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  #1  
Old 04-27-2005, 12:42 PM
1988 300CE
 
Join Date: Apr 2005
Location: Sacramento, Ca.
Posts: 54
Crap! Gas gauge acting funny again.

Well, after replacing the float sending unit in the tank of my '88 300CE it's acting funny again. I thoug it was fixed. When I'm getting low on gas, below a quarter tank it jumps back up to about a third of a tank. It seems to jump around between the acurate level and about a third of a tank. I thought I had the thing fixed. What could possibly be wrong? On advise from the MB dealer, I banged the dash a few times with my fist and the needle in the guage didn't budge. So he said it has to be the sending unit. Any advise?

Also, the low fuel light comes on when a quarter tank is remaining. Is this correct. It seems early.

Thanks for you help.

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  #2  
Old 04-27-2005, 01:13 PM
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yal yal is offline
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I thought this usually happens becuase of a bad ground connection in the trunk near the antenna?
Someone please correct me if I'm wrong. Thanks.
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  #3  
Old 04-27-2005, 01:54 PM
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If it was a bad ground then wouldn't it happen at more random times? Not just when it is below 1/4 tank? I am guessing sender, but I don't have knowledge of that specific car. I searched and found a thread "300CE fuel tank problems" but it is a little unclear what it is talking about. Might help you.

Mike
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Last edited by mpolli; 04-27-2005 at 01:59 PM.
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  #4  
Old 04-27-2005, 02:16 PM
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Yeah, I have that too. Replaced the sender to no avail. Gave up.
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  #5  
Old 04-27-2005, 02:24 PM
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I had a similar problem that resolved after using some redline fuel system cleaner, available at pep boys. since you replaced sending unit, your problem may be elsewhere.
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  #6  
Old 04-27-2005, 02:27 PM
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Ditto. It wags all over the place below 1/2 tank, but the low-fuel light still comes on at the right time. I think it only happens while moving, so it seems it would be related to fuel sloshing around in the tank.
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  #7  
Old 05-28-2005, 07:03 PM
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I have a 1988 260E and the gas gauge works some of the time, then not at all for a while.

Any ideas?

Thanks!
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  #8  
Old 05-28-2005, 10:28 PM
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Hmmm...lots of us have this bouncing gauge problem but I've never seen a fix posted. Our '91 bounces. Our '90 does not.

I swapped the sending units between the cars and it made no difference. I tightened the big ground on the driver's side of the trans and it helped some, but it's still not right.

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  #9  
Old 05-29-2005, 09:36 PM
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I posted a fix that worked for me about 2 posts previously.

Quote:
Originally Posted by brewtoo
Hmmm...lots of us have this bouncing gauge problem but I've never seen a fix posted. Our '91 bounces. Our '90 does not.

I swapped the sending units between the cars and it made no difference. I tightened the big ground on the driver's side of the trans and it helped some, but it's still not right.

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  #10  
Old 05-29-2005, 11:57 PM
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Location: fort worth
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I have fixed my 124 sending unit when the needle used to bounce around.
Pull unit out. Remove small nut on bottom and the outer cylinder will slide off. Inside you will see 3 parallel wires and a float. Squirt the wires with carb cleaner and reassemble.
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  #11  
Old 06-13-2005, 09:31 AM
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Small update. I have been putting 1/2 quart MMO into every other tank of gas for the last 2 months. The fuel gauge problem is almost completely resolved. I think MMO slowly cleans the gunk off the sender parts without having to disassemble and risk damage. It took 3 treatments to start seeing a change. I've used this stuff in rotary engines, which are somewhat delicate, so I have no qualms using it in a Benz. This may or may not work for your problem, but it can't hurt to try.
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  #12  
Old 06-13-2005, 09:46 AM
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it's a sender issue...... this has been a Mercedes issue for more years than you care to know about...

has not effect on the operation of the car... does kind of drive you nuts...I had it happen on a couple of Mercedes..I just used it as an opportunity to fill up the gas...

Glad to hear MMO is helping.
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  #13  
Old 06-13-2005, 10:26 AM
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Quote:
Originally Posted by lee polowczuk
it's a sender issue...... this has been a Mercedes issue for more years than you care to know about...
I wonder why when I took the sending unit out of our '90 300E, which does not have the bouncing gauge problem, and put it in our '91, which does have the problem, it had no effect one way or the other. The problem remained in the '91 even with the known good sending unit.
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  #14  
Old 06-13-2005, 12:18 PM
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My 1991 300CE had the jumpy fuel needle usually between 1/4 and 1/2 levels. After reading the forum it seemed that there was no definitive fix even for those that replaced the sending unit. I started to occasionally use Techron and also keep the tank more often in the 1/2 to full area instead of my previous 0-1/2 full area and the problem went away.

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  #15  
Old 06-13-2005, 01:35 PM
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Mine does this as well on my W201. It has been posted on the 190Revolution forums that this is sometimes a ground in the cluster problem. Fixed by removing cluster and resoldering ground from the left side to the right side. Mine bounces under 1/2 tank, but if I tap the dash above the gauge it corrects itself for a few seconds. Basically long enough for me to see how much gas I have left. Mine will bounce all the way to a full tank and stay there when it only has 1/4 left! Too lazy to take the cluster out again as it is hot as hell outside....

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