My problem with my purchased brand new 2004 C240 started happening when the gas was reformulated with ethanol (I am guessing around 2009 after the warranty and accumulated 38k miles). Ever since, during the cold winter months when the gas companies flipped to their winter blend gas, I had to crank the car several times to get it started (it sputters and doesn't want to start). Once it is started, the car runs great throughout the day. Here is a brief description of what I tried to do to address the problem by my mechanic when my startup problem surfaced.

*cleaned MAF
*changed the battery
*complete tune-up (changed oil/coolant/transmission fluids and filters, gas filter, air & cabinet filters, plugs)
*changed Cam Position Sensor and Crank Position Sensor
*electrical voltages checked
*fuel pressure checked (monitored overnight for loss of pressure)
*tried using all the top-tiered (super grade) gas without any luck

I have brought the car in to a MB dealer and they suggested it "might" be a problem with the fuel pump with an estimated cost of $3k (at the time). However, the dealer will not guarantee this will "fix" my problem. How do I justify spending $3k and not addressing my cold start problem during the winter season??? Well, I couldn't and as of now, just live with the problem during the winter months. I am surviving by adding a bottle of Sea Foam every 2-3 gas fill-ups and managed to start the car in the winter morning. It gets cold in the SF Bay Areas, but it never freezing cold. The day when I can no longer start up the car, I will junk it......currently the car has around 80k miles. BTW, the car is always garaged inside and never left outside, and it runs great all day once it is started up in the morning. I was wondering if my problem has anything to do with the computer gadgets (software/firmware updates)? There isn't much I can do other than spend some money on the gas pump and pray it will fix my problem......which, I am still hesitating. It also seems there are lots of other owners complaining about this.

 

Try replacing plugs, coils and boots.

If that doesn't help then the fuel pump is a reasonable next step.

With average of 4,700 miles per year, why are you objecting to a $3k repair on an old car like this? Is junking the car a more attractive option for you?

 

The spark plugs were replaced......and the reason why I don't want to spend $3k for the fuel pump, there is "no" guarantee this will fix the problem. Currently, the car is barely worth much and all these years, I have managed to get by so far. There must be a problem somewhere else is my best guess.

 

No codes?
Does fuel pressure drop over night? what is it when you are trying to start Cold and have this issue?

When it starts fine what is the fuel pressure?

need to see if pressure is leaking down.
Or if pressure is low when you have this issue

See if this helps: Cold start -
turn key to on and sit for 5-10 or so seconds before turning key to start
This should allow fuel pump to build up appropriate pressure.

If it starts without issue doing this but not when you just quickly turn key - then pum pmay be issue.

Probably could find small indendant shop to change out cheaper.
Heck you could probably bu pump online and save money there too...

 

My mechanic tested the fuel pressure overnight and during the first start-up. He didn't see a problem losing pressure and thinks it "might" be a lazy fuel pump. Once the car starts up, it runs as perfect as it can all day long (multiple start-ups and driving).

In the morning, I have already incorporated turning on the ignition to the start position for 15+ seconds (without cranking the engine) and then "very lightly" prime the gas pedal a few times. I have found this helped. As for checking the diagnostic codes, both the MB dealer and my independent mechanic looked at it.

When I brought the car in to the MB dealer, they checked out the car and "guessing" it might be the fuel pump, with no guarantee at all. For $3k+ to change the fuel pump, I will definitely go to an independent mechanic to have it change for about a 1/3 of the price.

 

could be fuel pressure regulator leaking down too...

no sense throwing parts at it until proper troubleshooting...

again ask for fuel pressure numbers when idling... and have this issue.
@ next morning before startup

No such thing as LAZY fuel pump - they pretty much either pump what they are supposed too or they pump less over time until they do not pump.
could be the check valve that is supposed to hold pressure upstream is leaking down.
but id fuel pressure is normal in AM and has hard start something else is wrong which with all the engine sensors could be one of many things.

no sense pressing accelerator pedal as does nothing until engine started since you have fuel injection.
all it does is open throttle body to let air into engine.

Hard to help any more from my keyboard

 

The fuel pressure was checked overnight by my mechanic and said it was ok. Even at the MB dealer had it check and didn't think that was an issue (nothing written in his report). Once started, the C240 will run normal and fine all day long.