Glyn M Ruck

There is a lesson in there somewhere

Pleased it's fixed. I did not realise you were running an aftermarket filter.

d1no

Yeah I actually thought it was a rebranded oem filter but I guess it wasnt, but maybe even they fail sometime.. Oh well I'm just happy it was nothing expensive. And the check engine light disapearred byitself. So it was probably related to the fuel filter change

Glyn M Ruck

You probably got a CEL because the ECU was battling with fuel trim with pressure all over the place. It takes a few drive cycles to settle properly.

Milkm4n

just bought the cps sensor for an o7 230 with an m272 engine, the newest part number for the cps is A6429050000 just thought i would share

attila518

Hi
Sorry to ask about an old thread, but your problem is so similar to mine.
I get full 55psi @ idle and surge to 55 and steady @ 10-15 psi when key turned on without turning over. Car only starts rough first thing in the morning ONLY. Then fine the rest of the day. However it does stumble when warmed up at lower idle once in a while.

attila518

Hi
Glynn I'm a new member and I saw how knowledgable you were with D1no's
c320 hard start. Wondering if you have any suggestions for me?

LILBENZ230

By "starts rough" do you mean it gives a little bit of a sputter? If so you're not alone with the C230.. I've never been able to figure out what it is, I just don't worry about it anymore.

mlee1951

i am having a very similar problem....decided to have the car completely serviced (meaning all fluids-oil/transmission/coolant/brake, filters-air/gas/cabin, plugs, crank sensor, cam sensor, and even the valve cover gaskets because of a leak). and the problem is still there. it usually take a few tries to start the car. once the car starts, the car runs just fine and without any problem.

prior to this problem, i had the check engine light on and the mechanic checked the code and said he will clean the MAF. after cleaning the MAF and resetting the error code, car ran fine. when this cold start problem started, i thought it was the extreme cold weather or the original battery that was causing the problem. so, i had Sears check out the battery and the charging unit, and it was fine. since the battery is long overdue, i changed the battery. oblivious, this didn't help much because the problem was still there.

I am going to go back to the mechanic and have him take a look at the MAF again. I don't know what else to do. maybe the OS sensor, or something else. pretty frustrating problem. if any expert has any suggestions, please send me a message....will greatly appreciate it.

This morning, the car started without a problem. I turn on the car, waited a couple of seconds before turning on the ignition. Will retest tomorrow morning and see what happens.

jtwillia2

Not sure whether or not this has been suggested in this thread, but I had a rough start/idle problem and I tried several different things like fuel filter and spark plugs before finally solving it by thoroughly cleaning my throttle body. See my thread on the details here.

mlee1951

i will ask my mechanic about cleaning the throttle cable. btw, i did change the gas filter as part of my "big" service. going back to my service records at MB, i wasn't sure if they ever changed the gas filter.

this morning, the car start fine....i think i turned the car to on and then waited for a second or two before turning on the ignition. seems to help....will retest tomorrow. thanks for the info.

jtwillia2

throttle body, not cable. It's something that must be removed from the car. Check out my thread about cleaning the body itself and also the electric internals.

mlee1951

thanks for the corrections....i will look into your thread to find out more details.

mlee1951

I just reported the same problem....in addition to a major tuneup (plugs, all the filters and fluids), the mechanic also changed the crank and cam sensors. And I still have a problem starting the car in the morning. Can I ask you what you did to address your starting problem?

dbcooper

My inlaws have a 2005 C240 wagon with the M112 engine. Last winter during the coolest weather, the car exhibited the hard to start condition first thing in the morning or when they would drive home late at night. The car might take several minutes of separate cranking attempts to finally start. I cleaned the MAF sensor around the same time the weather got warmer and the problem disappeared. This winter the problem has reappeared. I pulled a spark plug wire and there is spark. Next a spark plug was pulled and it was evident that is was soaked in fuel. What I found was that if I removed the fuel pump fuse (#4) and let it crank, the engine would sputter to life for a few seconds. If I started it cranking and then plugged in the fuel pump fuse the engine would catch and run fine.

It appears my next step is to get a fuel pressure gauge and see how much pressure is lost after the engine is shut down. Leaky fuel injectors, Cold start injector for this engine?, if the injection getting a wrong signal and just flooding with the initial cranking? Enquiring minds want to know?

Hope this information helps someone else with this problem. Once I get the tools and the car in the same place I can do more testing.

mlee1951

My mechanic tested the fuel pressure and said it was fine. During the cold morning, my car has a very tough time starting. However, if i try to start my car during the late morning (near noon) when it's not as cold, it starts up good. I am beginning to suspect it might be the type of gas i used. Recently, I filled up with Rotten Robbie super gas and my car started to have problems with the cold morning start. Since then, the last couple of times i have since filled up using Chevron and Shell super and hoping it will eventually get my car running right again in the morning.

dbcooper

The cold star problem may be affected by winter blend gasoline as well as outside temperaure. I can report that my inlaws car only gets super unleaded from Chevron. I am not convinced brand of fuel is a major variable. I still have not gotten the car back from them to test their fuel leakdown pressure. The weather has been warmer 50's and 60's morning or night and the car starts sooner.

mlee1951

Lately, just prior before going to sleep, I start up the car at night and let it run for about 30 seconds. Now, in the morning after sitting in the garage for 10+ hours, the car starts up without much problem on the first crank. I noticed that the C240 can sit in the garage for over 14 hours and starts up just fine in the late morning when it isn't as cold.

FYI, the car runs just fine after it starts up. I can still drive the C240 to work and let it sit for over 6 hours and it'll start right up.

Glyn M Ruck

Good cold starting on a gasoline engine needs:

Good winter gas with more light ends
Ignition system up to snuff including plugs
Fuel System up to snuff ~ fuel pressure >3.8 bar or 55 psi ~ Run some Techron Concentrate to make sure injectors are clean
Obviously compression
No restrictions air cleaner or exhaust
And proper open loop mixture enrichment. This is dependent on the temperature sensor giving accurate information to the ECU on engine temperature.

mlee1951

I have thought about adding a gas treatment to my next fill-up. Is this Chevron Techron Concentrate safe for the C240?

I don't know if my mechanic checked out the temperature sensor when he was trying to diagnose my cold winter start. One of his last comment was that I may have a lazy gas pump.

samaritrey

Techron is the only fuel additive approved by Mercedes from my understanding.

mlee1951

thanks for the info....appreciate it.

Glyn M Ruck

+1^ Techron is fully approved as is BASF now. BASF is equally fine ~ Eeerm! I'm not allowed to talk about that. Doubt you will find the BASF material outside Europe.

Check your fuel pressure. That will soon tell you if your pump is OK & filter not blocked/semi blocked. The pressure check Schrader valve is on the front fuel rail that connects the injectors to one another.

mlee1951

I will have my mechanic look into it again. During my last service, he rechecked all the voltages and the fuel pressure. He said the fuel pump is ok and not losing pressure. In addition to that, he told me the car may have a "lazy" fuel pump. Changing the fuel pump won't be cheap he told me. :-(

Shawn K

I have 2003 c240 and replaced both fuel pump and fuel sending unit and fuel filter and car runs perfect but the car stops and shuts off with half gas tank, and when I put gas in tank it starts and runs again, I have to fill up my gas tank when It is getting close to 1/2 tank.
I have long cranking problem too, it is not usual time for start when I am starting my car,
please let me know if you have any idea.

mlee1951

when i brought the car to the dealer, they told me that the gas was returning back to the tank and that is the reason why my car has a cold winter start problem. suggested that i replace the gas pump for about $5K (freaking crazy because the car is probably only worth that much). my cold start problem only happens during cold winter days in the morning. the other 3 seasons, my car runs perfect and i can leave the car sitting in a garage for weeks and it will fire up right away. for now, i have been adding fuel cleaner into the tank every 6-8 weeks and it seems to help the winter cold starts (once the car starts up in the morning, it will run fine).

BTW, I am not 100% sure if the fuel pump is the problem because during the other 3 seasons, the car run perfect. I can even let the car sit for over 2 weeks and it will fire right up on the 1st. attempt. The only problem I have is when I start up the first time in the morning only during the cold winter months, and the car will run perfect for the rest of the day. One thing about the dealer, they didn't want any opinion from me and said they will figure it out. yeah right, even when they said to replace the fuel filter, there is no guarantee. Sounds like they just want to take one step at a time and move on to the next part. I am still wondering if there are any updates to the CPS s/w (the dealer told me "no") or whether they even checked. In any case, I don't have a problem for another 4+ months.