X250 engine earth strap and failed hot start.

[Techno]

I've found several threads across the web detailing the same symptom of failure to re start a hot engine.
Normal starting from cold is fine but after a journey the first attempt at restart often fails.
The popular answer is to replace the engine earth strap.

This picture borrowed from O&AL
Broken Link Removed
I've not had chance to prove it yet but I did 10 consecutive cold starts and all fired as fast as you can say 1 2 3 with no hesitation. I've replaced with a shag of 70mm welding cable.

 

[Techno]

Some may ask why would being hot change things?
I believe it is to do with increased cylinder pressure and thus higher cranking load.

 

[TheBig1]

as you know, but others may not, the easy, belt and braces way to check if its the earth strap is to connect a good jump lead from the battery negative to the engine block. if the problem goes away with the jump lead connected, then its fair to assume the earth strap has rotted. a pretty common fault on many different vehicles, not just Fiat ducatos

 

[Jon and Shell]

It could be another reason Andy.

The resistance in the earth strap could cause all sorts of problems with the analogue inputs to the ECU and this could screw things up.

 

[Ed Excel]

Set your Multimeter to the lowest resistance setting and start the engine. Touch a probe on the negative battery pole and the other to a bolt on the chassis. You should get at least 0.3 Ohms. If the readout stays at zero, the earth cable or chassis bolt is either loose or corroded. Do similar between an engine bolt and a chassis bolt. If the instrument doesn't register you've a problem with the engine strap.

 

[Techno]

My earth strap doesn't look rotted but it doesn't look especially healthy. Why use bare copper at all?

 

[vin0114]

Thanks Ed, very good tip.

 

[Ed Excel]

It's not a great environment they're in and PVC's only happy up to 70C. I imagine these straps can get hotter than that.

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[Techno]

It could be another reason Andy.

The resistance in the earth strap could cause all sorts of problems with the analogue inputs to the ECU and this could screw things up.

Would this not be the same engine hot or cold? remember it is ONLY a hot engine fault.

 

[Ed Excel]

If you're starting off with a high resistance connection then any temperature rise will exacerbate the problem.

 

[pappajohn]

Easiest way to test a copper earth wire is to grasp it firmly then pull and push as hard as possible.
i've seen a few which looked good but soon broke when sujected to the above.

If it doesnt break its good.

Doesnt mean the connection between cable and battery/engine/body is good though.

 

[Techno]

I have good connection now John so we'll see next time I restart it hot

 

[Techno]

I've had many a car over 16 yrs old (one over 20) and never had an earth strap problem. The reason I started this topic is because it seems to be particularily common to X250's

 

[Ed Excel]

Did your cars have an engine compartment floor pan? Has the x2/50? My car has. It gets mentioned in every MOT as an excuse for not checking anything behind it.

 

[Techno]

no and yes

 

[Badknee]

I've had many a car over 16 yrs old (one over 20) and never had an earth strap problem. The reason I started this topic is because it seems to be particularily common to X250's

I've been driving for about six months now and I've never had a problem

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[Jon and Shell]

Would this not be the same engine hot or cold? remember it is ONLY a hot engine fault.

The strap could warm up with the continuous load of charging your battery bank. It provides the negative for your alternator remember!

Don't get these problems with Transits........

 

[Techno]

Don't get these problems with Transits........

Exactly

 

[Techno]

Perhaps more interestingly.
As I said the commonly reported fault is a failure to restart when hot BUT that is only on the first attempt, they start on the second go.

 

[Ed Excel]

That's Fiat design for you. Looks good!!

 

[Techno]

Fiat have a growing portfolio of problems that they try to dismiss. Recent example being the new 500 that they have conceded after much pressure from watchdog etal. Ducato scuttles still leak etc

 

[Ed Excel]

Stiction. The excuse our engineering tutor gave for something reluctant to move at first attempt.

 

[Moodybrook]

Excuse my ignorance but are you discussing a failure to turn over or a failure to fire up ?
If a failure to fire surely it is a fuel supply problem, in a diesel.
I've come across corroded connections never seen a mid cable failure. ? Must be a pretty historic van ?

 

[tonyidle]

Set your Multimeter to the lowest resistance setting and start the engine. Touch a probe on the negative battery pole and the other to a bolt on the chassis. You should get at least 0.3 Ohms. If the readout stays at zero, the earth cable or chassis bolt is either loose or corroded. Do similar between an engine bolt and a chassis bolt. If the instrument doesn't register you've a problem with the engine strap.

Er ............... you should get AT THE MOST 0.3 Ohms

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[ukbill]

although this maybe different i have had a light problem 3 times now on my van and all has been with the earth i believe overall the wiring on the fiat is sub standard

 

[gloworm]

I read about this earth strap problem a few years back. Changed ours then for an insulated one, and its been fine.

Eric

 

[Techno]

Er ............... you should get AT THE MOST 0.3 Ohms

and if the reading stays at infinity not zero
Zero is good! it means the resistance is lower than a cheap test meter can register.

 

[WAG2CRU]

Our X250 base had intermittent problems with the windscreen wipers and cruise control, a second earth strap was the cure.
Earth problems are not confined to Fiat though, the early Freelander 2 often benefits from a second earth strap which solves all sorts of random electrical faults and improves gear changes on the auto box..

 

[jockaneezer]

Fix It Again Toni
Having said that, I had an immobiliser fault on an old V40, wouldn't crank, all sorts of lights illuminated on the dash. Removed the earth strap from the gearbox and found the junction was covered in that white corrosion powder that forms on aluminium. A wire brush and smear of copper slip sorted it out.

 

[Techno]

I'm sat here now with a hot engine and I am unable to recreate the fault so it seems to me that the reports are correct. My fault has existed since acquiring it over two years ago but because it always started second try I ignored it.