Is your fuel gauge going crazy? Does you car show only ¾ full after you fill it completely? The problem could be your fuel level sender. Replacement is relatively easy, however it does require working around raw gasoline. In this article, I’ll go over the steps involved with changing out the sender.
The sender works by measuring the resistance of the electrical circuit depending on the location of the float. There is also a contact at the bottom of the unit that the sender closes to activate the low fuel warning light. Over time, corrosion can build up on the sender’s electrical components. This results in the gauge registering incorrectly.
Replacing the fuel level sender on the Mercedes-Benz W210 is an easy job provided you take the time to make it a safe job. The first step in replacement is to prep the car. Typically, you would want to drive the car until it is almost out of fuel. Alternatively, you can use a small hand pump to pump most of the gasoline out of the tank. The key here is to get as much fuel out of the tank as possible.
Another important thing to remember: always disconnect the battery when working near the tank. You don't want any accidental sparks from any electrical connections. Keep in mind that gasoline vapors are much more flammable then gasoline itself. An errant spark could cause an explosion. The bottom line is to think about safety at all times. Here are some things you should also consider:
Always have a fire extinguisher handy in case an emergency arises.
Gasoline is highly flammable. When working around fuel and fuel line connections, don't disconnect any wires or electrical connections that may cause electrical sparks.
Always remove the gas cap to relieve any pressure in the tank prior to working on the fuel system.
Do not use a work lamp when working near fuel or fuel tanks. If you need some light, use a cool fluorescent lamp and keep it far away from the pump.
Gasoline vapors are strong, harmful, and can cause you to become drowsy and not think straight. Always perform work in a well-ventilated area with plenty of fresh air blowing through.
Always disconnect the battery when working on the fuel system. Leave it disconnected for at least 30 minutes to allow any residual electrical charge in components to dissipate.
Keep plenty of paper towels on hand, and wear rubber gloves to prevent spilling gasoline on your hands
Be well grounded - don't do
anything that will create static electricity. Keep all cell phones and
pagers a safe distance away.
The fuel level sender is located in the fuel tank. The tank is accessed by opening the rear trunk. Remove the spare tire cover first. You’ll need to remove the rear inner trunk liner. This is held in place by four plastic rivets (green arrows) and two Phillips head screws (purple arrows).
The factory procedure for removing the sender calls for the use of a special pin wrench that fits into the two holes on the sender (green arrows). You can also use a large pair of channel locks to grab the outside of the sender and rotate it counter-clockwise. This will unlock the sender from the tank.
As you remove the sender, you’ll want to carefully remove both the upper part of the sender and also the float arm out from inside the fuel tank. At this point, you can see how the sender works. As the level of gasoline in the tank changes, the float moves up or down.
The float is connected to a rheostat that varies the amount of resistance that is sent to the fuel gauge. As a car ages, corrosion can build up in the rheostat, thus creating artificial resistance in the circuit. This increased electrical resistance can cause false readings or cause the gauge to not register at all. Sometimes you can carefully clean the rheostat with a bit of fine sandpaper and fix the problem (green arrow). A good way to check is to take a multimeter and check the resistance of the rheostat with the float all the way down and compare it as the float sweeps all the way up. The resistance should increase as you lift the float.
Take the new fuel level sender and place it in the hole in the fuel tank. Make sure that you have the correct orientation of the float. It should be facing down once you have installed the sender. You’ll want to keep the two locating holes for the wrench at a 12 o’clock and 6 o’clock position (green arrows) as you secure it into place. Once installed, lock the sender in place, re-connect the electrical harnesses going to the sender and re-install the trunk liner.
Comments: It worked; no diagnostic tool needed. I used a pencil eraser to clean the rheostatwhich seemed clean but actually was not. Removal tool was a wide mouth Vice-Grip.
July 28, 2014
Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
Comments: hi is it a must to hook up the star diagnostic tool if i do all the steps listed above for my new gauge to work?
July 7, 2014
Followup from the Pelican Staff: I don't believe so, the article does not mention the need for the tool. - Nick at Pelican Parts
Comments: My 1999 W210 E240 has the fuel guage indicating full tank when tank is actually empty, and indicating empty with the warning light on when tank is actually full.
Any clues and fixes?
March 4, 2014
Followup from the Pelican Staff: Sounds to me like a faulty sending unit or the wrong part installed. Has this part been replaced recently? It may be the wrong part number. - Nick at Pelican Parts
Comments: Pencil eraser much better to use than sand paper to clean contacts. Also 2 phillips and a long slotted screwdriver can be used to remove sending unit. Put the two phillips into the two holes and use the long slotted screwdriver to turn the two phillips.
March 3, 2014
Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
Comments: Jey, you will need to hook up the car to a Star diagnostic tool. There is a procedure for making all gauges go to full highest value on the gauge and hold it there for three seconds then drop back down.
March 2, 2014
Followup from the Pelican Staff: Thanks for the input on this one. We appreciate the help.
- Nick at Pelican Parts
Comments: Friend, need advice. My w210 e230 fuel meter cluster indicates fuel level at 1/4 but my petrol tank was empty. My car stopped by itself. There was no warning light also. I manage to re-fill petrol and my car manage to start back. Is the fuel gauge need to be replaced or the meter cluster is faulty. When I turn off the engine, the meter drops to zero.
June 12, 2013
Followup from the Pelican Staff: Sorry, I can't answer your questions.
This requires Local hands on diagnosis.
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