Fuel Gauge not working
03-21-2017, 11:12 AM
#1
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2003 CLK500
Fuel Gauge not working
New to forums so don't know where to post this. I have a 2003 clk500 with 135k I recently bought. Everything is perfect on the car but I realized the fuel gauge doesn't work. It says it's full but I've drove it for more than 80 miles and it hasn't moved at all. Any clues on what it might be ?
03-21-2017, 12:42 PM
#2
MBworld Guru
There are several possibilities. One is a problem with the fuel sender unit. I doubt it's a stuck float, since there are two floats (because your fuel tank straddles the driveshaft) and the level is calculated by an algorithm that considers both readings. It could be a wiring issue, or a problem inside the sender unit (left side of tank), but again, it would mean both wires are a problem.
The wiring from the fuel sender goes directly to the rear SAM (a computer attached to the rear fuse panel). It transmits the fuel level readings over the CAN bus that are then interpreted by the instrument cluster. So, you could have a problem with the rear SAM or the cluster. There are some settings in the rear SAM and the cluster that determine the type of fuel sender installed (there was a change during MY2003 production). It's possible this is wrong in your car - maybe the prior owner had the sender replaced with a new style without proper coding, or the SAM or cluster was replaced without proper coding. I doubt it's the cluster, though, as you almost need to have that doen by a delaer with a new cluster part to retain the odometer.
SDS (Star Diagnosis) can do some test of the sender as well as verify proper coding. You may need to get it in service with a shop that has SDS. Of course all MBZ dealers have this, but a good indy might be less expensive and more careful with your car.
The wiring from the fuel sender goes directly to the rear SAM (a computer attached to the rear fuse panel). It transmits the fuel level readings over the CAN bus that are then interpreted by the instrument cluster. So, you could have a problem with the rear SAM or the cluster. There are some settings in the rear SAM and the cluster that determine the type of fuel sender installed (there was a change during MY2003 production). It's possible this is wrong in your car - maybe the prior owner had the sender replaced with a new style without proper coding, or the SAM or cluster was replaced without proper coding. I doubt it's the cluster, though, as you almost need to have that doen by a delaer with a new cluster part to retain the odometer.
SDS (Star Diagnosis) can do some test of the sender as well as verify proper coding. You may need to get it in service with a shop that has SDS. Of course all MBZ dealers have this, but a good indy might be less expensive and more careful with your car.
03-23-2017, 05:48 PM
#3
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2003 CLK500
There are several possibilities. One is a problem with the fuel sender unit. I doubt it's a stuck float, since there are two floats (because your fuel tank straddles the driveshaft) and the level is calculated by an algorithm that considers both readings. It could be a wiring issue, or a problem inside the sender unit (left side of tank), but again, it would mean both wires are a problem.
The wiring from the fuel sender goes directly to the rear SAM (a computer attached to the rear fuse panel). It transmits the fuel level readings over the CAN bus that are then interpreted by the instrument cluster. So, you could have a problem with the rear SAM or the cluster. There are some settings in the rear SAM and the cluster that determine the type of fuel sender installed (there was a change during MY2003 production). It's possible this is wrong in your car - maybe the prior owner had the sender replaced with a new style without proper coding, or the SAM or cluster was replaced without proper coding. I doubt it's the cluster, though, as you almost need to have that doen by a delaer with a new cluster part to retain the odometer.
SDS (Star Diagnosis) can do some test of the sender as well as verify proper coding. You may need to get it in service with a shop that has SDS. Of course all MBZ dealers have this, but a good indy might be less expensive and more careful with your car.
The wiring from the fuel sender goes directly to the rear SAM (a computer attached to the rear fuse panel). It transmits the fuel level readings over the CAN bus that are then interpreted by the instrument cluster. So, you could have a problem with the rear SAM or the cluster. There are some settings in the rear SAM and the cluster that determine the type of fuel sender installed (there was a change during MY2003 production). It's possible this is wrong in your car - maybe the prior owner had the sender replaced with a new style without proper coding, or the SAM or cluster was replaced without proper coding. I doubt it's the cluster, though, as you almost need to have that doen by a delaer with a new cluster part to retain the odometer.
SDS (Star Diagnosis) can do some test of the sender as well as verify proper coding. You may need to get it in service with a shop that has SDS. Of course all MBZ dealers have this, but a good indy might be less expensive and more careful with your car.
03-23-2017, 07:40 PM
#4
MBworld Guru
Hookup to SDS for diagnostics i generally bill ed on an hourly basis. Most shops charge an hour for that. I'd start there. But I'd definitely find a good indy that has SDS.
03-23-2017, 07:50 PM
#5
Replacement of the fuel sender unit is relatively easy and the sender unit itself isn't terribly expensive. The most complex issue is draining the fuel tank. which the brave or foolish DIYer might skip.
03-23-2017, 10:44 PM
#6
MBworld Guru
The problem with replacing the sender is that you have to disconnect its tubing from the pump. On my CLK, the pressure hose was pretty much welded on and would not release without breaking the nipple on the pump, thus requiring that they both be replaced. Total bill in discounted parts was close to $500.
