Technical Earthing issues

[Chundle]

Hi all,

Having the dreaded earthing issues, I've changed the strap underneath the battery tray and still not having much luck.

I can start the car by negative battery terminal to heat shield via a jump lead so I'm still assuming it's the earth.

Any ideas please

(Posted here because it's a bit more active than the Abarth forum)

 

[GettinBetter]

Everything else working fine?
Was the old bottom earth strap badly corroded and in need of a change?
Did you meticulously clean the terminals/bolts of both ends on the new strap?

Is the top cable in good condition, and in particular the bottom ferrule connection with the bolt hole. The copper inside the ferrule can oxidise and create an insulation barrier to high currents, which is difficult to measure with a standard multimeter. As the current used to calculate the resistance is so small it isn't inhibited by the oxide.

Just a few things to ponder.
GB

 

[The Panda Nut]

What are any other symptoms, are other electrical systems affected eg lights, and steering. If its just a starter maybe wiring at the starter is an issue. So check and clean the main cables on the starter and the battery live.
The earth needs the right sized hole at the end, if eyelet is too big it could affect contact and may need sandwiching with some copper washers. If needs be add another earth. Chase the earth back from the battery too to therear or the engine compartment. This is relatively low and is just as important as the engine / gearbox to the front chassis leg.

 

[Chundle]

Everything else working fine?
Was the old bottom earth strap badly corroded and in need of a change?
Did you meticulously clean the terminals/bolts of both ends on the new strap?

Is the top cable in good condition, and in particular the bottom ferrule connection with the bolt hole. The copper inside the ferrule can oxidise and create an insulation barrier to high currents, which is difficult to measure with a standard multimeter. As the current used to calculate the resistance is so small it isn't inhibited by the oxide.

Just a few things to ponder.
GB

Everything else fine, radio, lights etc working with no issues. I've had the yellow triangle with the ! inside on the dash for a little while before this however.

See attached old strap and new one is

110 AMP RATED 16MM² BLACK BATTERY CABLE 300MM

Battery is back in at the mo but can take out to investigate, can't say I cleaned the ends of the new strap - should I have roughed it up a little?

 

[Chundle]

What are any other symptoms, are other electrical systems affected eg lights, and steering. If its just a starter maybe wiring at the starter is an issue. So check and clean the main cables on the starter and the battery live.
The earth needs the right sized hole at the end, if eyelet is too big it could affect contact and may need sandwiching with some copper washers. If needs be add another earth. Chase the earth back from the battery too to therear or the engine compartment. This is relatively low and is just as important as the engine / gearbox to the front chassis leg.

Bar the warning light, no. Haven't checked the wiring at the starter yet and I think the earth was the right sized holes. Could I just earth the battery to another location in the engine bay?

 

[irc]

300mm cable is only CHASSIS to GEARBOX, isn't it?
Or did you change the other one too?
If the problem is the BATTERY to CHASSIS cable giving up under load then that would cause this problem.

 

[Chundle]

300mm cable is only CHASSIS to GEARBOX, isn't it?
Or did you change the other one too?
If the problem is the BATTERY to CHASSIS cable giving up under load then that would cause this problem.

300mm is from chassis leg to gearbox yep, that's the one I replaced yesterday.

Battery to Chassis is the one in the middle right? Apart from that fraying at the top of the cable on the negative terminal, it looks ok - wouldn't be expensive to replace it though if needs be

 

[The Panda Nut]

Bar the warning light, no. Haven't checked the wiring at the starter yet and I think the earth was the right sized holes. Could I just earth the battery to another location in the engine bay?

If you have the triangle light, press the menu button on your dash and see if it tells you why, sometimes it does.
The short answer is yes you could do this, but beware if you have resistance from bad connections you do have an increased fire risk. Check the battery terminals and connections are nice and clean and look at the back of the engine left side as you drive for the other earth point. Has the battery been replaced. I wonder iof the battery poles are smaller than standard and the poor connection is at the battery. The clamp tight but actually loose?

 

[The Panda Nut]

300mm is from chassis leg to gearbox yep, that's the one I replaced yesterday.

Battery to Chassis is the one in the middle right? Apart from that fraying at the top of the cable on the negative terminal, it looks ok - wouldn't be expensive to replace it though if needs be

300mm is from chassis leg to gearbox yep, that's the one I replaced yesterday.

Battery to Chassis is the one in the middle right? Apart from that fraying at the top of the cable on the negative terminal, it looks ok - wouldn't be expensive to replace it though if needs be

No I think not the battery is earthed at the back of the engine the engine / gearbox earth is secondary earth to aid continuity. If you have access to another battery try swapping as battery wekness is a known regualr with these cars. DOnt necessarily trust a new battery to be a good battery either.

 

[The Panda Nut]

300mm is from chassis leg to gearbox yep, that's the one I replaced yesterday.

Battery to Chassis is the one in the middle right? Apart from that fraying at the top of the cable on the negative terminal, it looks ok - wouldn't be expensive to replace it though if needs be

There are various earthing points that may impact on anything in the system. One under the heather box, one in the boot behind the boot sill trim and one on the bulkhead as well as the lighting ones. Most are internal or in dry areas so should be OK.

 

[irc]

300mm is from chassis leg to gearbox yep, that's the one I replaced yesterday.

Battery to Chassis is the one in the middle right? Apart from that fraying at the top of the cable on the negative terminal, it looks ok - wouldn't be expensive to replace it though if needs be

Not terribly expensive, think it's either 600mm or 800mm, but can't remember which at the moment (someone on here will know). The starter uses this earth path (and any others electricity can find) for a really big pull of power when engaging and starting to turn the engine. Bad lead = no or slow cranking. Don't fail as often as the lower lead, but do still fail sometimes.
Because you can crank with a jump lead from battery to engine block, it's a definite possibility.

EDIT Just measured on a 595 and it appears to be about 580mm (but its a bit crowded in the engine bay, so can't guarantee accuracy)

 

[John202020]

Clean the contact area not the lead at each end especially where it meets the car chassis.
There's no harm using another cable at the other end any suitable bolt will do to the body

 

[Chundle]

I'm going to go ahead and check the other earthing points too, I was driving around in it and it only failed to start once I was at my last destination. The roads are crap in the UK and I assume I've gone over a pothole at some point and it's loosened something or snapped something off. The battery itself is fine, I had it tested when I broke down.

 

[John202020]

If a jump cable from the battery to the block fixes it, it's a simple earthing issue or it's installation?

 

[Chundle]

If a jump cable from the battery to the block fixes it, it's a simple earthing issue or it's installation?

Exactly this, but the earth from the battery looks ok hence why I'm going to look at the earthing points. You can go from the negative termal to the heat shield and the engine is turning over, obviously won't start but it's trying lol

 

[John202020]

It obviously won't start but it's trying lol

No it should start no problem if it cranks over without issue

 

[Chundle]

No it should start no problem if it cranks over without issue

It starts yeah

 

[Chundle]

To report back, I FIXED IT!

Went back on myself and cleaned every connection, every nut and every bolt on the way down from the battery. There was a fair amount of rust on the end of the battery negative cable so got that down to the original metal, found a fair amount of rust around the earth strap to gearbox bolt that it was sitting on too.

Some of the nuts were also very loose, maybe because I rushed putting it back together yesterday but I tightened them so much I thought I was going to snap a couple at one point lol!

And as a bonus the warning light has seemed to clear itself, obviously was an electrical fault.

Touch wood all good, thanks everyone for the ideas and hopefully be the last time I have to do that for a while, my hands are cut to f*ck

 

[Chundle]

To report back, I FIXED IT!

Went back on myself and cleaned every connection, every nut and every bolt on the way down from the battery. There was a fair amount of rust on the end of the battery negative cable so got that down to the original metal, found a fair amount of rust around the earth strap to gearbox bolt that it was sitting on too.

Some of the nuts were also very loose, maybe because I rushed putting it back together yesterday but I tightened them so much I thought I was going to snap a couple at one point lol!

And as a bonus the warning light has seemed to clear itself, obviously was an electrical fault.

Touch wood all good, thanks everyone for the ideas and hopefully be the last time I have to do that for a while, my hands are cut to f*ck

 

[GettinBetter]

Went back on myself and cleaned every connection, every nut and every bolt on the way down from the battery. There was a fair amount of rust on the end of the battery negative cable so got that down to the original metal, found a fair amount of rust around the earth strap to gearbox bolt that it was sitting on too.

That's the only way to do it, and thanks for updating on your progress/solution.