mekantor

Hello,

Since the temperature has started dipping below 60F here in the mornings, I've had a hell of a time with a cold start. After 4-5 cranks it eventually it fires up, sometimes sluggishly, other times very smoothly. Warm starts have been completely normal.

I instantly thought CPS, and swapped it. Same thing. Swapped again, still same thing.

Each time the sensors are coming out covered in oil. I replaced the CPS a few years ago and don't remember it having wet oil on it.

I'm thinking that the constant slow seep from the rear of the motor has gotten worse enough that the cool oil doesn't leak down from the sensor as it did during warmer weather, and this is impeding the functionality of the CPS, in turn causing the bad starts. Strangely I don't see any more oil actually coming out from that area when I look under the car; perhaps its not gushing out, but just slightly worse than before and enough to cause this.

Have any of you experienced this type of failure before? Before I get into the big job of replacing these leaky parts, could anyone offer other alternatives on what could cause bad cold starts?

I've removed a few transmissions at home without a lift and don't want to do it again, especially in RWD where I can't get that area of the body up high, so this will probably be a shop job.

Thanks,
Mike

new55

i dont think it would be rear main issue if the cps is covered with oil,,, i would guess valve cover gaskets -- you may want to get a little mirror or inspection camera and look around, you may have other leaks also -- check your battery also

mekantor

Valve cover gaskets are clean, I change them whenever I notice any leak. Battery is strong, it cranks until a time-out each time.

The CPS is dry on the outside, at the harness and the bolt. The rest of it is covered in oil, you can only see it by removing it.

I was going to make a video of it this morning, but it started right up. This seems consistent with the theory though, because it sat for 2 days and the oil would've dripped down off the CPS. Or its just confirmation bias.

210lvr

Sounds like 1 of 2 issues.

1) does your car make a chirp or squeak during this start up? Does the tip start turn off when this squeak happens? If so try some anti seize applied to the flywheel teeth with a brush through the starter hole or the inspection cover.

2) check your cam position sensor. Right front from driver seat. Cam sensor will cause intermittent no start because it doesn’t know where tdc1 is so it sparks on the wrong phase. This causes it to start every few tries in between a bunch of no starts.

if neither works post pack. The first option is free so try that. Fixed many of them like this.

mekantor

Thanks for replying,

1) No chirp or squeak during starting
2) This motor doesn't have a cam position sensor, the cams aren't variable. There is a crankshaft position sensor and I discussed that as a proxy for what I suspect might be the primary issue. I replaced it a few times and it didn't help, each time it came out covered in oil.

The weather got warmer for a while. It is cooling down again so the issue has returned. I'll have some time during the holidays to do cold starts with Star Diagnostics connected, so perhaps I can catch it in the act and get something definitive.

tlambert

Please post when you find out what the issue is. I'm sure this will help someone out along the way.

210lvr

if this is a 113k it has a cam position sensor. Right front bank of cylinder head.

this[img]
http://cdn4.pelicanparts.com/techarticles/Mercedes-W211/59-FUEL-Camshaft_Position_Sensor_Replacement/images_med/pic01.jpg[/img]

210lvr

http://cdn4.pelicanparts.com/techart...arge/pic07.jpg

This engine does not use variable valve timing, it’s not used for that in this application.

StarvingArtist

I can follow your logic, but i don't think oil can shield the sensor from a magnetic pulse. Have you checked fuel pressure?

tompoeschel

Sounds like a fuel pressure problem to me. I took out my CPS not long ago and it had a fine oil residue on it that's normal.

mekantor

It progressively got worse and eventually would happen with a warm-ish motor, so I tossed out the oil on CPS idea because it barely made sense to begin with and then I just kept seeing contrary info.

Started thinking it might be fuel, especially since I didn't smell near the exhausts any after lots of cranking. Turned out that it was the fuel pump relay! I even had a spare relay of the same part number sitting around.

I always thought a relay would either work or not. Such temperature sensitivity was a surprise to me. I wonder how many other relays will start failing this way and give random outages in cold weather.

tlambert