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How dead does a battery have to be?

1048 Views 42 Replies 10 Participants Last post by  Slk-razy
Hi,
The last three times when I tried to start the car, it took like five or six tries to get it to start. When I move the key to the engine crank position all the idiot lights on the gauge cluster are lit, and the radio and HVAC fan start and the bottom display adds P for Park and S for Sport, but the engine does not turn over.

I took out the key and tried multiple times and then suddenly after about five tries the car starts.

I had problem today at 3:00 PM when I went to pick up my son, and again when we stopped at the store on the way home. It's 4:15 and I just went out and tried it again and of course now it starts repeatedly. I displayed the voltage level by moving the key one notch clockwise and hitting the reset button three times and the display says 11.9 V prior to starting. With the engine running it says 14.1 V.

I don't remember what the voltage was at 3:00 PM when I had the problem, but my question is: Would voltage down around 10 V make the car not start? I guess I should just replace the battery and see if that fixes the issue, I did have to jump the car one time when I was working on it and raises and lowered the top a few times without the engine running.

The only other thing that I can think of that is causing the problem is the key: I only have one and maybe something there is the issue.
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No need to register. What he probably means that if your car has BCM (Battery Control Module) you need to tell that module that a new battery has been installed. Basically reset the module.
But our cars don't have a BCM,so no need.
As to AGM,I replaced my ordinary OEM battery by a Varta AGM 6 years ago. Still going strong. So draw your own conclusions. ;)
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I’m certainly no expert on this, but when I had a similar problem, it turned out to be the K40 relay. It cost me about $200 and took about 15 minutes to change. My car has started every time I turned the key since.
I’m certainly no expert on this, but when I had a similar problem, it turned out to be the K40 relay. It cost me about $200 and took about 15 minutes to change. My car has started every time I turned the key since.
fyi... member has a r171... you have a r170 :D and so he does not have a K40 :D
Also as discussed before, some of us get all the lights on the dash and give the car 5 elephants before cranking. Just give it chance to decide if it wants to play.
@Berapotter
Thanks for that tip!
When the car won't start I now use the above suggestion of waiting five seconds and that has been working, so that means it's not the battery, but I don't know what failing part that waiting five seconds is helping.
EIS

Mercedes Benz Electronic Ignition System (EIS) Diagnosis

Wow something I suggested works!.......I'm off for a lie down :eek: o_O
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@Berapotter
I just used your suggestion again today and it worked! Thanks so much otherwise I might have been stuck! You deserve more than a lie down!

(Also, I think this confirms it is not the battery since waiting 5 seconds couldn't "fix" a dead battery).
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Yea, well, you still better get it diagnosed cuz next time, 5 elephants ...or 50 may not get you going again (y)
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I've had the same problem ever since I got it over two years ago..

It's not 5 elephants for me, just wait until the fuel gauge starts moving, and it's all ok. BUT only needed when the car is cold..

I've changed the most likely culprits, the CAM and CRANK shaft senors, but same problem. I've given up finding the problem, it's not that big of a deal for me..
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So if it happens on the V6 and V8 it isn't an engine issue per se.
Might be a little capacitor taking a tad too long or the SAP not running up quick enough or even the fuel guage or sender. The amount of computing power 15 years ago has now taken a fair bit of wear and tear.
And of course for some of us the cars are getting a little bit older and like me not as quick from a cold start😇
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Yeah, that's what I'm thinking as well..

It's like it take "a few" seconds for the car to "boot up". The display is dead for "a few" seconds, then everything "turns on" at the same time. I just look at the fuel gauge, because it's easiest on the eye.. AND I get a feel for how far I can go this time :D :D.


What's "The SAP"?
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Ah, the good old days. I had a 1965 Daimler V8 which was reluctant to start. But not computers...no, no. You used to turn the key and you would hear a ticking, which got slower and then stop. Only then would the mighty V8 fire. The ticking was the fuel pump and it would slow as the floats in the reserve chamber slowly cut of fuel when they were filled!

At least I knew what it was. You could also tell the state of the battery, depending on the "rate of ticking!" :LOL:
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SAP Secondary Air Pump.
The air pump that send cold air to the exhaust on start-up. Runs around 30 seconds on cold starts. Part of the emissions "thing"🥴
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Oh, I see..

Interesting.. I have seen a few threads on here where that's gone completely dead, but nothing about what happened BEFORE.. Need to check how much one of those are brand new and if it's not to bad, change it just because..
I'm only offering a few suggestions. Don't spend money based on the musings of an idiot,🤡😱
I liked the fuel pump comment by Rik_In_Taz👍
SAP Secondary Air Pump.
The air pump that send cold air to the exhaust on start-up. Runs around 30 seconds on cold starts. Part of the emissions "thing"🥴
Secondary air pump was 1 of the last defered maintaintence items i replaced within months of purchasing, still makes a high frequency fan noise few minutes when starting not jet engine loud though! Bosch no star emblem $275. USD
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SAP Secondary Air Pump.
The air pump that send cold air to the exhaust on start-up. Runs around 30 seconds on cold starts. Part of the emissions "thing"🥴
Sorry! My parrot was driving crazy!
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How old is the battery? no idea? Time for a new battery
charging and recharging a dead or dying battery cel/s will not fix the problem

someone has a bad heart, you get a new heart, not a new pacemaker

and you should never run the roof without the car being on.
once in a while, sure, to show off but not make it a habit
LMAO Jeff. What a great analogy!
When in doubt get that battery out!
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That is Walmart's brand :D
Yes and could be made by East Penn in PA or Exide in India. Interesting my Canadian Tire AGM Battery which is East Penn, perhaps out of their Canadian operation ( they are a family business) has a 5 yr replacement warranty I believe (papers are down in the car) and it is solid so far which makes me think it’s perhaps the charging system. When the car is running what is the voltage shown in the display?
I have had 13 Benz cars in the last 35 yr. and had to buy maybe 3 or 4 batteries in that time including the SLK320 ex Japan car before the one. I have bought conventional and the last two AGM and they have had one thing in common. All were the correct group and size for the car in question per MB.
Ignorance is bliss I guess because I never in all my life with my cars going back now 63 yr from the time I got my first car (VW Beetle) have I ever heard of registering a battery. Then again I have read on this sight opinions about AGM batteries not being suitable for these cars but who knew? My experience says “ says who?”
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