Engine isn't starting right...
 

2005 C240 4Matic (M112 engine) 25k miles

The car is still under warranty, but the dealership is brain dead, so I like to diagnose problems before bringing the car to them.

When starting the engine it feels / sounds as if it is not firing on all cylinders for the first 3 or so seconds after it starts. After that it runs perfectly. No check engine light. What's weird is that I only have this problem if the car has been sitting for 24 hours or more. The longer it's been sitting the worse. Started about 6 months ago and has been slowly getting worse.

I'm thinking it's gotta be some kind of initial fuel delivery problem. Or maybe my (original) battery is going? The starter seems to have plenty of power though...

Anyone have this problem?

could be your throttle body:

https://mbworld.org/forums/c-class-w...-cold-cel.html

I have begun to notice my car doing this recently. Also, only after it sits a long period of time. It's a hard thing to describe. Mine doesn't last 3 seconds, more like 1 second, but it feels like the car's first two engine turnovers are strong but the final one results in a weak start almost. I put my car in dyno mode to check the voltage of the battery. I've chalked it up to the battery. Until it fails to start, I'm leaving it be. Wish I could be more help but you're not alone despite us having two entirely different engines.

This sounds exactly like my problem. Maybe I'm stretching it a bit by saying 3 seconds. If it were any other car I would swap batteries with my other car just to check, but I don't want to fry the front or rear SAM....

Im having the same problem as well, i thought it normal since I was hitting 88k mi on the car. It gets worse when the car isnt driven for a day. The first few seconds, sounds like the engine is going to stall after being turned over, but doesnt. Now im assuming this isnt normal, what could be the real cause of this? (fuel delivery? battery?) can it harm my engine if this isnt fixed?

I have the m112 engine as well.

acr2001 - Does your car do a lot of short trips or in town driving? How often does it get a good long fully warmed up run? The car should start perfectly foot off the throttle & one quick flick of the key because these cars have a crank 'till they start program.

My car tends to be an in-town car where the plugs seldom run in the self cleaning range. I started suffering some spluttering starts & we changed plugs at the 45,000Km - 27,900 mile service & it's been perfect ever since.

You can't really clean these plugs. Put them in a plug grit blaster & they are destroyed. At your mileage I think it's plugs.

As Glyn said, I suppose it could be your plugs. My car is driven a lot of long-distance trips and has just 51k miles so I don't think so for me. The reason I think it is the battery is because I've had other cars do this. Starts get weaker as the battery does. I wish one of us could better describe it for someone like Glyn or mleskovar but the best I can do is say that it feels like two very strong turn-overs then a slight stumble as the engine starts.

Battery voltage on my car after sitting 12+ hours is 12.4v per dyno mode. It runs down to 10.1v during start-up.

It could be the battery but Benz batteries usually do a lot better than that. The C240 is so smooth & such a perfect starter usually that one becomes pernickety. When mine started it's nonsense I was being ultra critical. If I got someone else to start the car so I could put my hand over the exhaust, I could feel the momentary misfires & then it would clear & idle perfectly. Just needed to clear it's throat. It never threw a CEL, there were never enough misfires to do this. I know 27K is way early for long life plugs but the 100,000Km or 4 years depends on them running in ideal conditions. I kept my plugs - Next time I know I'm going to do a 1000 plus Km trip I will pop them back in & clean them that way.

Well my C230 is not so smooth. From how it sounds at cold start, you would have thought I had yanked a cord from under the hood rather than turned a smartkey in a Benz. But I love it anyway.

My car (2005 C230K M271 with 37,000 miles) has been doing the same thing recently when starting in the morning. It cranks maybe one or two cranks longer than usual and once it starts, it sputters and nearly stalls for the first second or two, but then idles fine afterwards. It's similar the older, non-fuel injected cars from the early 80's where if you didn't step on the gas a bit while starting, it would sputter or barely start at all. Not something you want to associate a Benz with.

Truth be told, I drive mostly very short distances (1 mile to work) every day. So I'm wondering, if like Glyn mentioned, it might be the plugs fouled up. Perhaps a good long, sustained high-speed drive will help out.

Cintoman

Yes Glyn, my car does 90% very short trips. I always use the "touch start" feature so I'm never holding the key. To be honest, I also drive it very hard often getting into the high RPM range. I'm stuck between plugs and battery. The funny thing about the battery is that charged, it reads 12.1 volts which seems slightly low. When starting it usually goes as low as 10 volts (for only a second of course). I tried turning on *all* accessories and then starting the car, engine still starts right up perfectly if it's been recently driven.

I guess I should get the battery load tested and otherwise pull a spark plug to see how it looks.

My car did it again this morning. I immediately shut it off, waited three seconds, and started it again - it was perfect. It will only do it at the first cold start. I use the touch-start feature as well. My car isn't cranking longer. It takes exactly 3 engine turn overs. First two are strong, the third turn over is weak and the engine stumbles slightly (very brief, probably .5 second) then runs fine. No codes. Voltage after sitting all night shows 12.2-12.4 volts, running down to 10 during start, and 14.2 during warm-up.

I have decided not to worry about it. But it would be interesting to know why it does it.

Edit: Need a definition of short trips. I drive 30,000 miles a year. To get anywhere from my house requires at least 15 miles. I usually drive about 60 miles a day.

LILBENZ - your service cycle should be more than enough to keep plugs clean. After all the crap we had with Phils car I think that the M271 is very sensitive to throttle body malfunctions. Not necessarily flutter like Phil had but even deposit build up. I think the TBs need to be kept spotlessly clean.

I postulate:

Could this possibly have something to do with the fuel delivery system? I'm going to experiment tomorrow. Instead of just sticking the key in and twisting, I'm going to let it sit for a few seconds in position 2 where the fuel pump pressurizes/primes. The fact it will only do this after sitting for a long time makes me wonder. This morning I shut it off immediately and still it started fine the second time.

"Battery Voltage and State of Charge:

12.68v . . . . . . . . . . 100%
12.45v . . . . . . . . . . 75%
12.24v . . . . . . . . . . 50%
12.06v . . . . . . . . . . 25%
11.89v . . . . . . . . . . 0%"

I've read other articles that say a fully charge battery = 12.7 volts. Lots of short trips are bad for the battery as well as the motor. After a drive of 20 miles or more check the battery voltage. Then let it sit over night and test it again before starting. Should be close to 12.68 volts both times.

Odd that the difference between fully charged and completely dead is less than 1 volt. But then again, I'm no electrician (or even close).

So mine varies between 75% and 50%.

You must do short trips. If not then you may have a drain or a weak battery. Assume that you would get a warning message if the charging was bad, but to check for sure - with the motor running you should get a minimum 13.5V across the battery. Check immediately after a long trip and if it's not 12.68/100% then something is wrong. If the voltage is OK and then it drops overnight then again something is wrong (bad battery or drain).

Actually my trips are never really that short. 15 miles at least. With the car running it is between 13.5-14.2v. Immediately after the car is shut off it is 12.5v. After sitting all night it is 12.3-12.4v. Seems like normal behavior for a battery that is 4 years old, no?

Car running - my 5 year old battery shows 14.1 - never bothered to check the rest because everything works fine.

You should always wait for the pump to reach rail pressure. It does this quickly. Listen - it's under the rear seat behind you. Take key to ignition position & you will hear the pump start & stop when it hits pressure. Some of us like Chris Brown & I are sensitive to the pump noise. Others don't even hear it.

Kinda low but if it starts and runs OK then it's enough. I'm not sure how long a trip (and with what accessories on) it takes to reach full charge. My last battery charged up to 100% and only dropped .1 volts overnight after 5 1/2 years until it finally died.

My battery always winds up back at 12.1 even after long trips. Alternator seems to be working fine, if I drive it w/ the engineering menu on I can see when it is charging (around 14.5 volts max) and then it slowly ramps down once the battery appears to be charged. After turning the car off my battery is just under 12.7, but it begins to drop within minutes. I'm thinking its shot. I had a feeling it was going over the winter, and it was a bit low on fluid. Topped it off, but that didn't seem to help.

If I turn all the accessories on with the engine off the battery will get below 12 volts within 5 minutes (but still starts the car OK).

If the battery starts the car OK I doubt it is causing this slight stumble.

True....people were questioning the battery health and I was offering ways to check it out. Running the motor takes much less battery than starting the car. If you can bump start a car with a dead battery it will run (I wonder if you could do that with the EIS system?).

Off topic - see you on screen. mleskovar - Are Benz paint colours international? I see you recommend these pens & they look like a really good idea. My colour is MB 0744 which is known as Iridium Silver in South Africa but I see is called Brilliant Silver in the US under the same code. Do you think 744 is the same colour worldwide never mind what they call the colour in a specific market?

My car is also 744. :p:

I did another test today. My battery showed 14.2v with the car running. Immediately after shut-off it said 13.0. Less than 1 minute later it showed 12.7. I stopped watching at this point. I'll look again later. So you don't think this would cause the issue? The reason why I thought so is because it feels like (in my car anyway) a weaker cold start than it used to be. I'm not worried about it, though. It runs fine.