Where should my batterys earth be connected to?

Hi,

I have a 90 with a v8efi in it. I've had a few starting problems with it. Battery seems fine, alternator seems fine.

I've been reading some other threads. I think my next move is to check everything is earthed correctly.

Currently i have the earth of the battery connected directly to the chassis through a short thick black cable.

Is this enough, or should i have another to the engine bay, or starter etc.

Anyone with a standard 90, how many earth cables are taken off your battery?

Thanks in advance.

Is there a good earth to the engine casing?

Also, any more detail about the starting problems?

Just the one earth lead directly off the battery to the chasis.

Worth gradually undoing all the chasis earths, cleaning with wire brush/emery paper, protecting with WD40/silicon spray/copper grease and redoing up tight

mundungus said:

Is there a good earth to the engine casing?

Also, any more detail about the starting problems?

Click to expand...

A typical day, i can get in, start it fine, drive for 30 mins on the motorway fine, arrive get out for 5 minutes, get back in and try to start. It turns over very slow and doesnt fire up like the battery hasnt charged. I've put a volt meter accross the battery, it reads fine. Watched it as i turn it over, it doesnt drop below 12v - fine. I can get it started easily with a jumper pack for some reason. But halfords say the battery is fine and oversized if anything, and i've done the alternator tests and it seems fine.

Very confused!!

There's no earth to the engine, just one to the chassis.

Station House said:

Just the one earth lead directly off the battery to the chasis.

Worth gradually undoing all the chasis earths, cleaning with wire brush/emery paper, protecting with WD40/silicon spray/copper grease and redoing up tight

Click to expand...

I'll try it, thanks.

There should be an earth strap onto the engine/gearbox. If you think about it, there are not many metal to metal connections from the engine gearbox assembly to the chassis, down the props to the axles, then the axle is sitting on lots of rubber bushes. The engine and gearbox sits on 4 big rubber mounts, see where this is going? If the engine earth is poor or non existent the favorite route for starter current is up the handbrake cable melting it to oblivion.

The factory fit on my 90 was two earth straps from the neutral terminal, one to the bulkhead outrigger support, and one to the top of the main gearbox. I then added one from the chassis to a starter motor bolt.

If you're convinced your battery and alternator are ok (but I wouldn't trust anything Halfords tell you) then its just as Discomania says.

Chances are there's an earth strap from the chassis to the engine or gearbox that has broken down. If its one of the copper braid type, these are notorious for breaking down over time causing their resistance to increase, which becomes a problem when pulling the high current necessary to turn over the engine.

Just replace it with an insulated earth lead. Either from the chassis to the engine or gearbox or starter, or as suggested from the battery to the gearbox.

You could test this theory. When you next have the problem, take a single jump lead between the engine and the battery earth terminal. See if that makes a difference.

What Disco says. I have two heavy earth cables direct from my battery. One to the chassis and one to one of the starter mounting bolts. I also have an additional cable from the chassis earth point to the underneath of the cubby box under the drivers seat which is the main ECU earth in a TD5.

I seem to remember reading some where that the earths all meets under the bonnet against the bulkhead next to the servo?

I'm sure u guys have got it right. Makes sence to me. And the jumper pack starts it because I connect the earth of that directly to the engine. I'll try and add the extra earth direct to the engine or starter motor, check the existing earths the take it from there. I'm not certain about the alternator, but they tested the battery with a bosch tester and the printout said good, surely even they can't get that wrong! Lol

Just done the jumper cable check. I ran a jump lead from the bat -ve to the engine block. IT STARTS LIKE A NEW CAR . so the problem is definately the single earth to the chassie with a poor connections. It even affects the charge rate. Time to buy some large cable!!

Good result in tracking it down - and even better not too many pennies to sort

Halfords sell battery cables made up for about 4 or 5 quid, depending on length. I recently put two on my daily driver after the original broke and everything died just as I pulled out on to a busy roundabout. Proper brown trouser moment.

Cheers, i've just seen them on the website. That'll save waiting for delivery. I just need to find somewhere to bolt it to my engine block now.... I have and idea though. I'll have a look in the morning. These 30mph winds aint sounding too appleling lol

Anywhere directly on the block will do. I used one of the starter mounting bolts. Dont bolt it to manifolds or ancilliary mounting brackets.

Remember that even if your battery is registering 12-13v and above it still may lack cranking power to turn an engine over, the only real way to test the cranking power is to crank it

Also on my 200Tdi i have the negative from the battery to the chassis and 2 straps from the neg point on the starter to the engine block and chassis.

PaulWilde said:

Remember that even if your battery is registering 12-13v and above it still may lack cranking power to turn an engine over, the only real way to test the cranking power is to crank it

Also on my 200Tdi i have the negative from the battery to the chassis and 2 straps from the neg point on the starter to the engine block and chassis.

Click to expand...

If you put a voltmeter across the battery and it drops below 10v while cranking then there's probably a problem with it. I've never heard mine turn over so fast with a proper earth connected! Sounds very healthy .

Why is it raining today!?!

Right! Finished the job today. I bought 2 black battery cables from Halfords. I connected one from the chassis to the engine block where it meets the gear box. To be honest this solved all my starter and charging problems, which suggests that the earth has trouble getting through the rubber engine mounts. I still installed the second cable anyway just for extra peace of mind. This one i put directly between the chassis and the battery -ve terminal. The origianl cable was connected to the sidestep, which seemed more likely to fail at a later date. I've also bought a earth strap to connect to the interior body. Cant hurt........

Job done. Thanks people.