fuel gauge question - PeachParts Mercedes-Benz Forum

kanadary · #1 02-21-2003, 02:08 PM

I am wondering if anyone else out there has had this happening. I have a 87 190E-2.6, the odometer died at 100K miles, but now the fuel gauge after i finish gassing up the car will go up to full very slowly or sometimes it will stay at the before filled level and will eventually move up after a minute or so. not sure if i am in for replacing the sending unit soon or what. any info would be appreciated. thanks Ken

crookednose · #2 02-23-2003, 01:34 AM

The fuel sending unit in the fuel tank probably just needs cleaning. It was about a 30 minute job on my 190 1987 2.0L

kanadary · #3 02-25-2003, 10:32 AM

thanks. i will try it. is it easy to access? thru the back seat? Ken

Potomac Pat · #4 02-25-2003, 10:34 AM

Access the fuel sending unit from in the trunk.

kanadary · #5 02-26-2003, 10:24 AM

do i have to change the seal or buy anything? if i need to i will buy it prior to working on it. which part do you have to clean out, or is it self explanatory once i access it? ken

csnow · #6 02-27-2003, 03:57 PM

There is a gasket involved.

yamil78 · #7 02-28-2003, 10:57 AM

I have been experiencing the same exact problem with my '99 E-320. I fill up all the way (I know its all the way because the gas pump stops itself and I keep trying to pump more gas in; 3 - 4 stops).

I am wondering if it is the same exact issue. Let us know if you get it fixed by changing or cleaning the fuel sensing unit.
I would be interested in knowing how it is done and what materials are needed to do it.

Thanks dude

yamil

haasman · #8 02-28-2003, 11:18 AM

Someone posted recently that using a bottle (or two) of a fuel system cleaner solved this for them. Often better to do with less than a full tank for a higher ratio of cleaner to fuel.

Keep us posted,

Haasman

kanadary · #9 02-28-2003, 11:31 AM

i will take it apart this weekend and clean it. haasman, so is one option to dump a couple of can of fuel cleaner in the tank or do you use the fuel cleaner to flush the unit after you remove it?

haasman · #10 02-28-2003, 12:16 PM

Ken

What the posting said was you do not have to remove it, that the fuel system cleaner got rid of all the accumulated varnish etc. and the unti returned to normal. The side benefit of course was a fuel system cleaning. Often it is recommended that you change your oil and filter soon after doing this since it tends to wash a lot of crud down into the engine and engine oil.

If you do have to remove the sending unit and needs to be taken apart, be aware that there are very fine (small) wires that the fuel sending unit float rides between that transfers the fuel level. Often these just get dirty and need to be cleaned.

The last unit I cleaned was out of a diesel, I pressume the gas ones are similiar. Whe you extract it from the fuel tank it will have fuel inside it so beware that it will need to drain for a few minutes. Once out you will need to take a tiny nut off the top (?) or bottom to be able to remove the outer tube from the inner section of the tube. The you will be able to see the float, the wires etc.

Not only the wires need to be cleaned but also the contacts at the bottom of the float AND the contacts at the lowest part of the travel that turn on the low fuel warning light.

Additionally, the fuel sending unit head is a very large nut size. Often either large channel locks or large crescent wrench will help start the turning and removal of the sending unit. It is always a good idea to replace the gasket that goes between the unit and the tank.

Hope this helps, keep us posted,

Haasman

kanadary · #11 02-28-2003, 12:25 PM

thanks that is very helpful. i think i will try the cleaner method first then see what happens. like i said, its not like its not reacting so maybe a good cleaner will work. Your 65 911 is pretty rare. i had a 65 356 C.

kanadary · #12 03-24-2003, 03:04 PM

well i dumped in two bottles of fuel injection cleaner into half a tank of gas, Wynn's i think, and nothing happened but now that its been a few weeks later the gauge seems to be responding faster. at first it would take about 1 to 2 minutes before it would register full, this morning it only took about 10 seconds. i will see later on this week if the trend continues. i drive about 70 miles to and from each day so i get to try this often

haasman · #13 03-24-2003, 04:14 PM

Ken

Sounds like a gummy sending unit if after the fuel cleaner it is starting to improve. The ratio of fuel to cleaner is important.

Also consider pulling the sending unit.

Thanks for keeping us posted,

Haasman

yamil78 · #14 03-25-2003, 09:24 AM

I have been trying this same approach and it seems to work for me too. LIke I mentioned in my earlier reply, I was having this very same problem with my gas gauge. I have actually dumped about four bottles of fuel cleaner at it (2 bottles per tank) and just like THAT!!!! it has gradually started to go away.
So I guess it must work!!!!

kanadary · #15 04-15-2003, 10:58 AM

Here's an update. The other day the response time for the gauge was starting to lag again so I put another two bottles of fuel injector cleaner into half a tank and drove it till the low fuel light just started to light up. I filled it and this time the gauge didn't move up all the way, it only moved slightly to the point where the light was off.
I just removed the sending unit last night and yes its very easy to remove. Just unplug and remove that big nut. There is a small hole in the aluminum tube that will allow the fuel to drain out as you remove it, takes about a minute or two, depending on how much fuel is in the tank. Access from the trunk is very good.
Once I got it out, I didn't see any nuts or screws or anything that the others have posted about diesel sending units so I assume they must be different. What I did was straighten out the three tabs/crimps at the base of the sending unit and ease out the black plastic cover to access the float and contacts. That was a far as I could dismantle. The top of the sending unit was crimped in pretty well and it didn't look like it would come apart easy. I took a bottle of Valvoline carb cleaner and sprayed the float, the rod that the float rides on and everywhere I saw the "yellowish" residue. I musta used about half the bottle and got it to the point where when I would slightly tip the unit upside down the float would start moving, when I first started the float wouldn't even move when it was upside down unless I jerked it slightly. I put it back together and put two new O-rings on the nut and tried it out. It responded right away and this morning when I filled up it worked right away. If anyone knows how to remove the top of the sending unit subassembly from the whole unit, I would be interested to find out, but as it stands now, its working and hopefully it will for awhile. Total time about 30 minutes. I went to http://www.carpartstogo.com/ for the O-rings, about $5-6 for the two and they do sell the sending unit for about $70 for the 190. Ken

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