WienerWater

I read another post about the crank position sensor, and makes me wonder what is up with mine now. About 2 weeks ago, wife called and had started the ML, drove about 3 blocks, went in to buy some groceries, and when she went to leave, it would only turn over, and not fire/start. She tried 5-6 times, and nothing. I came down after it sat for about 15 minutes, put in my key and away it went. Ran great since. Now today, I started it, drove it around the block to my front driveway, shut it off and about 20 minutes later, it was dead, same as before. Tried several times, let it sit for 15 minutes, and away it started. I left it idle and after about 5-8 minutes, it just stopped and nothing again for 3-4 tries, let it sit 15 minutes, and away it went. Drove it around the back to my shop and Mercedes mechanic was giving suggestions over the phone. I am the second owner, all records up to date when I got it last August, and he (original dealership) figured the plugs were due, since it has 90,000km (55,000 miles), I pulled the (I think original Bosch) plugs, and the platinum tip was totally gone on all of them! Changed them out with NGK and starts fine 10 times, drove it around some. Could this be MY issue, or is the CPS still suspect to all this?
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ML God

Sounds like a CPS going out...very easy to change on a 320......little trickier on a 430

WienerWater

Will maybe order one in.Are these the common symptoms, works today, then maybe dies, then comes back again? I can't see the plugs causing this erratic behaviour is all, either they die slow, but not intermittent starting issues.

ML God

Yes very common....something else is might be...very rare is i am finding a lot of sub harness to the fuel pump burning up (melting) for what ever reason the fuel pump is pulling to much current and melting the wires. but more than likly it is a CPS

WienerWater

Ok, new CPS is on the way. I asked the shop manager, who has been trying to help about this CPS, and he said he hasn't done one in about 2 years. But, I am thinking most of the '99 ML's were probably leased, and because it is in a smaller center, maybe he only sold 10 that year, and 1-3 failed.
But then again, he might be a manager, and not a smart mechanic.
I will try and pull and OBD2 code as well, see if anything was stored. Not sure if that will come up or not.
Thanks again for the input!

WienerWater

Just an update.....I used my OBD2, and pulled no stored codes...nothing. Not sure if this CPS type of problem would leave a code or not, but so far, the plugs are the only thing I've changed, and no problem yet. Will change the CPS anyway, and update if it happens again.

ML God

It dosent always store a code...

WienerWater

I am also told that it could be the fuel pump, but not so sure it would react this way. I was thinking the pump would die, either intermitent, but constant , say every 20 minutes when it heats up, or just die completely. What symptoms does a bad pump usually have?

WienerWater

Well, the proper CPS arrived this morning, put it in, and has ran great all day. Nice hot weather, made about 10 starts, no more problem.
Read quite a few posts of guys going to dealers, and the shops changing everything from fuel pumps, filters, lines, modules...you name it, just to find the CPS is shot. Even the dealer I bought mine at, first thing he wanted to sell me was some ring inside the ignition for the anti-theft system,along with maybe a fuel pump, lines, etc.
This is really a simple/obvious and cheap fix and I am surprised the dealers are so ignorant to the real problem.
Thanks again.

ML God

Not all dealers are ignorant!!!!! Please dont make that assumption

WienerWater

Not assuming ALL are ignorant, but it seems so common a problem when you start reading, and what people have spent to get it fixed, is pretty sad.
My problem was solved immediately, just from reading the forums.
Anyway, I'm happy and hope others read a litle more often as well..
Thanks again for your input and help.

Cali_ML

How much is it to replace the CPS and where is it located?

Cali_ML

I have a 99 Ml320 with a bad CPS . I have been looking for the CPS unit for over an hour and still can not find it. I have also look at other posts on this site. Can somebody help me take a picture of or tell me where it is located.

Thanks,

WienerWater

It's pretty tough to get a picture of it because of the location. Best thing is to open the hood, and using a bright flashlight, view from the drivers side close to the master cylinder, looking towards the the back of the engine where the transmission connects to the block. It is just down the side a bit from center (drivers side). Maybe try using a mechanics mirror if you still can't see it. There is a simple black connector that pulls straight up when released, and a small torx bolt holding it in place. I found it easier to feel around (gently) down there to find it rather than just to get a good veiw of it.

00ML430 Bulldog

Is this it?? They call it a reference sensor. when you open the link there are two items. you can click on the bottom one to see a picture. You might have to call the verify which one is for your truck CPS??

WienerWater

I checked the link, and the second one down shows a picture of 2 sensors(they are crank sensors, just a new name maybe?). The one on the left is the one I used. I see the part #'s they are using don't correspond to the MB/Bosch unit, but looks the same. Best thing to do, if you have the time, is pull out yours, get the # off the side, and order the same one. I know they updated the part #, but is only 1 digit higher than the old version.
In my case, the dealer sent me one he said applied to my V.I.N, but sent the wrong one, so pulled mine and ordered what I originally had in there.

Cali_ML

Found it, but now how do you remove the tiny little bolt ? What size socket do it need to use ?

Thanks

ML God

The socket you use is an E8 inverted torx. After you loosen it DO NOT DROP AND LOOSE THE BOLT. It takes some finesse but be patient