Technical Fuel leak from rear arch, from this black box.

[BigAdam]

Afternoon.

Filled my Panda 1.1 up last week and found it leaked, not a lot, but for a long time. Today I stripped off the inner wheel arch plastic and found it was coming from the pipes on the bottom of this large black box.

My question is; What the heck is this thing for, and why is it leaking petrol?

... also does anyone have a diagram for how this plastic under the arch goes back on because I cannot figure it out.

 

[varesecrazy]

Hi

Its the fuel Evap. canister.. ( for emissions)

(In older cars it was under the bonnet )

Apparently on a 500 it can be ruined by petrol ( liquid..not vapour)

Being next to the filler neck obviously isnt ideal.. hence the warning in the 500 manual about OverFilling with unleaded

 

[bugsymike]

Hi

Its the fuel Evap. canister.. ( for emissions)

(In older cars it was under the bonnet )

Apparently on a 500 it can be ruined by petrol ( liquid..not vapour)

Being next to the filler neck obviously isnt ideal.. hence the warning in the 500 manual about OverFilling with unleaded

Only manufacturers can supply a part that is related to the fuel system but affected by fuel. A bit like fuel companies putting ethanol in fuel knowing that even 5% (E5) is not good for older vehicle fuel systems. I wonder how many people are grabbing an E10 pump nozzle without realising.
Or in my case a leaking oil cooler that when the oil gets in the cooling system it damages the coolant O rings

 

[BigAdam]

Coolio, so its the Evap. canister.

Do I just not overfill, or do I replace the little O-rings in the fittings?

I do tend to fill my car by going "full ... clunk ... little more ... clunk ... one more little bit"

 

[jrkitching]

The fuel system on the Panda/500 is designed to operate with an airspace of somewhere between 5 and 7 litres.

When refuelling, you must never add more fuel beyond the second 'click' of the dispensing pump's automatic shutoff. If you attempt to add any more fuel after this point, for example by dribbling it in, you can irreversibly damage the EVAP canister. Replacement is a dealer only part, and well north of £1000.

There is a clear and specific warning about overfilling the tank in the vehicle handbook.

 

[bugsymike]

The fuel system on the Panda/500 is designed to operate with an airspace of somewhere between 5 and 7 litres.

When refuelling, you must never add more fuel beyond the second 'click' of the dispensing pump's automatic shutoff. If you attempt to add any more fuel after this point, for example by dribbling it in, you can irreversibly damage the EVAP canister. Replacement is a dealer only part, and well north of £1000.

There is a clear and specific warning about overfilling the tank in the vehicle handbook.

I learn something new every day, I have always filled to brim, especially if doing a mileage check on a latest acquisition.
Sounds like modern cars were made for my ex wife, when the light comes on put £10 in and expect it to run all week.

 

[koalar]

I am still confused

“Filled my Panda 1.1 up last week and found it leaked, not a lot, but for a long time.”

I understand it’s the evap canister

I understand the canister can be damaged by over filling

But does overfilling cause the evap to leak?

What I don’t understand is the fill pipe and canister aren’t directly connected. The location is just handy as it above the height of the tank. Use to be under the bonnet

I doubt it’s been hot enough for the positive pressure valves to open

It’s a sealed system for gasses how can liquid be escaping and over a long time.

Leaking petrol especially near a tyre on wet roads or for following motorbikes, can this be good ?

 

[jrkitching]

It’s a sealed system for gasses how can liquid be escaping and over a long time.

It's not a completely sealed system - it can't be, or you'd get a partial vacuum in the tank as the fuel was consumed. It will also be capable of venting any excess pressure which might build up when the car is standing outside on a hot sunny day, and additionally must be able to safely depressurise in the event of a vehicle fire.

I've not studied the detailed design of Fiat's system, but I'd expect there'll be a one-way valve to allow air in as the tank empties, a pressure release valve to limit overpressure, and an activated charcoal canister through which any vented gases must pass to remove at least some of the fuel vapour. Overfill it, and the excess fuel may find its way into places it's not meant to be.

 

[koalar]

It's not a completely sealed system - it can't be, or you'd get a partial vacuum in the tank as the fuel was consumed. It will also be capable of venting any excess pressure which might build up when the car is standing outside on a hot sunny day, and additionally must be able to safely depressurise in the event of a vehicle fire.

I've not studied the detailed design of Fiat's system, but I'd expect there'll be a one-way valve to allow air in as the tank empties, a pressure release valve to limit overpressure, and an activated charcoal canister through which any vented gases must pass to remove at least some of the fuel vapour. Overfill it, and the excess fuel may find its way into places it's not meant to be.

The pressure relief is built into the petrol cap

The evap it controlled by two separate valves nothing should leave the system until the solenoid at the other end opens and the fumes are burnt

 

[jrkitching]

Leaking petrol especially near a tyre on wet roads or for following motorbikes, can this be good ?

It's particularly serious for motorcycles and could cause a fatal accident.

 

[jrkitching]

The pressure relief is built into the petrol cap

The valve in the fuel cap isn't a pressure relief valve; it's a one-way valve to allow air into the system as the tank empties. If it's working correctly, nothing should vent out from it.

The whole point of the EVAP control system is to enable the system to dump excess pressure without allowing fuel vapour into the atmosphere.

 

[koalar]

You can read the full explanation of the system here

1080E EVAPORATION CONTROL SYSTEM - Fiat - PANDA - eLearn - 4CarData

 

[koalar]

The valve in the fuel cap isn't a pressure relief valve; it's a one-way valve to allow air into the system as the tank empties.

It’s both

• it discharges to the outside any surplus pressure which is created inside the tank (safety function); the pressure acts on the plate (2) and, overcoming the load of the spring (1), allows the surplus vapours to be discharged to the outside.

 

[koalar]

In all the time I had Pandas I have never known anyone have fuel leak from the system

If overfilled on the old system it use to kill the solenoid on the inlet manifold and put the engine check light on

Which may be why it was changed !

 

[jrkitching]

You can read the full explanation of the system here

Thanks; that's a most useful link.

So, looking at the diagram and the OP's photo of the EVAP components, it would appear that if you fill it to the point where fuel is at the top of the filler pipe, the fuel level will be above the level of the EVAP system and could find its way past the valves and seals into any/all of those pipes & tubes. What happens then is anyone's guess, particularly with E10 fuel given its propensity for swelling seals.

As your link describes, the EVAP components are deliberately placed above the level of the fuel tank: "In particular, even with tank (1) full, the two float valves (3) remain open because they are situated higher than the vent pipe. They therefore always allow fuel vapours to reach separator (2) and prevent fuel from emerging".

If you fill it to the point where fuel reaches the filler neck, the whole EVAP system could fill with fuel and all of that goes out the window.

 

[koalar]

Never really looked to much into the evap system as it just appears to work for hundreds of thousands of miles.

Thing like this “unusual” case are good.

Very few people brim fill But a few do to check MPG so I can’t see this being a design feature of over filling

With the cost of fuel it’s probably worth investigating more fully. I will wait to hear what other think.

Looks like on your original photo the blue pipes touch the black filler, Are we sure it started at the blue pipe.

 

[koalar]

If you fill it to the point where fuel reaches the filler neck, all of that goes out the window.

the float valve on the separator is shut though

Or am I missing something obvious

 

[jrkitching]

the float valve on the separator is shut though

Or am I missing something obvious

Looking at your diagram, it would appear the float valves are at the top of the tank, not in the separator. I'm trying to visualise how that diagram looks when fuel is up to the top of the filler pipe; would that cause the float valves (which are normally open) to shut?

This a most interesting discussion, but I've just been summoned to go shopping; I'll be back later!

 

[koalar]

Looking at your diagram, it would appear the float valves are at the top of the tank, not in the separator. I'm trying to visualise how that diagram looks when fuel is up to the top of the filler pipe; would that cause the float valves (which are normally open) to shut?

This a most interesting discussion, but I've just been summoned to go shopping; I'll be back later!

I couldn’t work out why the need for
So much complications

If you had the whole system in front of you would probably have helped

However it the first I have ever heard of leaking petrol

We have had rat damage

We have had damaged filler neck due to chafing

Seeing as we have some members that top of the tanks to test MPG and they haven’t noticed anything

I still of the mind something isn’t quite right

 

[koalar]

Dam missed the 15 minute editing window
The chaffing one was caused by a previous owner fitting coil overs and they were rubbing against the return pipe which subsequently holed.

So unlikely