99 E300 occasionally won't start - PeachParts Mercedes-Benz Forum

shertex · #1 07-14-2014, 08:51 PM

My son informs me that the 99 E300 we just picked up on every once in a great while won't start (i.e. he turns key to start position and nothing happens at all)....I think it's happened twice. He then tries again and the car starts fine. It happens infrequently enough that I doubt our mechanic would be able to replicate the issue.

Does that sound like a starter in the early stages of failure? Something else?

tjts1 · #2 07-14-2014, 08:55 PM

Does he get no glow plug light or no turning over? I had this happen intermittently on the 97 prior to the glow plug relay failing completely

shertex · #3 07-14-2014, 08:59 PM

Quote:

Originally Posted by tjts1

Does he get no glow plug light or no turning over? I had this happen intermittently on the 97 prior to the glow plug relay failing completely

Just no turning over....glow system appears to function fine.

jay_bob · #4 07-14-2014, 09:04 PM

I have experienced that occasionally as well. Glow, turn, release, nothing. Try again, it starts fine.

I have a suspicion it is the start control relay that is part of the K40 assembly in the control box.

It may be an innocent thing, since it works like an old school clothes dryer start button.
The way that works is the button energizes the motor. A switch in the motor senses the motor is spinning and closes in parallel with the button. When you let go of the button, the motor switch keeps the motor running.

Just like if you tease the button on a dryer, the motor runs for a split second but does not keep running since you did not give the motor a chance to get up to speed enough to close the hold in switch.

The same thing can happen on the 210.

It uses the crank sensor and the engine controller to hold the starter motor on until it senses the surge in rpm when the engine fires. If you are too quick on the key you can remove the start command before the CPS gets a chance to confirm rotation and tell the start relay in the K40 to take over.

jay_bob · #5 07-14-2014, 09:14 PM

I also get in the 124 and try to bump the key to start it. Of course that does not work. I get spoiled with the 210 and the 164 that have the auto start feature.

shertex · #6 07-14-2014, 10:00 PM

Jay, am I to gather that your 98 has been doing this for some time and has not gotten worse?

shertex · #7 07-14-2014, 10:22 PM

Reading some posts I wonder if replacing the K40 module just makes good sense after a while.

jay_bob · #8 07-14-2014, 11:22 PM

Correct, I have had this happen maybe a half dozen times in the last year and a half. It does not seem to be increasing or getting worse, it seems to be operator error whenever it happens.

Replacing the K40 proactively is not a bad thing to do. It is one of those electrical things that will render the car useless if it fails. However it is one of those things that can be easily replaced in the field with only a Philips head and your fingers.

I think someone else on the forum with a W210 opened his failed K40 up and cleaned up the solder joints and brought it back to life. So if you don't want to spend the money on a new K40 that may be something to check.

jake12tech · #9 07-14-2014, 11:53 PM

Quote:

Originally Posted by jay_bob

Correct, I have had this happen maybe a half dozen times in the last year and a half. It does not seem to be increasing or getting worse, it seems to be operator error whenever it happens.

Replacing the K40 proactively is not a bad thing to do. It is one of those electrical things that will render the car useless if it fails. However it is one of those things that can be easily replaced in the field with only a Philips head and your fingers.

I think someone else on the forum with a W210 opened his failed K40 up and cleaned up the solder joints and brought it back to life. So if you don't want to spend the money on a new K40 that may be something to check.

That would have been Dr. Bert IIRC. He isn't much active these days, but you can find his post pertaining the subject.

shertex · #10 07-15-2014, 05:56 AM

Interestingly, one of the things I learned about from the PO was the feature where you don't have to hold the key in the far CW position to start....it will "catch" with just a quick turn. Yet it also sounds like this creates higher risk of the ignition doing nothing.

TMAllison · #11 07-15-2014, 12:06 PM

Use the auto start feature and let the computer take over. Its what its for.

I'd guess you have a dodgy K40 relay. When it gets worse, the engine will crank, but the SOV won't open. May get worse this Fall as the weather cools off and expansion/contraction of the cracks on the circuit board become greater.

Could swap K40's since you have two and see if the problem moves to the 2nd car......pull the battery cable first.