mhumphri3

Hi all, having some issues with my 2004 C240 sedan.

Occasionally we will experience a no-start issue. The key will get recognized, the radio, lights, and instrument panel will light up and work, but no cranking or starting will occur. If you wait 10 mins or so, it usually starts right up. This can occur cold AND hot. Sometimes it will occur after sitting, but we have also had it happen after my wife drives to the store, goes in, then comes back out 15-30 mins later to a car that wont start. Wait a few minutes and it starts right up.

So far we have tried the spare key, it doesn't fix the issue so I am assuming the issue is not the electronic ignition switch or the key. The battery IS as far as I can tell the stock battery from 2004 if I am reading the correct date on the negative terminal post? Can anyone confirm that the date is in fact located here on the battery?

Ive thought maybe a starter issue, but hoping it's just the battery. I just don't want to blindly go replacing parts if they aren't going to resolve the issue. Also, I have read about the starter fuse TSB and have confirmed that the 20A fuse is currently in place and not blown. Tomorrow I am going to pick up a battery terminal and cable cleaning tool and give that a shot. Could corrosion cause an intermittent issue though? Can relays slowly fail over time, maybe stick? Or would that just fail and not ever fix itself after?

Anyone with similar experience and possibly some fixes? Thanks

Matt

SunnyRayToronto

Yes,.... month and year posted on top of negative battery post. 2004,... time to change car battery anyways. Car battery should be changed every 7 years, regardless.

Go into dyno-mode,... SEARCH! Check voltage at start, idle & 2000rpm.

Change car battery first,... if that doesn't solve issue,... then look at starter.

LILBENZ230

I disagree. This does not sound like a battery to me. And it does appear that he did use the search function since he knows about the fuse.

Search for dyno mode and check the voltage before you start the car. This sounds more like a starter misbehaving than a battery issue since it will start after you wait a few minutes.

How many miles has the car done?

mhumphri3

Car has done right around 127,000 miles. And yes, lots of searching and research has been done, but it's hard to find someone with A) the same issues, and B) a posted solution

I will check the voltage with dyno mode this morning.

tommy

I agree that it doesn't sound like EIS is the problem at all. I'd say that you're doing things right by checking the voltage first; post your readings at start, idle, and while in motion, and that will help with your diagnosis.

mhumphri3

Okay dyno mode results are as follows.

Voltage off: 12.1-12.2 V
Voltage Idle: 14.2V
Voltage 2000 rpm: 14.1-14.2 V

Ill check it in motion when we leave in a few minutes.

Glyn M Ruck

Get a battery shop to load test the battery. If fuse 52 is 20A & not corroded it could be the starter relay playing up, the starter motor itself or the EIS not reliably enabling start. See thread or Wiki on start enable.

It can also be the temp sensor or CPS. The start enable process interrogates both before enabling start.

Good luck!

Glyn M Ruck

Here:

https://mbworld.org/forums/c-class-w...t-process.html

EDIT: Is the car storing any codes.

SunnyRayToronto

Arghhhh,... always spinning,...

The stamp shows the car battery is 8 years old,.... car battery should be changed at 7 years as routine maintenance,.... its time to change car battery anyways.

I told OP to "Go into dyno-mode,... SEARCH! Check voltage at start, idle & 2000rpm." Clearly that means SEARCH for how to get into dyno-mode,.... I don't want to post all the steps everytime,.... nor do you.

BTW, just rev in neutral to 2000rpm instead of going "in motion",.... safer.

Voltage idle (about 700rpm) should be around 13.6V,... so 14.2V is a bit high,...
Voltage off is a bit low,.... probably battery showing its age

mhumphri3

I appreciate all of the info and advice guys. I have a few things to read over and test now. Much appreciated

edgarinho10

It could also be a shifter issue. I ran into one yesterday but gladly managed to fix it

It doesn't sound like the battery either

Glyn M Ruck

That is a very good point. Next time it does this put your foot on the brake & move the shifter around briskly. Will only start in N or P

edgarinho10

Where exactly are you located? Depending on your location it could just be the starter itself being stuck or a solenoid problem.

Do you attempt it repeatedly and then it starts or just give it some time and then try again to the point where it randomly starts?

LILBENZ230

I agree with your advice, at least the part about checking dyno mode voltages. I disagree that he should immediately replace the battery. It's nice to do for preventative maintenance but until it causes a problem it's not an absolute must. Anyway, it was mostly the tone that ALL CAPS typing assigns you that I disagreed with.

CPS is a good call I didn't think about. Does the car ever stall out or anything once it is running? Sometimes the CPS will act up when the car is warm and be fine when it is cool.

mhumphri3

Car has never stalled while running, which is why I had kinda ruled out the CPS being the issue. I don't repeatedly try to crank it when the issue pops up, just wait a few minutes and it tends to start up after that. I think the longest it hasn't started is about 5-10 mins wait. Ive thought maybe a neutral safety switch, but haven't tried moving the shifter when it happens. Next time it pops up I'll try to move the shifter to neutral and see if that fixes it.

Also, I double checked the voltage again, still 14.2 for idle and startup voltage. 2000 rpm test shows the same as well.

edgarinho10

Have you tampered with anything lately? Maybe check for stored codes or take it to a local Indy shop that carries SDS.

LILBENZ230

Your alternator is fine. 14.2 is the correct voltage.

Glyn M Ruck

+1^

SunnyRayToronto

Idle should be closer to about 13.8-ish,.... I've never heard of idle voltage being same as voltage at 2000rpm. SeARCH,.... hey, it's not ALL CAP this time,.... thus, I must be improving,... well, at least according to somebody,....

LILBENZ230

When my car had a 7 year old weakened battery with a 12.2 voltage before start, it would immediately charge at 14.2 even at idle. Now that I have a new battery that is 12.7 before starting the alternator charges at 13.5 or so at idle. Sometimes as low as 13.1, but it has 143000 miles on it and isn't in top shape anymore.

The point is that as long as the voltage doesn't exceed 14.2 - the correct voltage - he is fine. If it were spiking to 16 as we have seen them do with failed regulators he'd have a host of strange electrical things happen in all likelihood. And he would be getting the alternator/battery warning.

Whatever is wrong here is not charging system related. Given all the information I have to say it sounds like a starter acting up.

Glyn M Ruck

And that is exactly what it should do. 14.2 volts is the regulator cut out point.

mhumphri3

Had another no start today, 10 minutes later it started right up. I'm really starting to lean towards the starter being the issue. Pain considering I'll have to drop the exhaust to get at it, but it is what it is I suppose.

Also, I tried starting it in neutral when it didn't start last and it still didn't start. Wife came out to try and start it while I listened to the relays and it started up again. It's a moody beast, this one...

Does anyone know which relay is the starter? I found one picture online but the fuse diagram in the front fuse box doesn't specify which relay does what.

Glyn M Ruck

https://mbworld.org/forums/c-class-w...-d2b-most.html

mhumphri3

Much appreciated.

niceguyftx

Could be a long shot for you, but it worked for me and have had no problems since! Of course this fix is for manual transmission

https://mbworld.org/forums/c-class-w...1-new-fix.html