Technical Starting issue - only solved with secondary earth cable

[gazflo]

I'm posting this here as a solution, but also to question why.

Our 2019 Fiat 500 recently suffered from a no-start problem - dashboard would light up but it wouldn't crank. As suggested elsewhere in the forum, the problem was diagnosed as a bad earth.

However, replacing the existing earth cable from the body to the gearbox did not solve the problem.

After much head scratching and unnecessary expense, it could only be rectified by adding a secondary earth cable from the body to the engine block (see pic).

Has anybody else experienced this issue? Why would the engine not be earthed if the gearbox is? Why would it fail now?

 

[John202020]

I would suggest, poor connection/corrosion at connection point on new cable issue

 

[GettinBetter]

I'm posting this here as a solution, but also to question why.

Our 2019 Fiat 500 recently suffered from a no-start problem - dashboard would light up but it wouldn't crank. As suggested elsewhere in the forum, the problem was diagnosed as a bad earth.

However, replacing the existing earth cable from the body to the gearbox did not solve the problem.

After much head scratching and unnecessary expense, it could only be rectified by adding a secondary earth cable from the body to the engine block (see pic).

Has anybody else experienced this issue? Why would the engine not be earthed if the gearbox is? Why would it fail now?

Not exactly, but added another earth cable from neg terminal to offside of engine, to cure a no charging problem. I too changed existing earth cables.

It's been fine ever since.

 

[gazflo]

I would suggest, poor connection/corrosion at connection point on new cable issue

Thanks @John202020 All the terminals were cleaned when the original cable was replaced. It's almost as if the gearbox wasn't earthing to the engine.

 

[gazflo]

Not exactly, but added another earth cable from neg terminal to offside of engine, to cure a no charging problem. I too changed existing earth cables.

It's been fine ever since.

Thanks @GettinBetter different problem - same solution I'm just confused how the earth from the gearbox wasn't transmitting to the engine. Strap A was checked, strap B replaced, but only when strap C was added, did it fix the issue

 

[AnthonyH]

The B wire failed at the nut. Seeing the corrosion isn't always easy, you don't have to miss much rust and the current is affected.

 

[GettinBetter]

Thanks @GettinBetter different problem - same solution I'm just confused how the earth from the gearbox wasn't transmitting to the engine. Strap A was checked, strap B replaced, but only when strap C was added, did it fix the issue

I suppose if you take into account any gaskets, sealants, threadlock, and corrosion, it is quite possible to have the earth path impeded.

 

[chris3234]

Thanks @John202020 All the terminals were cleaned when the original cable was replaced. It's almost as if the gearbox wasn't earthing to the engine.

Presumably build up or corrosion on the gearbox bots or mating surfaces
That or has been fitted with some sort of sealants between the engine and gearbox perhaps it's been removed at some point

 

[gazflo]

Presumably build up or corrosion on the gearbox bots or mating surfaces
That or has been fitted with some sort of sealants between the engine and gearbox perhaps it's been removed at some point

Thanks @chris3234 I've had a mechanic take a look and he thinks the gearbox has been removed at some point.

Thankfully the secondary earth seems to be working for now.

 

[The Panda Nut]

Thanks @chris3234 I've had a mechanic take a look and he thinks the gearbox has been removed at some point.

Thankfully the secondary earth seems to be working for now.

I bet someone put gasket cement on the mating surfaces!

 

[John202020]

I bet someone put gasket cement on the mating surfaces!

But the bolts should be a sufficient conductor?

 

[The Panda Nut]

But the bolts should be a sufficient conductor?

Well yes but I have always thought Fiats earthing odd. Other cars earthed to body and engine earthing was secondary. Its certainly odd, but seems to be a common situation.