johnand

+1. And what mileage were you at when it failed? I wasn't aware of a failure of the CPS on any M272 equipped C on the forum.

I noticed in EPC, there is a revised CPS part#, and it says in bold letters: DO NOT USE OLD PART. I am curious to see if mine is the older part.

pcy

I bought my '07 C280 in June '10 with 57K miles. The first problem I noticed after buying the car was that car would stall immediately after starting the car and some times it was taking a second or two longer time to start. On EPC, I saw the CPS was updated. Eventhough CPS was available on-line cheaper than the dealer, I went to MB dealer and got updated CPS for $51.75. I installed it. The car has been starting fine since then.

Once the MAF, and the elbow (that connects MAF and throttle body) are removed, and quickly learned to work with one hand (left hand) ... it wasn't bad.

While we're talking about CPS, since my '07 C280 is relatively new, the CPS came out without any problem. You should check out some of the folks on W163 having difficulty in removing CPS from 98 and 99 trucks. One guy broke the head part of the CPS leaving the stem part on the bell housing...

pcy

John, take a look at the picture below. The red line with arrows is your hand reaching for the CPS connector - AFTER removing the MAF and the elbow.

The bend in the red line I drew will be where you your left hand's elbow will be when you reach the CPS :-) Trans dip stick cap will be poking in to your hand.

d1no

Hey John did you get a chance to check your fuel pressure yet? My car is getting pretty annoying with this starting thing. Now it takes forever to start after its warmed up and starts on like 2-3 tries when its cold. Would this point to the CPS? Where is the CPS even located on the M271 engine. Can anyone check if the CPS part number has been updated for our engines?

johnand

Not yet. I plan on spending whatever amount of time it takes starting tomorrow morning to get it solved. I will post results tomorrow.

I'll check EPC for the part number for you car, and also WIS for the replacement directions when I get a chance.

johnand

Attached is the WIS document for replacing the CPS on the M271 engine. They list 2 part numbers for the CPS for the M271 engine. They are: A0031532728 and A0031532828. They appear interchangeable and the M271 does NOT have a revised part.

johnand

Attached is several documents for replacing the CPS for the M272 engine. You remove the air filter housing, MAF, air duct, then replace CPS, as PCY suggested earlier in this thread. Old part number A0041538728 MUST NO LONGER BE USED. New revised part number A6421530728 should be used. That part number will likely get you the interchangeable part number of A6429050000, which is the CPS used on most current MB engines.

LILBENZ230

I haven't read of any CPS failures on the M271 here, either. Seems uncommon. Mostly I see M112 cars with that failure. Maybe it's just age.

samaritrey

+1 on the age that will be interesting to see if it starts to be more common when the 06-07's get older and more miles.
BTW 154k with no cps failure since i have owned the car.
i really should not say that i bet it will fail overnight while my car is on the lift.

pcy

I also have a 98 ML320 (with M112 engine) with 170K miles, didn't have to change CPS. knock on wood.

d1no

I dont know I really doubt its the CPS on my car since it never fails to start, it just takes forever sometimes. My car also never turned off on the highway like many people described in the CPS thread. I really feel like its something fuel related for me. This whole problem started once the temperature dropped into the 30s and below. It cant be a bad fuel filter since it worked fine for few months.. I read somewhere where someone had a similar problem and it turned out to be leaking fuel injectors. How would I test that?

pcy

You can get a fuel pressure gauge, connect it to the valve at the end of the fuel rail. Then check pressure before starting and during starting.

mskembo

Was at a shop today out in the sticks (Longview, TX) that specializes in MB and BMW getting my oil changed. He made a suggestion that almost made my head explode. Check the battery output. As batteries start to get old they can loose some of their amperage resulting in the starter not turning the motor quite fast enough on cold days. He said most of the time this isn't recognizable to the ear, but put a new battery in there and bam.

Thoughts?

Glyn M Ruck

John acknowledges that these cars are voltage/power sensitive

LILBENZ230

mskembo - how quickly the starter motor turns seems pretty obvious to the ear, at least to me. I've heard slow, weak starts before. It sounds like mostly sound advice - that a battery that will operate accessories may not be capable of starting the engine.. but the part about you not being able to tell the difference sounds like BS. YMMV.

johnand

Man, was that ever a PITA. Got the CPS replaced. Just need to clean the MAF, and air duct and reinstall. You have to replace the sensor by feel, because you can't see it, laying on top of the engine. The bolt is a T27 Torx and not an E8 Torx, as was posted in other threads on CPS replacement. There is also a wire cable tied to the sensor, so you have to carefully cut that off by feel w/o cutting the wire. Not too hard to re cable tie it after the fact. I managed to not drop the bolt, so that was good. I did indeed have the older part number in there.

johnand

Replacing CPS = FAIL. Still no start. Hooked up fuel pressure gauge, and NO fuel pressure. I can hear the pump run, and STAR confirms it is activated, but no fuel pressure!

Off to find a pump.

d1no

Crap John that sucks, The cheapest oem fuel pump I found was on rockauto.com. Also on our w203s isnt there a special tool that you need to remove and install the fuel pump?

Glyn M Ruck

Damn - you are not having much luck. Probably good that you have the CPS behind you.

LILBENZ230

Do these cars have fuel shut off switches? If so, could it be that?

Weird that the fuel pump has died.. wonder if it was sourced from BMW?

Glyn M Ruck

No - Mercedes call them injectors

d1no

Also maybe it could be the fuel injectors? Other than that im not sure what else could be the problem. I hope a new fuel pump solves it for ya. Let us know how the install goes.

d1no

OK I need help with my car, this problem is still going on. Its probably anytime before Im stuck somewhere and car wont turn on. Could it really be my fuel pump like John's car?

I have not had a chance to get a fuel pressure tester but I tried to release some fuel where the fuel rail is you know how you do when your'e changing the fuel filter and nothing came out. Does that mean there is no fuel pressure? I can hear the fuel pump prime everytime I turn the key to position 2. I usually notice car can start better when I give it gas as it will turn off after starting even when warmed up. I am thinking its the fuel injectors. Should I just order new ones and if that doesn't fix it then its the fuel pump right?

pcy

IMHO, fuel pressure check must be done to rule out fuel pressure is reduced while the car is turned off and sitting there. I would do this before replacing any part.

d1no

I understand that but when I changed my fuel filter couple months ago, I unscrewed the cap on the relief valve thing under the engine cover and when I pressed it some gas came out. This means there was pressure right? Now when I did it today the car was warm I parked it and left it for like 20-30 min and when I came back the temp showed it was at 80c so still warm and car would crank and crank but not start. I checked the little valve under the cover and nothing at all came out so wouldnt this mean there is no pressure at all?