[infraboy]

Strange problem with my 335i. Car suddenly wouldn't start, lights/dash would turn on but wouldn't fire up. I checked the battery compartment and it was partially flooded with water

I pulled the battery out and cleaned out all the water and reconnected everything, put the battery on a charge just in case. Tried starting the car a again and still wouldn't crank.

Final solution was to hook up a battery booster with the leads under the car and the car cranked and started

Figured it was the battery was toast, so I replaced it with a new one. But same problem persists, car will start if I boost/jump it but not on its own.... am I missing something? Doesn't appear to be any of the fuses or anything...

[Mastermixlee]

Hmm if it's starting with the battery booster but not with a brand new fully charged battery I suspect it would be a connection or a fuse. The red cover above the battery actually has blades that although don't look like fuses act as them. So it could be under there. I don't have a picture to hand but if you clip off the top red battery cover from the black retainer you should see where wires connect up for the distribution rail/fuse blades. If ones of those has gone or broken connection that could be the cause. Seems odd that it would start with battery booster otherwise.

[david in germany]

Bad ibs?

[335dlci]

If your battery is in a pool of wster. The connection st the red cables that go through the body are probably rusty. I have seen it before. Because it started with a jumper gives the starter direct power in a cable 5 ft long. You may be replacing your whole positive cable from trunk to fire wall jump service port along with the valvetronic motor supply cable also.

[Bimmer Pleaser]

How did you get a pool of water in your battery compartment 😲???

Probably messed up the conductors, distribution/overcutrent protection components. Maybe blown fuse. Check positive connection from trunk to the front, and measure positive to ground resistance.

[smallseafishie]

Where are you putting the boost pack? Under the hood or at the battery in the trunk? If under the hood, try at the battery and report. The little thing that sits on top of the battery that connects to the positive terminal is a fuse block. There is a fused circuit that sits between the battery itself and the underhood jumper terminal / alternator / starter.

[335dlci]

Originally Posted by smallseafishie

There is a fused circuit that sits between the battery itself and the underhood jumper terminal / alternator / starter.

According the diagram there isn't one... juat a direct connection to the jump starting port.

[vilord]

another possibility is the ground strap from the engine to the body... where are you connecting the booster pack?

[infraboy]

Connecting the booster from the connections under the hood is what I did.

[vilord]

where'd you connect the black cable though? under the hood on mine there is a red connector for the +, but there is no black for -

[Emilime75]

Originally Posted by vilord

where'd you connect the black cable though? under the hood on mine there is a red connector for the +, but there is no black for -

Dude, BMW screwed you with the old "Let's not put a ground anywhere in engine compartment" trick...like, maybe an engine block, or a metal component bolted to said block, or...

[vilord]

I know I can get ground anywhere. If I put the ground cable to the body (extra long nut near coolant tank, or the suspension crossbeam bolt for example) then the ground to the starter has to feed through that crappy ground strap that corrodes through. If I connect it to the engine, it doesn't go through that strap.
Knowing where the OP connected his jump box will help with diagnosis.

[david in germany]

Originally Posted by Emilime75

Dude, BMW screwed you with the old "Let's not put a ground anywhere in engine compartment" trick...like, maybe an engine block, or a metal component bolted to said block, or...

What the heck are you talking about?? there is a ground point under the hood right next to the coolant expansion tank. It looks like an extra long nut with no paint on it (to be conductive).
You can see it in the left of this picture and almost every modern bmw has it in a similar location.

[vilord]

Not everyone reads all 300 pages of that damn manual...

[david in germany]

Originally Posted by vilord

Not everyone reads all 300 pages of that damn manual...

I have just wanted to use that smiley. It was the perfect opportunity. But joking aside, BMW always has the best grounding point available for you already established to use under the hood.

[vilord]

I pulled out my manual, and sure enough, there it is. Now to find some touch-up paint to fix where I scratched the strut tower from the last 5 years of jump-starting other people's cars.

[Emilime75]

Originally Posted by david in germany

What the heck are you talking about?? there is a ground point under the hood right next to the coolant expansion tank. It looks like an extra long nut with no paint on it (to be conductive).
You can see it in the left of this picture and almost every modern bmw has it in a similar location.

You're missing the point, sir. Plus, I don't need to RTFM to find a grounding point in an engine bay, but thanks.

[david in germany]

Originally Posted by Emilime75

You're missing the point, sir. Plus, I don't need to RTFM to find a grounding point in an engine bay, but thanks.

You are missing the point. You can see my post was made in good fun. but if you think BMW didn't put a grounding point under the hood as you stated in your post, you are dead wrong. with the way BMWs are built and wired (using IBS) BMW only recommends you use that grounding point under the hood for jumping or damage could occur to the electrical system of the car. If you think otherwise, maybe you SHOULD read the manual.

The real point of this thread is the issue with infraboy having problems with starting.

infraboy, have you checked the IBS on the battery?

[Socket]

Originally Posted by Bimmer Pleaser

How did you get a pool of water in your battery compartment 😲???

Probably messed up the conductors, distribution/overcutrent protection components. Maybe blown fuse. Check positive connection from trunk to the front, and measure positive to ground resistance.

Water in the battery compartment is typically from water leaking in from a poor seal around the tail light.. Is common where people have fitted aftermarket tail lights or if the stock tail light has become loose

[Cruiser124]

Originally Posted by Socket

Water in the battery compartment is typically from water leaking in from a poor seal around the tail light.. Is common where people have fitted aftermarket tail lights or if the stock tail light has become loose

That's what happened with a 335 I picked up except it was on the other side and fried the amplifier. Tightened the mounting nuts and no more leak.

[Emilime75]

Originally Posted by david in germany

You are missing the point. You can see my post was made in good fun. but if you think BMW didn't put a grounding point under the hood as you stated in your post, you are dead wrong. with the way BMWs are built and wired (using IBS) BMW only recommends you use that grounding point under the hood for jumping or damage could occur to the electrical system of the car. If you think otherwise, maybe you SHOULD read the manual.

Apparently, you've never heard of sarcasm and proceeded to get your panties wadded up.

[david in germany]

Originally Posted by Emilime75

Apparently, you've never heard of sarcasm and proceeded to get your panties wadded up.

I type with a smile 80% of the time. Ever heard of going "ranger"?