DuncanMB

I have searched the forum but did not find a similar problem.
The car is a 2003 C230 Coupe 1.8l Kompressor.
From cold start the engine will crank fire up and then stall, restart on the second try, sometime just will not start at all.
The problem is not repeatable appears once in few days. When engine starts it runs normal - no CEL comes on even when the car does not start.
The crankcase sensor was replaced - no change in behaviour.
The repair shop says cam sensors are OK.
If someone had a similar problem or has some insights as what could cause this problem I would really appreciate your feedback.

Thank you

Glyn M Ruck

When you say the crankcase sensor - I presume you mean the crankshaft position sensor or CPS - your symptoms are typical of a wonky CPS

Utahkompressor

Similar problems! I have rough start in the morning, especially when the weather is cold. Sometime it didn't even start...just bumped up to 500rpm...shake shake shake...and shut down by itself...no CEL as well.

I asked this questions couple times, but nobody seems to have any experience with M271.

DuncanMB

I am sorry I replaced the crankshaft (CPS) sensor - no change.
The shop checked the camshaft sensors and they are OK.
I did try to clean the MAF again no change.
Is there any other sensors that would cause the engine to turn over but not start?

Glyn M Ruck

I hope you are not heading for this. A buggered cylinder head!



https://mbworld.org/forums/c-class-w203/267210-2005-c230-kompressor-coupe-consumption.html

Buellwinkle

The head problem on 2003 is just nasty misfires, not engine start issues. Where I would start next is to check fuel pressure, any shop can do it quick or buy a fuel pressure guage and screw it into the valve on the fuel rial. Look for about 40 psi at idle. Could be a weak or bad fuel pump or relay.

Next thing is bad coil packs. Doesn't say where you are from (update your profile), but when it starts getting wet and cold, minor cracks in your coil packs allow moisture to creep in and keeps it from starting some days vs. others when it's drier/warmer.

Even if CEL is not on, you can check for codes as codes that don't reach a threshold can still be found as pending codes.

DuncanMB

Thank you for suggestions - I am in Toronto, will update the profile.
I shall ask the shop to check the fuel pressure at idle. Is there a pressure regulator to maintain the rail pressure when engine is switched off?
Also another shop had a car with similar problem and the solution was SAM???
I though that SAM is to look after locking doors etc.
Is there any info available on SAM functions?


Thank you
P.S Last week was nice and warm and the car started every time first try.

DuncanMB

P.S. The only stored code that came up (no CEL) while car was not starting was related to MAF.
The shop did not want to replace is and find that the problem is not resolved.
They have found a replacement MAF for $350 and replacement SAM for $300.
I guess if the problem comes back it will be a "hit and miss" type of repair!!

Glyn M Ruck

The MAF is easy to check - just unplug it and drive on a default map for a while & see what happens

Glyn M Ruck

It does maintain rail pressure for a while. But when you start after the car has stood overnight you can always hear the pump start - get the pressure up to setting & then stop again so the system is ready for you to crank the car

DuncanMB

After overnight I do hear the fuel pump noise - will disconnecting the MAF not a create CEL?
If so do I just clear it with my scanner?

Thx

Glyn M Ruck

+1 Yes If it throws a code just cancel it. This is a common proceedure to check a MAF. If it is the MAF get some MAF cleaner and clean it properly.

Also, listen to Buell - Check coil packs etc. You should get misfire codes.

DuncanMB

Update - the car started Ok for last 2 weeks - this AM (weather at freezing and car was not used yesterday)it wwould crank but not start again.
Tried it twice - no start. Disconnected the MAF car started after car started I have reconnected MAF (with engine running).
No CEL was generated and car restarted after this 3 times during the day on first try.
Should I remove the MAF and give a good cleaning as the next step?

Thank you all

Glyn M Ruck

Sorry for delay - Just off the plane from wonderful Thailand.

You might be generating codes but would get an OBDII/CAN reader to check. Either buy or borrow. Cheap ones are only about $70 from Kragens or similar. Many places will put them out on loan for a deposit.

Yes, clean the MAF - it is significant that the car starts on a default map with it disconnected. Don't buy a new MAF until you have cleaned & downloaded codes. The MAF is suspect but might be a red herring.

Sorry - I see above you have a scanner - Do you get any codes?

DuncanMB

Hope you had a great time in Thailand.
No codes - the car ended at the dealer two days ago (second tow!!) - the diagnosis is defective fuel pumps (yes plural) - when car left out in the cold pumps not working when inside the shop all OK??
Cost $1000+, I am really doubtful since on at least one occasion the car was in heated place for 6 hours and did not start.
It is supposed to be ready Monday. I have to find out what is the policy if this turns out not to be the cause.

Glyn M Ruck

Thailand was a blast - I have some very fine Thai friends. Damn - so it was a fuel pump - we hope - had a 280E & this was the problem but it was not intermittent - one day it just would not start. Fuel pumps run flooded and slowly magnetic debris builds up on the magnets until they seize so I guess temperature could effect this. I had no idea that your car had dual fuel pumps. I've learned something. Do you know where the second pump is in the fuel system? The primary pump is between the fuel tank and the filter at the rear. I ask this question because I don't understand why both should fail if they are in series with one another - I would expect the primary pump to fail. I have opened a number of these pumps to check why they fail. Always the same reason. Rust particles stuck on the magnets. Infortunately you have to destroy them to open them or a clean up would suffice. They are crimped together.

DuncanMB

Nice to have good friends in the right place (Thailand).
Went to the dealership today and spoke to the SA. From what I gather this arrangement is more complicated than a commercial jet.
There are two senders and two pumps (access under the rear passenger and driver side seat. Apparently there is a equalization scheme - computer controlled to keep the two sides balanced. I believe the function is controlled by the rear SAM?
They kept the car outside and when it did not start they supplied the power directly to the pump to confirm it was not operating.
Next step is to install new pumps leave the car out and see what happens(Monday)- they feel that this 110% the cause of the problem..
I am also doubtful both are defective - they maybe replacing one as a precaution??
I wish some more info was available - the closest I could find is here:
http://www.installuniversity.com/mb/w203/w203/fp.html

Glyn M Ruck

OK - this is the same as my car - C240 - Two sender units - 1 with an integral pump, namely the LHS one, or in your case the drivers side.

So there are not two pumps - there are two senders and 1 pump. The pump is mounted in the left sender body. The pumps were separate in older Mercs.

Are you sure they say your car has 2 pumps? or two senders and one pump?

DuncanMB

The car is back - parts replaced:
1 203-470-23-94 Aux Pump
1 203-470-17-41 Sensor
We shall run it for a week or so before commenting further.
This was a very frustrating experience

Thanks for sticking with me

Glyn M Ruck

OK - this makes sense - sorry you had a hard & expensive time. I still wonder why they replace the sensor but maybe it's a belt & bracers approach because the sensors have a defined life & while you have everything exposed you may as well do it. Pleased you did not buy a new MAF - it was a red herring - The joys of the complexity of modern cars.

DuncanMB

Problem did not reappear for a week now - the dealer discounted the parts 75% (less than $200 for both)- since the extended warranty just expired but the bill was still over $1000 most of it in labour, largest being r&r for the two parts $200, test and reinstall rear SAM $100, full electrical test $200, fuel tank drain $70 etc.
Interestingly one of the items was a "control unit" software update.
In retrospect this would have been much easier to diagnose if it was not for a occasion when the car did not start in a heated shop.

Glyn M Ruck

Ah! well - that's really good news