Need help: fuel pump issue
Thread Starter
Super Member
Joined: Mar 2007
Posts: 946
Likes: 1
From: Bay Area
03 C32 gone, 06 CLS55, 16 Tesla X
Need help: fuel pump issue
So my car won't start, there is no fuel pressure in the fuel line
Fuel pump does not make noise or pump when key is on/crank
I have
replaced new CPS (of course won't fix)
checked the relay (A) and fuse 4 (20). They are all good
already remove the seats and caps to access both left and right side unit
Can both be bad at the same time?
Can someone please tell me how to check for both unit? (which wire should have 12V+ when key is on or crank?)
There are 1 plug on the right (4 wires, brown-red/blue-brown-red/blue) and 2 plugs on the left (1 small-3 wires gray/brown-green/brown-red/yellow and 1 bigger plug-3 wires green/brow-blue/white-blue/black )
Much appreciate!
Fuel pump does not make noise or pump when key is on/crank
I have
replaced new CPS (of course won't fix)
checked the relay (A) and fuse 4 (20). They are all good
already remove the seats and caps to access both left and right side unit
Can both be bad at the same time?
Can someone please tell me how to check for both unit? (which wire should have 12V+ when key is on or crank?)
There are 1 plug on the right (4 wires, brown-red/blue-brown-red/blue) and 2 plugs on the left (1 small-3 wires gray/brown-green/brown-red/yellow and 1 bigger plug-3 wires green/brow-blue/white-blue/black )
Much appreciate!
MBWorld Fanatic!
Joined: Nov 2014
Posts: 1,139
Likes: 77
E55
You are checking the wrong relay(s) and fuse. Those locations are for non AMG. You should have at least 1 but probably 2 fuel pump relays behind side trunk panel on the passenger side. On the passenger side fuel sender connector the Browns are ground and reds are power. 1 set for each pump. They should have battery voltage briefly when turning the key on and constant when cranking.
Thread Starter
Super Member
Joined: Mar 2007
Posts: 946
Likes: 1
From: Bay Area
03 C32 gone, 06 CLS55, 16 Tesla X
I checked relays on the rear SAM driver side. There is anotherone fuse box under the trunk carpet right next to the battery. Did not know there is one on the passenger side?
Thanks Rocman8!
MBWorld Fanatic!
Joined: Nov 2014
Posts: 1,139
Likes: 77
E55
Well it's not actually a fuse box it's more like just an empty space they used to place them. Just because you have voltage doesn't mean the relays and/or wiring connections are good. If the contacts are burnt you may have voltage but under a load it will not be able to carry a current. Access them and check the contacts and replace the relays. You HAVE to start here if you don't have fuel pressure and you do have voltage.
Super Member
Joined: Jan 2007
Posts: 979
Likes: 38
From: South Africa
2018 E63s AMG (Current) 2011 CL63 AMG (Sold) 2005 CLS55 AMG (Sold) 2004 C32 AMG (Sold)
If you have voltage when cranking and no fuel pressure then it's more than likely the fuel pump. Just replaced mine 
MBWorld Fanatic!
Joined: Dec 2006
Posts: 1,125
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From: Florida-Germany-New York
2004 E55,1969 300SEL6.3,2011 ML350 BlueTec Diesel,2005 ML400 CDI
If you have access to XENTRY DAS you can turn the pumps on via the actuation option. It should then be relatively easy to locate the problrm
