Hey guys,
I've only owned my E55 a few months and already had to get it towed! Thanks to some random posts on MBWorld I was keyed into the different fuel pump relay in the AMG cars hidden on the right side of the trunk!

While I get the replacement relays in, and attempt to find a new socket to wire in, I was questioning if anyone has attempted any re-wiring of that circuit to make it robust. As it sits, when the car is idling the entire fuel pump harness going to the sender on the right side of the car gets warm to the touch. I was contemplating a few things if I can find all the right parts:

1. Just replacing the short section of toasted wiring on the fuel pump relay
2. Splicing in a second 10 ga wire after the 30 AMP fuse tied into a second OEM relay and run all the way up to the connector on the fuel pump. (it appears that the wiring leaving this relay is split at some point in the right rear of the car).

I should also mention that the fuel pump assemblies were all replaced with new sometime last year before I bought the car, so dirty filters shouldn't be a problem.

Any thoughts on this rewire? Anybody done similar?

 

 

im pretty sure that harness can be bought.

This happens because your fuelfilter is clogged and the pumps are drawing too much current. Replace the fuel filter assembly and pumps for peace in mind

 

I kinda mentioned in my post, but those assemblies are basically brand new on my car. I will open them up this week and confirm the filters are good, but they are shiney white, have the new splice harnesses with the new wiring configurations that have build dates of 2015 on them, and I have the receipts of all the work that was done in 2015.

I considered that the relay socket was charred from the previous pump assemblies and it just decided to corrode enough now, but the fact remains that the entire length of the wires is warm from the fuse through the relay, all the way up to the pumps.

Are you saying if your car is idling for 10 minutes, you can't feel any warmth from the wires by the pump?

 

https://mbworld.org/forums/mercedes-...ml#post6536637

The newly replaced pumps in my car draw 17 1/2 amps and it does create heat. Most likely the previous pump assemblies charred the socket and wires and they were never replaced.

FWIW, I am now measuring the current draw in the fuel pump circuit every oil change. Can't find the document or link but from the WIS, the current should measure up to 20 amps at idle. Above that, I say it's time to change fuel filters.

 

Nice, where are you checking the amps exactly?

 

I purchased an extra extender harness (the same one that is installed with the latest fuel pumps) and built up a box with two voltage/current meters (DROK meters in a plastic box).
At oil change, pull the rear seat, remove cover over fuel pumps, unplug harness, plug one end of the measuring device harness into the fuel pump connector, and plug the other end of the measuring device harness into the electrical harness in the car.
Upon "key on" I can see the voltage and current come online for about one second to pressurize the fuel rail, then the pumps turn off. Once the engine is turning over with the starter and running, the relay is re-energized and the device measures the voltage and current. About 13.5 amps on one pump and about 3.9 amps on the other pump. I log the info in the maintenance book, then remove the measuring device, reconnect harness to the pumps, install cover, install seat. Takes about 10 minutes which is far better than the hours I spent getting the car home when the old relay melted.

 

Is the relay problem illustrated in this post an E55 w211 problem? Or is it common to the E63 w211 also?