Hello everyone, new here and I want to thank anyone in advance for providing their insights.

I have a 2007 C280 4matic (W203) with the M272 engine and it won't start. Sorry for the length, just trying to be complete in my problem description.

The "what happened":
1. Earlier in the day, I drove the car and engine was running, it was smooth and strong, no weird idle or low power.
2. Wife was driving the car, stopped at a stop sign, proceeded and car was sluggish (maybe 150 feet) car died and would not restart.
3. After waiting a long period of time (say overnight) the car will start up for about a second and then shut down. It does this one time and you have to wait a long time to get it to do it again.

What I have looked at:
1. Lights come on and the engine turns over fine, solid power.
2. Used a Bosch OBDII reader to look for codes, it reports no DTCs.
3. Used a iCarsoft i980 multi-system scanner, it reports a lot of little issues (i.e. RR door power circuit open), it isn't reporting any real issues that I see.
4. I read that the CPS (crankshaft position sensor) can be in partial failure and sometimes the car won't report it as a fault, but it can still cause intermittent failures. I replaced the CPS just in case, DC measurements of the new part were within 1% of the old part; new part installed and no change...car won't start. (...as an aside, wow to the team at MB that agreed on that sensors placement).
5. I have noticed that the OBDII has trouble connecting more often than not...makes me worry about the computer.

Note: Since the car will start for about one second and then shuts down, I have a strong suspicion that this is a electronics issue...I am worried that it does not seem to give a code for a failure though.

History:
1. I have replaced the steering wheel multi-function switch about a week prior to this incident with the car being driven daily. I used the iCarsoft to look at the functionality of this switch and it actuates as expected for all settings.
2. A month ago I replaced the transmission valve body/conductor plate, connector, and associated filter, fluid, gasket.
3. Six months ago I replaced the AC system (easier to just say system than write all the parts).

My gut points to the steering wheel multi-function switch replacement having caused an issue...but the car drove fine for week...no issue with the airbag (per the iCarsoft).

Question:
1. Will the car run if it has an issue with the airbag?
2. What are common failure signs of the computer...or is that what I am seeing?

 

After the car starts and shuts down, do you see any DTCs or pending codes with the iCarsoft i980?

I'm not familiar with the MB nuances. But, in general, an air bag circuit failure will not prevent a car from running.

 

If your battery is good you have to check fuel pressure as step number one.

 

No, nothing major on the iCarsoft

Good to know about the airbag, thank you.

 

Hey Holmes,

Good call on the fuel pressure! With the key in position 2, (this is where I would expect the pump to have the rail primed) I read zero pressure with my gauge. I'm not ashamed to use cheap tools since I'm not a pro, so I did a sanity check and with a face shield on I pressed the Shrader valve with a small screw driver...nothing!

So, it looks like there is a fuel delivery problem. What I am curious about though is why aren't any of the scan tools detecting this as a problem?

I did a quick read on the fuel pump replacement...doesn't seem too bad. I will say I was pleasantly surprised to hear that MB put an access panel under the rear seat. After the adventure of getting to the CPS sensor I was sure the fuel pump was going to be ridiculous.

Are there known issues with the W203 and fuel delivery? I only ask because it seems like everytime I need to repair something the first statement I hear is, "...this is really common".

Cheers!

 

Fuel pumps are known to go out on these cars. You can probably wake it up by tapping the top of the tank with a rubber mallet. There's rarely any faults triggered.

Make sure you're getting power at the pump before you go replacing it. It would suck if it's just a simple relay or something. I'd also recommend doing the fuel filter.

 

Okay everybody...what is the magic key to get the fuel line off of the pump? Apparently the '07 is slightly different. I got the clamp off...it was not a Clic-R type either...it was a permanent clamp. That fuel line has to come off to get the pump out...

 

The black shroud has the look of an ML style fuel line clamp, but there is not latch or slide...

 

Found it! Wow. So, where my finger is in the photo rotate towards the connector shroud and squeeze with my thumb on opposite side, then gently pull upward.

Nothing like a little mechanical piece to make me feel dumb for the day.

FYI, when connected to a 12V power supply the pump does not turn on. Thankfully I believe I have found the source of my troubles. Thanks again Holmes!