Hi Guys,

Does the CPS affect cold and warm starts? I had an issue with my o2 sensor that got changed recently and we noticed that the vacuum lines around the MAP sensor are cracked a bit. So I got a new MAP and new lines, I didn't change all the vacuum lines only 3 on front of the engine that I could reach, including the hose for the MAP. Now when I finished my car started like 5-6 times on the first key with no issue. I went for a drive and when the engine got nice and warm it didn't want to start anymore on the first key. I'm wondering does the heat and the CPS have anything to do with this problem?

 

Thought I would bump this thread with my own recent experience. Car is an 83k mile c240 wagon/daily/trash/box/hauler. First incident happened about 3 weeks ago or so, no start, all the symptoms spoken of in this thread. Did not re-occur for another 2 weeks of regular driving in hot to extremely hot weather. Popped up again last week, and I scanned the code, bought all the parts I needed and was ready to go. Happened again yesterday afternoon, dropping off the recycling, and I was kicking myself because I knew I probably shouldn't risk it. Took almost 45 mins to get it cooled down enough to start again, a significant increase over the previous two times.....so clearly getting worse or at least not better. Finally dove into the project this afternoon.

First off, this thread and others were very helpful in terms of getting an idea of what I needed to do, and what tools and part to buy. I'd also recommend this video for anyone not familiar with the underpinnings of a w203 engine bay. That being said, it was really really easy......like 15 mins of work, expanded into 30 because I am **** about taping connectors and hoses off while I go. Here is a quick rundown:

1. Tools - Things you absolutely need = E8 Torx Socket/female and a good flashlight. Things you probably want = 1/4" drive ratchet and a few extensions of various sizes. I did it with a 3", 6" and a swivel joint. You DONT need a mirror, e10 torx (I bought a 3/8 inch drive torx kit which I kept in case I have to do the throttle body one day), or really anything else. So E8 torx socket, flashlight, and some 1/4" drive stuff most people already have.

2. Part - same as already mentioned.......I bought mine from Oreillys because the girl who works there is cute, and MB wants like 3 times as much.

3. The work itself.......you don't need anything more than a ****ty towel to put down on the front part of the motor, where your waist/stomach will be laying.

Tip 1 - watch the video I posted, and removing the airbox and MAF will be less than 5 mins of your time. This is probably the longest portion of the job.

Tip 2 - Don't F with the MAF.......just take it out and put it back in. Maybe one day you want to go back in there and give it a good cleaning, but just limit the variables for now. The tube that connects to the right side of the MAF accounted for the only injury I got during the entire evolution. It is a pain in the *** to remove, and goes back on very easily. Strange I know.

Tip 3 - Unless you have the arms and hands of an elf, you need to remove the MAF and intake assembly leading up to the throttle body. Once that is gone, it is really easy.

Tip 4 - Literally don't try to find the CPS visually. Even for a first time guy, you can do it by feel. Just familiarize yourself with what the connector looks like when you have removed it so you know you got the right one. Once the MAF is off, just below it and to the right (above the bellhousing assembly slightly off motor centerline) is a very easily seen connector with a few colored wires. That is not the CPS connector, but it is your first handhold. Once you have that in your left hand, move your free left hand fingers slightly down, and slightly to the right (assuming you are facing the windshield/front of car). You will feel a second connector, which IS the CPS. You will probably not be able to see it, even with fantastic flashlight illumination, unless you really bother with it. And stepping back, there is no need to lay on the motor, and don't overestimate how far down this is.......it's just barely below the things you can see with the MAF removed. I spent a good 5 mins looking waaaaay too deep into the trans tunnel before I realized where the thing actually should be. And then it was right there. Again, you will easily find it with your hand and not your eyes.

Tip 5 - Pull the connector and make sure it looks like the one in the previous pics. It is the one connector down there that is at like a 45 degree cant, vs a pure lateral left/right angle......so it is a bit different than its neighbor.

Tip 6 - Once the connector is pulled, feel around with your left hand for the bolt/screw. It will be on the lower side of the sensor assembly. Then take your 1/4" drive with extensions and the E8 and lower it down there with your right hand. Grab it with your left hand, and guide it onto the bolt. It will loosen very easily, and once it is, take the ratchet off, and probably all of the extensions other than the short one connected to the socket. Then just hand loosen with your right hand, and guard with the left hand to grab the bolt when it comes out. Once free, place the bolt somewhere safe and then pull the CPS.

Tip 7 - Put the short extension, socket and bolt into your left hand, secure the bolt with your left thumb, and work it around until you think you have it lined up with the hole. Before this is your one useful flashlight moment. From the upper right, just above and to the right of the cylinder head, you can probably get enough of the CPS into view to align the fairing with the screw hole. If not, it is like perpendicular with the driveshaft. I didn't have any trouble getting the bolt back in.....just went in first try. Hand tighten the thing until you know the screw is in the hole. Then, take the socket/extension back out with your left hand, put the other extension and ratchet back on, and then put it back down the other side of the cylinder head with your right hand and guide it back to the bolt with your left hand. Hand tighten, it becomes readily apparent when you have torqued it enough (even without an 8 lb-ft or whatever 1/4" drive torque wrench that nobody other than weirdos own).

Ok now the thing is in, so just reverse the directions, and you are done. Before putting the airbox back on, make sure all the hoses around the top of the motor are secure again.....I nearly detached a couple, so just double check.

Fire it up, drive it around and get the motor up to temp. I did the whole rev to 2500 rpm in 2 mins, then hold for 20 sec thing, but I have no idea if that matters. Once you drive it around and get up to temp, park it back in the driveway and let it sit for 5-10 mins. Retry a start. It should fire back up. I'd try to keep it hot with a few subsequent starts, extended idling, shutting down, waiting a few mins, then retry, all with A/C running. Just to tax the system and make sure that it is getting real hot and still cranking and starting just fine.

Hope that helps, and I am a few beers deep so please let me know if anything didn't make sense. Last step.....lay into some good beer and take a shower.

 

Engine was cranking but wouldn't fire. Just replaced the CKP sensor, fired up right away. Having an extendable mirror and flashlight was key to see and get an idea of parts. After doing everything for a couple hours I could replicate job all by feel :P.

Thank you to all those on this thread and MBWorld.

 

Just replaced CPS on my 2003 C320 and I'd like to add (or emphasize) one thing. Instead of E8 Torx socket I used a 1/4" socket. I have an E8 Torx socket and it just doesn't fit well. The 1/4" socket fit perfect. The bolt clearly has a torx fitting but for some reason it just didn't grab well with the E8 socket. It could be the angle.

 

I am very late to this forum but I have the same problem. I have searched and felt for the CPS but cannot locate it. Has anyone attempted or successfully replaced it from underneath?