Hey Scotty, I gotta 2000 Mercedes SLK230 with 175,000 miles. I have been daily driving the car for two years now, but something unusual happened today. I drove the car one morning for about 15 mins. I parked it outside my house and shut off the engine. About five mins later I got back in my car and tried to start it, but the car would not even crank. Only accessory lights came on. My battery is two years old so I tried to attach a jumper. I turned the key and no crank. After a few minutes the car started fine, and ran. I even shut the car off again shortly after and cranked it again, it started fine. I decided to put a volt meter on the battery, but I am getting 12.7 volts, which is still good I guess. Also no trouble codes in the car.
I am wondering if it was even the battery because when the jumper cables were on it still did not crank for about 1-2 minutes. The car was on operating temperature at the time and it was about 97 degrees outside. It was pretty hot that day. I decided to park the car for a couple hours and try turning it on again. This time the car was a bit cooler. It started fine. Then I decided to turn off the car wait another couple hours, this time I turned on the car and waited it to go into operating temperature. Once It got to operating tempt, I shut it off, waited a few minutes, and tried to start the car. This time it fired right up perfectly fine.
Now I am trying to figure out what caused it to not start in the first place?
This situation did happen about 2 years ago when I first purchased the car. I was getting gas and after filling up I tried to start the car. It was a hot day and the car was warm. I turned the key and no crank, just accessories on. The battery had just been replaced, but not knowing what to do, I put a jumper cable on the battery and then it started, but at the time I was skeptical if the jumper did anything since the battery was still new. It could've been the car decided to start and I happen to put the cables on the battery terminals. This was the only other time a no crank no start occurred when trying to start the car warm after only a few minutes. Since then the past two years this situation did not happen until recently.
I have replace the spark plugs, coils, crank shaft position sensor, alternator and cleaned the maf and throttle using the spray cleaner.
Scotty, I am wondering what would cause a car to start fine when it is cold, but suddenly not want to start when warm? This has only happened twice since owning the car for two years. I try to duplicate the problem, but cannot seem to do it consistently. I am hoping that it is the battery, but I am not sure. Other than that it runs good. It has been my daily for two years now. Thanks!
I have replace the spark plugs, coils, crank shaft position sensor, alternator and cleaned the maf and throttle using the spray cleaner.
None of those things would prevent the starter from cranking the engine.
I would suspect the decades-old starter or ignition switch. If and when it happens again try hot-wiring the starter solenoid to see if the starter itself works. Alternatively hit the starter with a 2x4 or a dead-blow hammer. That will frequently cause a bad starter to temporarily start working again.
The fuel pump , fuel tank pressure sensor/switch and wiring are kinda known to cause these issues with starting after heat soak. I can't remember off hand if your exact year is intergraded or not but I would start with that.
Wanted to give an update. I went away for about a week so the car sat until then. First day back I went to start the car, no crank. Put a volt meter on the battery, this time is was read only half full. I assumed it was battery, because a jump start helped it start again. Decided to replace the battery. Started up fine and worked with no issues starting for a day. The next day, I go to the gas station with my car, turn off my car, after filling up my car has a no crank situation again. Just accessory lights on, engine does not turn over. After about 5-10mins it finally decided to start. Engine was off and warm again when this happened. I decided to bring it to my mechanic. Unfortunately when I arrived at the shop I tried to duplicate the situation from earlier, but was unable to do so. The car just decides to act normal now. I will leave it for them for a bit, hopefully the car decides to not crank while its there. My mechanic says it could be the starter or even the key and ignition itself. Also the car has no codes and the car runs fine when its on. I explained to them my exact scenario so hopefully they can duplicate it.
Here is an update on the SLK. Quite a bit has happened since then. First mechanic was unable to duplicate my problem. Car would run normally at the shop and turn on every time. I take the car back, runs fine and even starts fine. After a few days on my way to work my car stalls on the freeway and I am unable to start it until waiting for about 20 mins. Car has a no crank no start situation.
I was able to get info on a Mercedes forum about common faults on my car. Apparently if you get a no crank no start situation on an SLK, the most common is replacing this K40 relay. It is basically this PCM by the ECU. It costs about 200$ at the dealer and they tend to go bad after about 18 years. The circuit board on the PCM gets hot and starts losing connection. You will get funny no starts and engine problems, but they will start as intermittent at first. This is why it only happens when warm because when the car is cold it is fine, but as it heats up issues can occur.
Also specifically on the SLK if you get a no crank, but the engine fan is running, it is a very high chance it is the K40 board going bad. Anyways, I put in a new K40, literally takes like 10 mins to remove, basically just plug n play the new one. I have been driving the last five days no issues what so ever. In fact the engine is running even better than ever. Apparently the old k40 was causing me to lose some performance even with no check engine lights.
Just wanted to put this out there. This is specifically an SLK problem as the car gets old. Parts such as the k40 relay just wear out and need replacing. Since replacing it, car runs like a top again and no more starting issues. Thanks for the help everyone!
I'm really sorry I didn't get back sooner, I've been really busy and completely forgot to check back. Crank no starts with Mercedes for the most part is usually a relay. Depending on what model it can be the fuel pump or starter relay/fuse those are the main two things to check out. My sisters CTS had a issue with PCM, it had a little moisture on the board , corroding and shorted out. That is a issue in her year but didn't know that was a problem in the slk
How is the car now? Did you get her up and running yet?
No worries, yes, basically all first gen SLKs need to have the PCM replaced every 20 years. It's basically a gigantic fuse located near the ECU. Takes like 5 mins to change out. Only thing, it's 200$ at the dealer, but if it lasts 18-20 years, it's worth it. Basically the solder on the circuit board goes bad over time which causes the communication to the ECU to fail. The main symptom is a no crank with the engine fan running. I found that out on an SLK forum. I changed the PCM three weeks ago, car hasn't had any problems since. Been daily driving my car every day to work.