Replaced fuel pump now rear SAM is bad?
 

A couple of days ago my 06 CLK350 would not start. It would turn over fine but not start. Had it taken to the dealership. They told me I needed a new fuel pump which made sense, however I did ask if they had checked the CPS sensor since it cuts off fuel and spark. They assured me that had been checked and the fuel pump was seized. Ok'd the replacement, they called later and said the car was running great, they just needed to complete the service (A or B) and I could pick it up the next day. The next day I get a call, they had done all the work the previous day and parked the car overnight. When they went to get it to wash it and get it ready for me to pick up, it wouldn't start. Now I am told I need a new rear SAM. I asked if the rear SAM controlled the fuel pump and was told yes, so I asked if the pump was really bad or they misdiagnosed in the first place. Was told both parts were bad. (Btw, I requested all parts removed be kept for me and placed in my trunk.) Is this a likely scenario? Is it likely the fuel pump went out and took the rear SAM with it or vice-versa? I know the SAM is a router of sorts but have never dealt with a bad one before. The car has low miles and I bought it new and it gets serviced regularly. Less than a year ago I put in a new battery. No CEL warning lights came on when it would not start. It has never not started, always turns over and starts very quickly. I appreciate any input, thanks.

It is possible that the SAM was bad all along, it's also possible that the SAM coincidentally died, but it's more likely that the shop damaged the SAM during this job. I'd push them until they at least cover the labor, and sell the parts at cost.

Thanks for that information Rodney. I suspected something was off when I was talking to the service rep and when I questioned him about why would the car be fine when they finished the work and not fine the next day, and did this mean maybe the fuel pump was fine but not working because the SAM was bad in the first place when he quickly discounted the SAM $150 without me asking for a discount. It will cost $600 now. He asked did I want them to go ahead with the repair and I asked what choice did I have? He actually had the nerve to say "Well, the car will start sometimes." I won't repeat here what I said after that, but I did commit to the job with the discount. $1100 for the fuel pump and now the SAM plus a couple of maintenance items. I did tell him this had better not turn into a cascade of failed parts, they better be right this time. He told me if any parts turn up bad after this they will pay for them and labor. So at least I have that guarantee. So for this repair at least the bleeding has stopped. I'm keeping the car for a weekend driver so I don't mind replacing parts for legitimate repairs. Do you know where the rear SAM is located on my car and what could they possibly have done to damage it? Thanks again, Mike.

:rolf::rolf::rolf::rolf::rolf::rolf::rolf::rolf::r olf::rolf::rolf::rolf::rolf::rolf::rolf::rolf::rol f::rolf::rolf::rolf::rolf::rolf:

MBUSA will warrant parts and labor for a year, so you have that.

Thanks Rodney.

Sorry insame1, I didn't realize your smilies were referencing the guarantee part, I just read your 1. and 2. sentences and took it the wrong way. Now I know they are on the bottom of all your post's. Sorry about that reply if you saw it, lol. I need to spend more time on here. Mike.

So I paid online and had an appointment at noon today to pick up my car and return the loaner. Service guy called at 10 am to tell me they had "issues" still and to hold off coming in.

I forgot to mention in my earlier post that when Roadside Assistance sent the flatbed to pick the car up the driver insisted on jump starting the car even though it would still turn over. He was a young kid and before I could stop him he tried to poke the live jumper cables under the battery cover which caused sparking. I told him to stop, and I removed the cover and he hooked up the cables and while the car turned over faster it would still not start. Maybe this caused the SAM to fry and other electrical issues? I've never had any type of electrical issue with this car before.

Yes, the jumping may be a big part of your problem. And not necessarily just that he tried before you removed the "cover." I put cover in quotes in that what you removed is not a battery cover, but the housing for your cabin air filter.

Hi Yidney - I stand corrected, you are right that what I referred to as the battery cover is the housing for the cabin air filter. Thanks for the other info too, it helps a great deal. Mike.

Yep, I'll bet that bad jump job caused issues with the SAM.

Hi Rodney - Thanks for that input. The dealership replaced the fuel pump first, then the next day when I was supposed to pick up the car they called and said they had trouble starting it and according to the tech I needed a new SAM. That was Thursday. The SAM was being shipped in and said it would be here Friday and I could pick up the car that day. I knew it probably would not be ready Friday, and it wasn't. On Monday I got an email with a link to pay the bill online, the repairs were finished, and to schedule a pick up time. I paid and I scheduled Tuesday at noon to pick up the car and at 10 am Tuesday I got a call that the car still had "issues." It is still there. Not only did the Roadside Assistance tow driver use live cables but there is a chance he crossed them up when he put them on. I remember him saying he thought the positive cable was always on the other side...so who knows what damage he might have done. And the needless thing about this whole issue is the car was turning over and didn't need a jump in the first place, but he insisted. I told him the car was not getting either fuel or spark or both but he didn't listen. I will never let anyone near my battery again unless I am very sure they know what they are doing. Will keep you posted. Thanks again, Mike.

m1, are you going to file a claim with the tow company or your insurance?

My fuel pump died a few months ago. The younger of the 2 tow truck guys suggested jumping. I said naw..... and it turning faster than it was didn't seem to me would help; the elder tow guy agreed. For mine, it just died while driving at 50.... gas reached 1/2 tank and the pump couldn't pump fuel from the other side of the saddle tank to the side that pumps to the engine. I guess if I had put 5 gallons of gas into the tank it would have started and I could have avoided the towing (flat bed).

It seems the tow company should be on the hook to assist with at least some of the cost.
Good luck.....

Was this Mercedes-Benz Roadside Assistance that tried to jump off the car? If so, Id call MBZ customer service and raise hell! Note that even if the roadside assist service cam out of the dealership, they report directly to MBUSA, not the dealer management.

Rodney - Thanks for telling me that, I did not know who legally hired the tow driver. The dealership is still trying to figure out what is wrong with the car. They said they have their shop foreman looking at the car and trying to figure out the "electrical" problem.

Fatz - I did have about 3/4 of a tank of gas, my car just wouldn't start one day, no warnings of any kind. I have already paid for a fuel pump and SAM, and they agreed any thing else is on them. It's odd the car worked fine after the fuel pump and SAM was installed, but when they went to get it ready for me to pick up the next day it had "issues." It was Roadside Assistance and the kid used live cables before I knew what he was doing. We'll see how it turns out.

So my service guy texted me around 6:30 pm yesterday telling me even though the car was starting fine every time, the tech didn't feel comfortable giving me the car and possibly getting me stranded this weekend. Not a big confidence builder. Will see what happens next week.

my car would give me an issue of starting once or twice a week with a "display malfunction visit workshop error" first told me its a fuel pump then said it was a bad rear sam...charged me 1300 and had the car for 2 weeks trying to figure it out..best of wishes to you

Did you finally get it fixed? Any other issues show up? Thanks - Mike.

Picked up car yesterday, mechanic said it was starting every time, drove it on errands yesterday and parked it last night, it worked fine. Went to start it today and will turn over but not starting. Waiting on Roadside Assistance to take it back to dealership.

Wow, that will make you doubt the car for as long as you own it. Still unclear if you told the dealer the jump story. They need to know that even if it's not to get your money back because it may affect where they look.

The service rep and mechanic both know about the jump. The mechanic said he traced the wiring harness and relays involved but didn't find anything and said the car was starting every time, but clearly it's not. Yeah, not a big confidence builder. At least the dealership is cooperating with me.

I just tried starting it with the spare key in case it has something to do with the key but no luck. If anybody has a clue what this might be I would appreciate the input. The battery is less than one year old.

It's easy enough to test the pressure on the fuel rain and amperage draw of the pump to rule it out. Of course if it is not being engaged during cranking, then it would be the CPS, or something electrical (the SAM or relay).

I researched the issue here on the forum when it first would not start and many results said to check the CPS first, I gave this info to the dealership the first day but don't know if they really bothered to check it. From my understanding a CPS going out or failing would cause these exact issues. I don't know how they would or could test a failing CPS other than just putting in a new one and seeing what happens. I have already paid for a new fuel pump and rear SAM. I don't think it could be the fuel filter because it either starts and runs fine or won't start at all.

The problem with CPS failure is it often does not throw an error. Today's dealer techs rely 100% on DTCs to decide what part to replace. The challenge in diagnosing CPS failure is that it mimics fuel pump failure. Without a signal from the CPS, the ECU shuts off the fuel pump as a safety feature (no CPS signal = no engine rotation, so no need for fuel).

There is a breakout box that can be plugged into the ECU that allows the tech to jump out the fuel pump so that is is energized regardless of engine running or not. If doing that causes the pump to operate and produce pressure at the fuel rail, then I'd say it's the CPS (or, though doubtful, the ECU itself). Unfortunately, most techs only understand how to read codes and swap parts - they have weak diagnostic skills and little understanding of how these electronic systems actually work.