C55 cranks but won't start - fuel issue? - need help quick
Thread Starter
Junior Member
Joined: Oct 2009
Posts: 18
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From: Jacksonville, FL
2006 C55 AMG
C55 cranks but won't start - fuel issue? - need help quick
I have a 2005 C55 AMG with 74,000 miles. The engine turns over but won't start up, so I had it towed to local Mercedes dealer to diagnose. Service adviser said what sounded like "SIM" but after researching the forum, I think he was saying "SAM" was corroded, causing two rear fuel pump relays to stop working, hence no fuel getting to motor, causing it to turn over but not start. They quoted me $2100 to fix!!
Does this sound right? I need someone on the forum who has some mechanical and electrical knowledge on the W203 chassis to chime in. I told them to hold off, but I can't keep them waiting long, so I need some advice. Who knows what this SAM thing is? Is it all electrical or anything mechanical that they are talking about? What are the rear fuel pump relays they are talking about? Doesn't sound like the fuel pump in the tank is involved, which I thought was probably the issue, but apparently not.
Does $2100 sound like a ripoff? Once I know what the SAM and rear fuel pump relays, I'll have a better idea of the cost I was quoted. Is this something simple to fix? I am a bit mechanically inclined, is this something I could do with the right tools?
Need advise ASAP, and thank you for any help!
Daniel
Does this sound right? I need someone on the forum who has some mechanical and electrical knowledge on the W203 chassis to chime in. I told them to hold off, but I can't keep them waiting long, so I need some advice. Who knows what this SAM thing is? Is it all electrical or anything mechanical that they are talking about? What are the rear fuel pump relays they are talking about? Doesn't sound like the fuel pump in the tank is involved, which I thought was probably the issue, but apparently not.
Does $2100 sound like a ripoff? Once I know what the SAM and rear fuel pump relays, I'll have a better idea of the cost I was quoted. Is this something simple to fix? I am a bit mechanically inclined, is this something I could do with the right tools?
Need advise ASAP, and thank you for any help!
Daniel
Thread Starter
Junior Member
Joined: Oct 2009
Posts: 18
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From: Jacksonville, FL
2006 C55 AMG
No, I'm a relatively new C55 owner, so I'm not familiar with all the common problems they may have. I'm assuming CPS is the crank position sensor, correct? Is a CPS going out a common failure with these cars? Where is the CPS located?
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From: Canada
eclectic assortment of cars
Issues with the crank position sensor usually exhibit as trouble hot starting or sporadic starting. It's fairly common, but the part isn't very expensive (generally under $100). The CPS is located on the block, near the transmission bell housing, on the driver's side. It's only held in with one bolt, but it can be a bit of a squeeze to get in here.
I would think that if the techs at the dealer hooked the car up to Star diagnostics, it could diagnose the CPS? Not sure though, I haven't had first hand experience with the factory diagnostic tools.
I would think that if the techs at the dealer hooked the car up to Star diagnostics, it could diagnose the CPS? Not sure though, I haven't had first hand experience with the factory diagnostic tools.
Thread Starter
Junior Member
Joined: Oct 2009
Posts: 18
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From: Jacksonville, FL
2006 C55 AMG
Thanks for the info guys, I will bring it up with the service adviser on Monday. However, I would also like to solicit for more information about this SAM unit and the rear fuel pump relays.
What is the SAM unit? What does the acronym S-A-M stand for? Where is it located? Would the computer diagnostic specifically point at the SAM unit if it went bad?
What and where are the "rear fuel pump relays"? I've never heard of any car having "rear" fuel pump relays...and even if it does, and even if they went bad, where is this $2100 repair cost come from? Does the SAM unit and rear fuel pump relays that expensive, or are they that hard to get to that labor is that expensive? That quote sounds ridiculous to me.
How could a Mercedes with only 74,000 miles get enough corrosion on the SAM to make it go bad? Chevrolets aren't that unreliable! I can't help but have the feeling that I'm getting screwed by the dealership.
Thanks for any advice.
Daniel
What is the SAM unit? What does the acronym S-A-M stand for? Where is it located? Would the computer diagnostic specifically point at the SAM unit if it went bad?
What and where are the "rear fuel pump relays"? I've never heard of any car having "rear" fuel pump relays...and even if it does, and even if they went bad, where is this $2100 repair cost come from? Does the SAM unit and rear fuel pump relays that expensive, or are they that hard to get to that labor is that expensive? That quote sounds ridiculous to me.
How could a Mercedes with only 74,000 miles get enough corrosion on the SAM to make it go bad? Chevrolets aren't that unreliable! I can't help but have the feeling that I'm getting screwed by the dealership.
Thanks for any advice.
Daniel
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Joined: Jan 2009
Posts: 327
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From: Isla Verde, Puerto Rico
SRT-6
Another part that causes the same symptoms in the R170/SRT-6 is the RCM. (Relay control module) Lots of them end up with cracked solder joints and the end result is the crank with no start symptom. They can be re-soldered if your handy. Googling around it seems the C55 SAM is the equivalent and is $352.00 on amazon.
Les
Les
Last edited by Velociabstract; Mar 22, 2014 at 07:42 PM. Reason: link to the part
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From: Edmonton
2003 C32 AMG
A SAM unit is a Signal Acquistion Module, its basically the fuse box. Some cars have a front and rear SAM. It shares information on the CAN network with the ECU, and is a computer controlled fuse and relay box more or less.
Yes the SAM unit is expensive to replace, but I don't know about $2100.... dealers always mark it up big time.
Yes the SAM unit is expensive to replace, but I don't know about $2100.... dealers always mark it up big time.
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1999 E320 4matic Wagon, 2005 C55 AMG - sold, 1998 VW Jetta TDI - sold, 2006 C230 Sport - Totaled :(
Man, $2100 
Did you ever figure out the problem? If not:
Crank Position Sensor from rmeuropean.com = $45, throw in maybe some wiper blades or something else cheap to go over that $50 mark and get free shipping. Regardless of whether it is this or not, you WILL have to do this at some point (they are pretty much guaranteed to fail), probably before you get to 100k miles (I did mine around 85k or so).
And as far the dealer, there is a reason it's called the STEALERship. If anything, go to an Indy that knows how to work on German cars, much cheaper. Or if it is the SAM, you can replace that yourself. It's behind the driver's side rear tire in the trunk, just pull back the liner.
Good luck
Did you ever figure out the problem? If not:
Crank Position Sensor from rmeuropean.com = $45, throw in maybe some wiper blades or something else cheap to go over that $50 mark and get free shipping. Regardless of whether it is this or not, you WILL have to do this at some point (they are pretty much guaranteed to fail), probably before you get to 100k miles (I did mine around 85k or so).
And as far the dealer, there is a reason it's called the STEALERship. If anything, go to an Indy that knows how to work on German cars, much cheaper. Or if it is the SAM, you can replace that yourself. It's behind the driver's side rear tire in the trunk, just pull back the liner.
Good luck
