buckingbrutus

Read through many threads and am still scratching my head, so apologies if this has come up before.

Engine will crank, and hit for a split second, then die. Rear trunk was not opening by key or button, but not sure if other issues are there. I posted a video to YouTube of the no start condition...any advice?


Battery was dying, and I jumpstarted several times with no issues. Hooked up battery charger overnight (1st time) and car would not start. Tried to jump again, same no start. This was all cold morning; Later one day my wife was able to start the car when it warmed up. I replaced battery, and same no start condition.

C230 Sport Coup

1. Check the voltage. Under 12v?
2. How old is the battery? Really Old? replace it. Mercede's operates like the human body, shutting down power to
non-essential systems, when it see the battery is on it's last leg, like the radio, climate control and perhaps the trunk selenoid.
3. Clean the contacts. Check the battery cables, did they leach battery crud into them?
4. Is all the above good? Starting when it's warm possibly points the starter itself.
a. Locate the starter. Find a long piece of pipe or metall rod and carefully fish it in and around the various wires on top of the starter.
b. Lift the pipe up and down, careful to not catch any wires or hoses, while firmly banging the starter with the pipe. Try to start it. Repeat a few times.
c. if it starts it's the starter. Either pay someone to replace it, or DIY. DIY is a PIA only
because you need like a 3-4 ft extention and fish the socket to the bolts on the back of the starter, in front of the tranny.
While actually operating the wrench from the back of the trans tunnel. Easiest if you have access to a lift.

Take to an auto electric shop. Have it cleaned and replace the brushes. $25 and you'll be back on the road.

buckingbrutus

Thanks for the Reply

I replaced the battery last week, and it did not change anything. Old battery was around 9V, new one is 12.54, but to no avail. All contacts were very clean, and I've never had a problem with cranking (at least with a good battery or Jump).

It might be hard to hear in the video, turn the volume up, but you can hear the engine does ignite for a split second, and it revs up to around 2K, then shuts down. I don't have an adapter for the fuel line, but I opened the schraeder while cranking and there is plenty of fuel pressure.

I did unplug the Crank Position Sensor on the back, and when I plugged it back in it fired up. Next morning it would not fire off, so I ordered a new CPS and will see how that does. Also checked fuses just because and did not see any blown.

I went through a bunch of systems, and seems like everything is now working fine, so I don't think the SAM was affected.

Still doesn't make sense...From reading, it sounds like a CPS failure will cause it to crank and crank without ever firing, or just run erratic, it's weird that the ignition will hit for a second then shut off. I've had other cars with CPS problems and never heard of something like this caused by a CPS. Either way I'll update with what I find

neurodave

My CPS was causing intermittent no-start situations over the summer. Heat played a great role in those. If the engine was cold, it would start fine 9/10 times. However, even after replacing it, I've had a few no-start moments. I blame that on myself for replacing it with a cheap Advance Auto part. Now that it's winter, I haven't had any issues, but I'll be replacing it soon for a Bosch unit.

Good luck!

buckingbrutus

Update: Replaced CPS yesterday (Bosch). Car started before doing any work to it, but ran rough. Replaced CPS, and it ran good.

Old CPS read 750-800 Ohms
New CPS read 1000-1050 Ohms

Thought that fixed it, but nope...did not start again this morning. It was colder, around 45°F. It seems to start above ~60°F, but not below.

Just for more history, I have previously seen a P0170 code, so I cleaned MAF and throttle body and car ran much better, but still just slightly rich (although I did get 26-27 MPG on county roads). Was able to drive around a couple days (when it was warmer), but battery died and was not able to hook up OBD. Replaced battery and cold start problems began (unsure if any coincidence at this point)

Glyn M Ruck

Check the fuel pressure at the Schrader valve on the front fuel rail. s/b > 3.8 bar or 55 psi while cranking.

buckingbrutus

Another update: car will now sometimes start up fine when cold (this morning ~34°F). Got P0100 code the other day when driving around for lunch, cleared it this morning and it came right back up (no other codes), MPG is a little low.

Previously, I had unplugged the MAF, and the RPMs immediately began to surge up and down and when I pressed the throttle the engine died. I've heard unplugging the MAF should smooth out to a default map, if MAF is the problem, so does this indicate something else?

Some symptoms lead to MAF problem, so I will try to clean that and Throttle body again.

amcink

it seems that is having problem to start on cold - I would look into changing the coolant temperature sensor?

buckingbrutus

Not sure if it's coolant sensor; Took some readings this morning:

Sensor:---------KOEO--------KOER Cold-------KOER Warm
MFD Temp------39F----------39F---------------42F
IAT Temp-------50F----------50F---------------72F
ECT Temp------46F-----------50F---------------150F
MAF (g/s)-------0-------------9.7---------------4.6 (3.5 at idle once I got to work)

I know MFD and IAT/ECT are a little off, it was about 36-38F outside, but I think that's accurate. The MAF concerns me, I've heard it should read around 3.5-4 at idle, and the fact that it reads from 9.7 to 4.6 to 3.5 (all at idle, just various levels of warmth). I'll plan to clean the MAF and TB again this weekend (more thoroughly) and see if that makes a difference. I presume this is why I'm still getting the P0100 code

Yesterday morning I had to goose the throttle some to just get the engine to idle, after ~ 30 seconds of that it idled on its own

buckingbrutus

Bump

Finally got a gauge on the fuel pressure, was ~56 psi. Now it won't start at all, even when outside temperatures are ~60-70°F

If I unplug the MAF, what is supposed to happen? Previously when I unplugged it, the engine would surge all over the place (but I think I had the key on when I unplugged it, not sure if that matters?)

buckingbrutus

Unplugged MAF again yesterday and engine finally started...new Bosch MAF on the way

While I was poking around, with the ignition on, I could hear a whining/buzzing noise coming from the throttle body. I can post a video if that helps, but is this supposed to happen?

buckingbrutus

Just to update; New MAF fixed the problem, and the car has power <1500 RPM now!

I inherited these problems, so it's nice to have the power the car was meant to have.