Lazy fuel gauge

Greybeast · 5th June 2006, 05:21

When fuel tank is nearing empty (say less than 1/4 tank) it reads lower than than it should when first starting out. After driving a bit, maybe 10 or 15 minutes, the needle slowly rises to the actual level and settles there. Sometimes the low fuel light will be on initially and disappears as the needle rises to the correct level.

I'm a new owner wondering if this is a normal occurrence. Thanks.

GB

E55AMG2 · 5th June 2006, 05:32

perfectly normal, if you're in doubt you can enter the OBC test mode, test #6, and see the level in liters.

jclyman · 5th June 2006, 13:54

I have long suspected that my "range" drops after the car sits overnight. Many, many times I have shut the car off without any fuel light, and when I start a few days later, the fuel light is ON. I had figured the fuel in both tanks equalized their levels (from having more fuel in the right side one), but I didn't understand why that would show on the fuel gauge. (I thought the car was "smarter" than that.)

03BeastCharmer · 5th June 2006, 15:44

I’m having the opposite issue. When I fill the car up it only reads ¾ full, and the OBC gives me range that is consistent with that. Over the next two days (approx 40 miles), it will slowly go to full. This started about a month ago, and 1st I was almost empty and it read ½ tank. From the miles I’d driven, and it showing ¼ tank the night before I knew I needed gas. When I filled up, that’s when it started this ¾ full when really full.

This happen to anyone else?

andye39s · 5th June 2006, 19:45

It's the fuel level sensor. My car is in right now to replace the sensors (2 of them).

Second time this happened. First time it was stuck on empty after fillups, until the car gets restarted. This time, from a 1/4 tank, it slowly went up to 3/4 tank, then this morning after fillup it was stuck on empty.

03BeastCharmer · 5th June 2006, 21:25

Quote:

Originally Posted by andye39s

It's the fuel level sensor. My car is in right now to replace the sensors (2 of them).

Second time this happened. First time it was stuck on empty after fillups, until the car gets restarted. This time, from a 1/4 tank, it slowly went up to 3/4 tank, then this morning after fillup it was stuck on empty.

I assume the fuel level sensor is in the gas tank? So should I go in just after a fill up to prove the problem or with an almost empty tank to make getting at the sensor easier?

andye39s · 5th June 2006, 21:38

You don't have to. The car's computer will register a fault code if there's any funny reading from the two sensors. Once the dealer sees the code they'll replace the sensors.

My SA told me there 2 sensors. Something like 1 reads the upper half and the other reads the lower half. Average the two readings and that's your fuel level.

I don't know how and wehre they replace the sensors. both times I brought my car in with a full tank, and I pickup the car with a full tank. So I don't suppose they had to drain it or anything, unless of course they drained it and put it back. They better, it's $55 for every fillup!

Quote:

Originally Posted by 03BeastCharmer

I assume the fuel level sensor is in the gas tank? So should I go in just after a fill up to prove the problem or with an almost empty tank to make getting at the sensor easier?

DownSouthM5 · 6th June 2006, 20:27

Same issue this week with mine. Fuel level sensor issue, makes the gas gauge go wacko. Dealer is replacing this week under warranty. There were stored fault codes when they checked it out.

patrick