jspbtown

So today I drove the car for 1 hour. Filled the tank from my regular place. let it sit for 1.5 hours and it fired right up. Drove it again for about 45 minutes. Parked it for 20 minutes...it fired right up. Letting it heat soak for about 2 hours and will try again.

Can someone tell me what the normal operating temp is? My gauge says 1 bar under 100C (gauge go 40-80-120C). My OBD2 scanner (which I have been leaving plugged in) has it going to about 216F when sitting at idle after driving it for a while. Normal cruising has it right around 200F

Rudeney

80C-90C is normal.

jspbtown

So 176-194F is normal? Hmmmm...I guess I am running a wee bit hot then. Maybe a new thermostat?

Rudeney

80C-90C is normal, but on a hot day, sitting in traffic at idle, you can see the temp climb a bit, but the fan should kick on and bring it down. If you are seeing it stay above 90C, at idle, check that the fan licks on. If you are seeing it above 90C while driving, especially when it's not terribly hot outside, you may have a problem which could be the thermostat, or a blocked radiator, or blocked coolant passageways.

jspbtown

When I look up thermostats on places like Pelican or autohauzAZ they show 100c thermostats.

jspbtown

Well I think we are at the end of our quest for a diagnosis. Drove the car for about 1 hour this morning. Parked it for about 10 minutes. Easy re-start. Then drove it two minutes. Easy restart. Then drove it 15 minutes and parked it for about 1 hour. Easy restart. Then drove it about 2 minutes and parked it for about 4 hours. Then easy restart. This all occurred from 11;00am to 5:00pm in about 85 degree weather.

THEN.....drove it 1 hour. Parked it for about 20 minutes and went to start it and no start. Jumped out. Popped the hood. Grabbed a rag and checked the shrader valve for fuel (yes...I know...not as good as a gauge) and there was plenty of high pressure fuel spray with the key in the "run" position. Put the front engine cover piece on and poured a bottle of cold water on the ecu….and....it started right up. Time from no start with hood open, through checking the shrader valve, to pouring water was maybe 5 minutes.

The drove the car about 45 minutes and let it sit for about 3 hours. Came out and tried to start.....no start. Poured 1/2 bottle of cold water on the ecu and it started right up. Time from no start to hood open and water on...about 1 minute.

I think I have an ecu problem. Any dissenters?

Anyone have any suggestions on the repair? I have done a shallow dive and see ecu rebuilders. New ecm through Mercedes is crazy money.

Fatz

There a lot of repair operations out there. Some of them may be limited to changing only the current drivers, which is probably the most common failing component. You might ask them their diagnostic capability (what kind of testing they do etc.), if you plan to have your unit repaired and returned to you. Some repairs/exchange operations send you a replacement unit and credit you for the defective (core) when they receive it.

I used CarComputerRepair (they are in Cary, NC) for my ecu. I wanted to retain the tune and not have it reflashed based on the VIN or to go to a stock replacement flashed per the VIN. It cost me $600. Someone else on the forum used a seller on ebay and seemed pleased with their service. The one I considered from ebay would refund your money if they could not repair it and they had a 2-3 day turnaround. And I think the cost was in the $300 range.

If my ecu was not tuned, I would have tried the no repair/no cost (except handling cost), and went with an exchange if no repair/no cost option did not work.

exhaustgases

I changed a crank sensor about 2 years ago a clk430, and it was purchased from Oreilly's, I'm sure way less costly than MB. Normally if is (it) that causing your no start the CEL will come on and a code will be set. If a person is going to trouble shoot with parts changing its just less costly doing something like the O reillys deal, and very likely the part is made the same place the MB one is.
So is that ECU located under the hood?

jspbtown

Fatz...thanks for the email. I checked out CarComputerRepair and am discussing it with them now. They do seem to have suffered from some poor reviews lately. The EBAY guy was Presser I think and I have sent an email to him. He has some good reviews.

exhaustgases...thank you as well. The MB part was about $20 more than the local parts store and it was in stock so I just went with that. And yes...the ECU is mounted on top of the engine and is visible through a cut out in the engine cover.

Rudeney

Just out of curiosity, have you tried disconnecting and cleaning the wiring harnesses on the ECU? Also, which doing that, remove the ECU from the engine and clean everything there very well - you may have a layer of dust on it.

jspbtown

Yes....I bought the CRC cleaner and thoroughly cleaned the ECU plugs and the pins in the ECU. I cleaned the top of the intake as well.

Pouring cool water on the ECU results in an instant ability to start.

Rudeney

OK, I think you have all the bases covered then and it's going to need some electronics expertise to fix. I will be very interested to see how this gets fixed and at what cost.

exhaustgases

I guess that explains a heat related problem, what were they thinking? There was a reason those things were never mounted under the hood in the past, heat is the main one.

jspbtown

Well I am combing through alternatives for an ECU. As you can imagine genuine MB is insane...especially with all the programming. I have sent 2 emails to Presser with no response. I have had a few emails with car computer exchange but their YELP reviews are terrifying. I have also had a few emails with Xemodex who have been responsive and have confidently suggested that a ground issue inside the ecu is causing my problem, See here:

https://xemodex.com/us/product/me9-7...-m273-engines/

Thoughts?

Rudeney

The ECU on almost all modern cars is mounted under the hood. They used to put them in various locations in the cabin, but then discovered that the length and paths of the wiring became a problem for RF interference and damage. Many makes put the ECU in a box under the hood (MBZ used to do this). Some have even put it inside the intake (upstream of the air filter) to keep it cool. The challenge is in locating is close to the engine so its wiring short and direct, yet keeping this critical part from overheating. With MBZ's modern engines (starting with the M272/M273 series), they put it on top of the intake manifold, encased in a heat sink. This is about the coolest place under the hood as the intake air is cool. Also, the shape of the engine cover is specifically designed to direct air from the engine suction fan under it and to the ECU.

And that brings up another thought for the OP: Check the engine cover, especially the front section, to make sure it's properly in place and also that the insulation on the underside of it is not "drooping" and blocking airflow.

jspbtown

The engine cover is in place correctly. I am 100% certain.

The insulation on the underside is slightly sagging off the hood but I placed a ball of tape on top of the ECU and closed the hood and it did not stick to the insulation nor did it compress so the insulation is several inches about the ecm.

Rudeney

That's good that the insulation on the hood is not contacting the ECU, but what about the insulation under the engine cover, specifically the front section of the engine cover. If you look at it, you will see that the cover protrudes a bit past all of the engine components. This is so that it will pick up air from the engine suction fan can channel it to the underside of the ECU. But if the insulation on the cover is sagging, it could block that airflow. This is just a "shot in the dark", but I'm just trying to make sure all your bases are covered before you go spending money on an ECU repair.

jspbtown

Ahh...got ya. I have had that piece off so many times and I haven't noticed anything....but I also haven't really paid attention either. I will do so.

A little update from today:
Drove 1 hour to work in 80 degrees. Parked it in a covered garage for 8 hours came out and it fired right up.
Drove home 1 hour in 90 degree heat and popped the hood and went inside for about 1 hour. Came out and it fired right up.
Drove about 15 minutes to the hardware store and shopped for about 10 minutes...came out and a no start. Pour 1/2 bottle of room temp water on ECU and it fired right up.
Drove 5 minutes down the street to the autoparts store. Shopped for 10 minutes. Came out and it reluctantly started and then stalled as I was backing it up. It immediately refired and drove fine. No CEL.
Drove about 45 minutes. Parked car with hood up. Came out about 3 hours later and it fired right up.

xsever

One hell of a goose chase I'll tell ya that! Very interested where this will lead. Good luck!

jspbtown

ECU was sent to Todd at Pressertech. EXCELLENT communication. I popped it out, overnighted it to him and he is shipping it back already. Cost was reasonable. Here is what he emailed me regarding my ecu:

"The board, likely, had some circuit damage caused likely by capacitor failing which caused the processor to get too hot.

Fatz

Hey, that's great news...…
BTW - you were correct in not choosing the CarComputer outfit...

jspbtown

New ECU from Pressertech was received today (via USPS overnight mail which took 3 days! I suppose they won't cover my extra rental day right?... ). Easy plug in and the car started right up and drove fine (other than some moans and groans for sitting for 5 days). Tomorrow will be the first challenge......does it start after driving 1 hour and sitting 2-3???

It damn well better!

Oh...and Todd over at Pressertech has been first rate. Since the USPS screwed up they are refunding the overnight shipping so Todd is handling that for me. Nice guy....if everything works its 5 stars.

Htxromero

I have a 2008 w211 I have long crank/Extended crank. I have replaced the following components.
fuel pump
sending unit
cam shaft sensors, crank shaft sensors
cam shaft magnets,
MAF sensor,
canister vent valve,
purge valve
spark plugs,
all 6 coil packs.
And I still haven’t solved the issue, I’m thinking it’s the starter. My battery is only a year old. I’ve also heard it could be the coolant temp sensor but mines seems to read fine. I have no check engine light. Car runs great and doesn’t stall.