540i no electricity!

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Adam230K

MB Enthusiast
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May 1, 2007
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German oil burner
I knoowwww this is a Mercedes forum but i have a problem which may sound relatively simple to car mechs, and i feel a bit stranded on the bmw forum so i'll give it a go here. If i'm breaking any rules just delete the thread.

The car hasn't given me a single issue to date, but it has now broken that record. Yesterday I tried to start the car it just went 'CLICK' and all power is now cut from the car, its like it has no battery! When i try to give it power from a charger, its like the car is forcefully trying to resist the charger while lights flicker, the power in the battery is fine aswell.

I've been told this could be a bad earth on the engine, because all power is cut as soon as i try to start the engine, if i do anything else the power will stay on.

Where do i start? :confused::doh:
 
Is your battery the kind where you can check/refill each cell? Worth a check as it costs nothing.

Sorry I can't be of more help, good luck.
 
there should be an earth strap somewhere, might be loose.
does sound like an earthing fault.
you could try (at your own risk) as a temporary measure using a good thick jump lead from the earth terminal onto the engine (lifting point or whatever). Might be a good idea to disconnect positiove while you arrange it first.
Also check the condition of the earth terminal to body connection (usually near the battery)
 
Try connect jump leads. negative straight onto the engine someplace and positive to the battery. Might be a stretch if your batteries in the back though.
 
If the battery has good voltage and the car only clicks I would check the starter motor next. You could measure the battery voltage as you turn the key to the crank position. If the voltage drops below 10.5v while doing this I would say poor battery, if this is the case its possible to maybe possible to view the battery fluid under the screw caps. you will see one bank of cells fizzing (bubbling water) if a cell has gone down just to confirm a dead battery, if it has then its a new one.

If the battery appears ok, Then my money would be on a sticking or faulty starter. A decent sent of jump leads from a running car will start it if the battery is dead. but not if its a stuck starter. You can try tapping the starter with a hammer for starters, If the starter is stuck it will quite often cause a clicking noise of the relays or sometime the impression the power has been lost until you turn the key off and on again.

Give this a try as it wont cost anything, Maybe half an hour stood out in the cold!

let me know what you find!
 
Put a test light across the battery
Does it come on?
Does it stay on whan you turn to start?
If no to either of these, your battery is either VERY flat or shot.
 
Hi,
If the battery is good like you say, i,m almost certain it will be the starter motor, you could try tapping the starter with a hammer or the like and try it again, had this on one of my old M5's went on for a few weeks i gradually had to hit it harder and harder to get it to operate, eventually having to replace it.
 
New development:

I seem to have got the car started by giving it a jump lead power source from another battery, but whats weird is as soon as i touched it to the terminal there was a very bright spark and the whole car came on like normal and it didnt require the jump lead to stay connected to start the engine. It started regardless. So strange...
 
Possibly a loose or bad connection at the battery post or earth strap in the boot?
 
I do need to find the earth strap, i'm not sure if its on the engine or in the boot on this model. I'll have to find that out, but thanks to all who attempted to help me in this thread!
 
I'm pretty sure its on the engine and I also think there are some issues with the earthing strap and there is a mod you can buy to rectify this. I'll ask my nephew he's the BMW guru of our group running 2 himself.
 
There will be an earth strap from the battery to the body and from the engine to the body.
 
New development:

I seem to have got the car started by giving it a jump lead power source from another battery, but whats weird is as soon as i touched it to the terminal there was a very bright spark and the whole car came on like normal and it didnt require the jump lead to stay connected to start the engine. It started regardless. So strange...

By all means check earth straps, but if you were putting the jump leads straight to the battery, I would suggest there is a problem with the connection between the battery terminal and the main cable OR still possible, a dodgy internal connection in the battery.

Remove both battery leads (make sure you have all radio codes etc). Use hot water to remove any verdegris, clean posts/connections with a wire brush, and smear vaseline on the terminals.
 
I do need to find the earth strap, i'm not sure if its on the engine or in the boot on this model. I'll have to find that out, but thanks to all who attempted to help me in this thread!

There are usually several earth straps on modern cars.
 
Are we seriously to believe that a BMW forum could offer no help to this poor man ??:dk:
 

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