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My ML has recently developed the fuel gauge problem. I've searched here and read everything I could find, but nothing seems to make much sense in my situation. I developed a fuel gauge problem several years ago that resulted in the sending unit/pump being replaced. Since that repair it has worked fine. Suddenly it has started acting up again. When I fill up it does not register the fillup and runs the fuel level down to the gauge peg. Sometimes, out of the blue, it will work. Fill it up and it works until the next fillup, when it breaks. When it is full, but registering empty, accelerating and decelerating will cause the warning light to go on and off. Sometimes it seems going up or down hill will do the same thing. When it is not working, disconnecting the battery and reconnecting will fix it until the next fillup. I bought the Service DVD and it points at a Instrument Cluster software version problem. But my car worked for a year or more before developing the problem. I don't see how that can be a software problem. I don't see how disconnecting and reconnecting the battery would fix a problem with the sending unit. I've got potential issues in the AAM with my remote and central locking. IS the AAM involved in the fuel gausge operation too? Any suggestions appreciated.

Thanks,

Al
 

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As for the workarounds, you don't need to disconnect the battery for resetting the fuel gauge reading system.

There are two workarounds if you don't want to continue changing fuel pumps which come together with the senders.

1.- There is a fuse that you can inline with a switch to it, so that whenever you fill up your tank you just flip the switch and it will reset. The fuse is in the passenger compartment fuse box. You need to search on the old posts for the location details.

2.- The other is a connector in the driver's side rear wheel well, where if you diconnect the harness with the ignition off, and you wait a couple of seconds, then the fuel gauge mechanism will be reset.

Number one is more practical in my view.. On my former 2001 ML 320, I changed 3 fuel pumps and all develop sooner or later the gas gauge reading problem.

Even my brand new 2005 Ml 500 had the problem very early in life, around the first 2000 to 4000 miles. They fixed this one, though, by disabling how the gas left/averaging is calculated in the program. The side effect of this is that the gas reading is not uniform or linear as you may expect. This is more pronounced only when the tank is full. In my experience, when the tank is in the last quarter, it behaves much more uniformly.

AC
 

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Thanks for the post about fuse #5

MY 2001 ML320 exhibited the fuel gauge problem today. I filled fuel this morning on my way to work. Soon thereafter, the fuel gauge showed that it was empty despite a complete fillup. I drove to my office, searched BenzWorld and discovered fuse 5 technique. Turned key to position 2, pulled out fuse 5 with nose pliers in the fusebox located near front passenger, waited 20 seconds, put fuse back, turned key to off position, waited a few seconds and turned engine on and voila.. fuel gauge functions again as normal!! Thanks Benzworld!!!



As for the workarounds, you don't need to disconnect the battery for resetting the fuel gauge reading system.

There are two workarounds if you don't want to continue changing fuel pumps which come together with the senders.

1.- There is a fuse that you can inline with a switch to it, so that whenever you fill up your tank you just flip the switch and it will reset. The fuse is in the passenger compartment fuse box. You need to search on the old posts for the location details.

2.- The other is a connector in the driver's side rear wheel well, where if you diconnect the harness with the ignition off, and you wait a couple of seconds, then the fuel gauge mechanism will be reset.

Number one is more practical in my view.. On my former 2001 ML 320, I changed 3 fuel pumps and all develop sooner or later the gas gauge reading problem.

Even my brand new 2005 Ml 500 had the problem very early in life, around the first 2000 to 4000 miles. They fixed this one, though, by disabling how the gas left/averaging is calculated in the program. The side effect of this is that the gas reading is not uniform or linear as you may expect. This is more pronounced only when the tank is full. In my experience, when the tank is in the last quarter, it behaves much more uniformly.

AC
 

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As for the workarounds, you don't need to disconnect the battery for resetting the fuel gauge reading system.

There are two workarounds if you don't want to continue changing fuel pumps which come together with the senders.

1.- There is a fuse that you can inline with a switch to it, so that whenever you fill up your tank you just flip the switch and it will reset. The fuse is in the passenger compartment fuse box. You need to search on the old posts for the location details.

2.- The other is a connector in the driver's side rear wheel well, where if you diconnect the harness with the ignition off, and you wait a couple of seconds, then the fuel gauge mechanism will be reset.
Do these workarounds need to be performed after every fill up? In other words, if I reset the fuse after fill-up, will I need to do this again on the next fill-up? Or will the reset last for some number of fill-ups before requiring another reset?
 

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The gas reading problem is caused by different issues depending on the year model/etc of your ML.

In the case of my former 2001 ML 320, the problem started to happen from time to time only, and then, after it became more frequent, I had to reset it every time I filled the gas tank. For whatever reasons (part/labor profits or stupidity reasons),

Mercedes never fixed this basic problem during the lifetime of the W163 model, I wonder if Mercedes ever came up with a new fuel pump revision part, which does not have this shameful design/quality/material problem..

AC

Do these workarounds need to be performed after every fill up? In other words, if I reset the fuse after fill-up, will I need to do this again on the next fill-up? Or will the reset last for some number of fill-ups before requiring another reset?
 

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Mercedes like it even today, still selling fuel pump assembly for big $ instead of just the fuel sending unit by itself, FYI part No. A163 470 01 94 Some of them replaced under warranty, but very few compare to number of 163 MLs manufactured.
Mine is just not showing full on fillup, usually 3/4 or 7/8 max., in 3 years, I got used to it.
The sending unit potentiometer (variable resistor) wiper is exposed to fuel and acidity of the fuel will make coating or oxydation on the resistor surface in 1998-2001 MY.
Since 2001 I believe Mercedes installed resistance calibration circuit board to help the ECM to count fuel volume for trip computer.
I have a buletin for this printed out but I can't find it at this moment, I just remember that I had previously trouble to upload it into post so I scanned it and e-mailed it out to one of the forum members. I will try to find it and upload it.
Bernard
 

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I think it was also around that time the fuel filter design was changed and that required
a modified pump design.

I did the filter update and put in a new OEM pump with updated lines. It lasted about 75k miles
and the sender did break. I could actually see where 2 tiny little contacts had broken off
sender at the swivel point where the contacts for the sender are located. Now on pump number
three now for about a year and hopefully it will hold up for awhile.
 

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I never had one in my hands but I see the design with contacts exposed to fuel on picture (mine is still original with small filter at 168K miles). I have new upgrade filter and lines ready but truck is running fine and right now I have no spare time to play with it.
Bernard
 

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FYI, I have found the bulletin:
DTB May 13, 2002 order # T-B-54.30/64 group 54
Subject: model 163.154/174/175 year 2001 and 2002
Fuel gauge accuracy
If you encounter instances in the above model vehicles where the fuel gauge reading is inaccurate, please perform the following procedure prior to replacing any components.
1. Remove fuse 5 in the RSE2 fuse holder.
2. Reinstall fuse 5 into the RSE2 fuse holder.
3. Instruct the customers not to fill the fuel tank untill they have reached the 1/2 tank level on the fuel gauge.
The fuel gauge reading for MY01 and MY02 vehicles have a virtual calculation performed on the first 19 liters (MY02) or 7 liters (MY01) of fuel. When the vehicle is filled prior to depleting the gas tank to these levels, an offset is calculated and stored in the instrument cluster memory. This is the cumulative affect and can result in the vehicle showing an empty tank even when actually full of fuel. The above procedure will remove any offset stored in the instrument cluster and return the fuel gauge to the correct accuracy.
This may help you out and sorry for my late respond.
 

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That should work if the sender is not defective.

Based on the age of the vehicle if it is the original pump/sender unit it is probably a failure
and not a calibration issue.
 

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Mine used to do this and I had to perform the removal of fuse #5, as stated in the above bulletin, several times over a one year period.

It has mysteriously and thankfully been fine for the past year or so now.:)

I hope I haven't jinxed myself Mike.:eek:
 

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My gauge showed full at the last fill up but I doubt it will stay that way from now on.
Did anyone ever try to clean those contacts on sending unit for better accuracy of the gauge? I heard some of them corrode to the point of wiper end breaking off the float.
Is it possible for all of them to be jinxed?
Bernard
 

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Same problem???

Hi to all.
My ML98 has a problem like this but don`t know if it's the same yours.
My fuel gauge shows full thank but it is really empty. How do i fix that?
Thaks
 

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X18/3 connector inboard of left rear wheel has pin A (orange wire) and pin B (gray wire) comming from the level sending unit. At empty tank they should show 200 ohms, at full tank they should have 0.5 ohms of resistance. Disconnect this plug and turn the key on to see if the gauge needle will move (it should stay down at empty). Remove the key, check the resistance, your float may be stuck in upper position or these two wires are somehow shorted out.
Try to kick the fuel tank from below, this may break loose the stuck float lever.
Bernard
 

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Thanks

X18/3 connector inboard of left rear wheel has pin A (orange wire) and pin B (gray wire) comming from the level sending unit. At empty tank they should show 200 ohms, at full tank they should have 0.5 ohms of resistance. Disconnect this plug and turn the key on to see if the gauge needle will move (it should stay down at empty). Remove the key, check the resistance, your float may be stuck in upper position or these two wires are somehow shorted out.
Try to kick the fuel tank from below, this may break loose the stuck float lever.
Bernard
Thanks for your help, i will try this solutions soon, and wil tell you the results.
 

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One other trick that may avoid the need to continue reseting the gauge by pulling #5 fuse is to leave the ignition switch in position #2 during refueling. This appears to continue monitoring the fuel level and the gauge moves back to full as the gas is being added. This eliminates the need to hold your breath everytime you turn the key hoping your gauge will respond!
 

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I have a 2002, and the answer is "both". The fuse 5 or wheel well connector trick works sometimes, but lately the behavior is more like an electrical intermittent--at some points in the range there's no signal and the gauge drops to zero. I've cleaned the wiper and contacts twice, and the last time I saw one of the contacts was missing.

I wouldn't be hard to replace the sender if there was such a thing as a good one to swap in!
 

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With that contact missing the gauge will give you fits until the pump is swapped.
At least mine did. It lasted 10 years so I just bit the bullet and got a new pump.
 
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