connect it to the other end, no fuel will flow


 

Customer:

got it. Is fuel rail located at the same place?

Michael Warfield :

Its actually on the passenger side, right on top. You will have to lift up the air cleaner a little bit to see it. There is a black plastic cap covering the test port.


 

Michael Warfield :

I'll post a picture.


 

Michael Warfield :

Actually, sorry the gasoline port should be right on top in the center with a black plastic cap


 

Michael Warfield :

I don't think I'll be able to locate a picture for that right now but it should be pretty obvious.


 

Customer:

OK

Customer:

does pins 30 and 87 has this numbers on them or how I have to figure out which 2 out of 5? thanks

Michael Warfield :

No the relay is marked 30,31, 87,87a


 

Michael Warfield :

So just use pins 30 which is means battery power in mercedes-benz terms. And 87 which means switched battery power.


 

Michael Warfield :

So you are really just jumping the normally constant battery power "circuit 30" to the fuel pump.


 

Michael Warfield :

Do not connect it to 87a


 

Michael Warfield :

Just 87

Customer:

understood

Michael Warfield :

So just talk to me Monday if you have any questions. I work at the dealer during normal business hours so I may not be able to respond immediately


 

Customer:

OK

Customer:

I will try and look at it tomorrow

Michael Warfield :

Ok, just let me know.

Michael Warfield :
Michael Warfield, Factory Mercedes-Benz Technician
Category: Mercedes
Satisfied Customers: 2979
Experience: Mercedes-Benz Master Certified technician
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