Hello, new to this forum. Hope you can help. Here is my story,
Wife was driving car when it stalled on her. I checked it out and got the car running, felt like it was fuel related because when I cranked it the car would sputter and die. Floored the accelerator and the car struggled at first but started and ran fine all the way home. Afterwards it would not start again. At first it would sputter really bad then die. But after a couple of tries it just cranks but no start. I scanned the obd2 and just received a miss fire: P0300-308. Nothing else showed. I changed the CPS and still no start. Cleared the codes and now nothing pops up.
I could smell gas from under the car so I checked the fuel pump. Sure enough it was leaking fuel. A small puddle was on the pump. Called Mercedes and found the car was under the extended warranty. Just to make sure I still tested the components, fuse was good, the relay was working, and I got voltage to the fuel pump connector (11+ volts) both with the relay and by using a jumper wire to give direct current. No operation was found. At this point it made sense that the pump had failed since the previous symptoms pointed to that. Now the warranty calls for a new tank which comes with a new pump pre installed. Got a call from the service advisor saying that the car still won't start. And if they want me to let them diagnose the car. I really don't trust the dealer. So I am picking up the car and towing it home since funds are tight right now and for the next couple of months. Unfortunately this happened on the same day I got out of the military (I was a diesel mech/USMC). I am going to make more troubleshooting steps and try to see what was missed.
Any advice on what I can look for? I am going to check all the fuses and relays again. could it be one of the control modules or ECU that failed? I would rather spend the money on a good Mercedes scanner than pay them. Which will cost the same. Any help will be appreciated. Thanks!

 

Let me also add that I was receiving a ESP malfunction return to workshop message that would go on intermittently a week or so prior and that the rear driver side air bag was starting to leak unless I left the car on the lifted setting. Don't know if this would cause the issues above. Thanks again.

 

You may want to check your Key FOB. Mine had problems starting and it turns out that my old Key Fob was not working. Got a new key from dealer (about $200) and it started right up.

 

Here is an update. I got car back from the dealer, new pump installed. I cranked the vehicle and check for voltage at the fuel pump connector. I am getting 10.6 volts when cranking and 11.6 when it is priming. But zero fuel pressure at the fuel rail connector. Will the computer not let the fuel pump operate even if there is voltage or could the auxiliary battery cause this issue? Having checked that yet.

 

Anyone out there?

 

So you get voltage to the fuel pump and still now fuel pressure? Well i know this sounds stupid but is there fuel in the tank? (it does happen)
Do you have any access to a diagnostic computer?

 

Fuel is at 3/4 full. I have a simple code reader. I haven't received any CEL since I cleared them.

 

I decided to trouble shoot again. Put a jumper wire where the relay is and I get 11.6 constant volts all the way to the fuel sending unit harness, new pump still does not come on. Checked ohms, suppose to be no higher than 100 measured from the positive and negative on the sending unit. I was getting .01 ohms. Pretty sure way below.
Now for the juicy stuff. Called the dealer, service advisor said old pump was working when they checked it before installing the new tank and that they checked the new pump saying that it was good also, claiming something is wrong with the car. I asked how did they checked test both fuel pumps, he didn't know. saying that the trained techs checked it. Called the manager, explained to him that everything sounds really suspicious. He asked if I requested a diagnostics which I didn't it was just a warranty repair. He said that they never should have checked the old pump since there was no request and that there is no protocol to test new parts pry to install. He too could not tell me how they test a fuel pump either. WTF!!!

 

I decided to trouble shoot again. Put a jumper wire where the relay is and I get 11.6 constant volts all the way to the fuel sending unit harness, new pump still does not come on. Checked ohms, suppose to be no higher than 100 measured from the positive and negative on the sending unit. I was getting .01 ohms. Pretty sure way below.
Now for the juicy stuff. Called the dealer, service advisor said old pump was working when they checked it before installing the new tank and that they checked the new pump saying that it was good also, claiming something is wrong with the car. I asked how did they checked test both fuel pumps, he didn't know. saying that the trained techs checked it. Called the manager, explained to him that everything sounds really suspicious. He asked if I requested a diagnostics which I didn't it was just a warranty repair. He said that they never should have checked the old pump since there was no request and that there is no protocol to test new parts pry to install. He too could not tell me how they test a fuel pump either. WTF!!!

 

Was vehicle operating properly on the way home from dealer after warranty repair, invoice narrative should document after repair test run & check for leaks. Nevertheless, contact MB http://mercedes-benz.custhelp.com/ to request warranty repair revisit inclusive of pulling fault codes at no cost to identify cause.

 

No the car wasn't running when I picked it up. It went in just for the warranty/recall on the fuel tank, which a new pump is installed as part the package. As I didn't request a diagnostics done they just did I the replacement. The issue I'm having is that they said the old pump was working and that they tested the new one poor to installation. I asked how they checked both and they couldn't provide an answer. Their manager said the testing should have never been done in the first place. I feel that I'm trying to be scammed, since the trouble shooting I did shows both pumps are bad. I just want to make sure that I did everything I could before I take the car back and they try to lie saying something else is bad. I've always done my own maintenance so I have very little experience dealing with someone else working on my car when o can see what they are doing.

 

They probably tested the fuel pump\ by putting 12 volts straight to pump. Very simple test to rule out faulty pump. Nothing suspicious about SA not knowing or Director not knowing as they aren't the techs but i understand how you feel since your vehicle isn't running, however that is most likely how they checked it.

So your vehicle wasn't running prior to tank replacement? By default you aren't going to get any diag done on vehicle since it is a warranty repair. If you drove your car into shop and it got pushed out of shop, then yes something fishy is going on. But if it was never drive-able prior to tank repl then nah, you have to fork out the money for daig.

Your vehicle may be flooded because you have been trying to start it so much.

Send 12 volts to your pump directly and try cranking vehicle. If it still doesn't start you need to start using star wiring and find out what pins on your ecu send a signal/voltage to your rear sam/pumps.

also check the wiring on the fuel pump top and make sure it correlates with the wires in the actual pump itself, sometimes from the factory they are backwards. causing pump to spin backwards, this has mostly happened on amg models but i wouldn't put it pass them to mess up a normal model as well.

You have a 113 motor correct? 16 spark plug plug wires?

 

Thanks for the response.
The motor is the 8 cyl. I did run straight volts to the pump by placing a jumper wire in place of the relay. I get 11.5v even if the key is off at the fuel pump wiring harness, still no pump operation. That rules out the relay and computer being bad. With the relay on it cycles as it is suppose to for a few seconds then shuts off. During cranking I get voltage as well.
Regarding the dealer, I thought it was weird that they said they checked the old pump as there was no request. Plus test a new one before install. The service manager said that too. On the new pump I ran a resistance test and I am getting .1 ohms. Average should be 50 ohms. Not to exceed 100ohms. I know the internal connector is plugged in because My fuel gauge is showing 3/4 full. At the fuel rail, gas barely drips out when cranking. I can't open the fuel pump cover because the dealer put a bar codes sticker on it so I don't want to break it and void the warranty. I just want to make sure I covered all possibilities before I go and have them fix the pump. Basically I don't trust their integrity, by them trying to lie to cover their tracks or get me to spend money so they can make a commission.

 

Understood, however just because your meter is reading voltage at rear sam, if that is what your are reffering to as your voltage reading, doesn't mean the pump is working, like physically working unless you can hear it. since you dont/cant open the pump I can't really tell you what else to do. When i said put 12 volts to pump, i literally mean get a battery or jumpbox, put jumper wires on the pins of the actual pump, and see if it cuts on. I only say to do this to rule out that the pump isn't mechanically faulty. If you applied 12volts straight to pump, and you can hear/see pump turning/cyphoning fuel then you have a issue with your ME or your pressure regulator may be having issues. You said money is tight, understandable, I am just not sure what else you could do to further diag without going inside tank. A 113 engine is produced from early 2000's to 2006, or around there. A 273 engine is the newer engine, not the newest, but the first 8 cylinder with coil on plug in Mercedes passenger cars. You either have spark plug wires or you have coil on plug. If you in fact have a 273 (coil on plug), next thing you could check is a voltage drop on pins 17 and 4 of the small socket on your ECU.... You should have 12 volts at ECU pins with key on engine off, during cranking it should drop to zero. If it doesn't you have a bad ecu.


I can't see you having a M273 though in a 2005 but it is possible. And you also said E500 so typically those are 113 motors.

 

did you ever fix the misfire issue???

 

Oh and btw, and just because you have voltage at rear sam, doesn't mean rear sam is sending voltage to fuel pump..... you need to check voltage at pump, your rear sam could be bad....

Your ecu sends a signal/voltage to your rear sam (relay) saying hey i'm trying to start, in turn the SAM sends voltage to your fuel pump. If sam isn't sending voltage to fuel pumps then you have a bad sam.... You can also check the connector on your rear sam for corrosion or bad contacts. You would need to look at star wiring for that though, connector view.

 

Thanks for the responses gents,

I thought I explained it earlier, I apologize. I have voltage going all the way to the fuel level sending unit with the relay on. It cycles as it suppose to and shows voltage when cranking. So I know the ME and SAM are working. With a jumper wire Inplace of the relay I get direct volts to the level sending unit which eliminates any computer control to the pump since there is voltage present even with the the key off. This tells me it's the pump.

Now for what the dealer came back at me with. They said that the way they tested both old and new pumps is by using their test equipment (not sure if it was STAR) to activate the pumps and they both operated. I called BS because I told them that I have ran straight voltage and there is no operation. And the pumps are non-feedback because the computers operate only the relay to activate the pumps. So I decided the hell with taking it back because they can say anything to not take responsibility. I'm going to open the tank and check the pump myself. Will let you know what I find out. Hasn't cost me anything yet just time.

 

Sorry about your dealership woes. However yes, open the tank and actually see the pump pumping fuel to the other side then let us know!

 

If it's not working, shouldn't it be under warranty? I thought they warranty all work for 12 months, 12k.

 

His car wasn't drive-able in the first place, so in theory negative. If it was something the dealership screwed up then yup, should be fixed on their watch.

 

SUCCESS!!!!!

I got the car working!!!
So it turns out that the harness connector prongs for the power and negative were pushed open wide when I put the testers of my multimeter on there. So when I connected it to the fuel sending unit, the fuel level was working but the pump was not getting any contact hence no power. I had to take the pump out to come to that conclusion. The pump's resistance was under 100 ohms, were it was suppose to be. This happened after the old pump had failed.
Obviously the dealer was full of crap saying that they had both pumps working with their test equipment since that would be impossible because of no power delivery. I called the manager and left him a message saying his techs were lying and they were just trying to make money off of me dishonestly!!!