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water in diesel warning light


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Hi hopefully someone can help a technophobe with some common sense advice.

We've just returned from a 1400 mile trip which went brilliantly until on the second last day a warning light appeared on the dash of our 2008 Fiat Ducato 2.2.

Never having seen this light I stopped and looked up the handbook which identified it as "water in diesel filter".


The tank was half full and it was 200 miles since we topped up with fuel (at a supermarket) and the van had been behaving itself well rocketing up the M5 and other than the warning light there was no evidence of a problem, no stuttering or loss of power.

Not being at all technical we did as advised in the handbook, stopped and called recovery.


Within an hour we had a new filter and were on our way again, this time with the knowledge that even someone as useless as I could drain the fuel filter.


100 miles later the light came on again, this time I drained the filter and set off again, light off, topped up fuel, light comes on again roughly about another 100 miles, decide "sod it" its pouring rain, its late, van still going well we'll just keep going as we're only 50 miles from home - about 20 miles later light goes out!


I've had varying advice from local "experts" from I need to drain the diesel tank, to I have a duff sensor.

Before going to a garage I thought, well I'm not the only one with a 2.2 Ducato so someone else out there might have come across this.


Any advice welcome, as we're about to set off on the second half of our 2011venture.



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Does the handbook really just say stop and call Recovery as soon as that light comes on?




Nothing about "bleed diesel filter"?..........'cos surely that's what they aught to advise........and show you how to do it somewhere else in the book, 'cos it's a very straightforward thing to do (always assuming the setup on your Fiat is the same as on other diesel engined cars and vans)...

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Handbook only says in the warning light section "contact Fiat dealership to have system relieved".


Can't see anything else in the handbook .

Recovery guy showed me the screw at the bottom of the filter, said to drain the filter undo the screw and turn key to first position to push diesel through the filter.

How much needs to be bled off this way?

Sorry to be thick but not used to this level of hands on.

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If you've got significant quantities of water in the fuel tank and this is what's causing the warning-light to come on, then the fuel tank (and possibly the complete fuelling system) will need to be drained/purged as soon as possible.


If it's just an electronics fault causing a false warning, then this will need to be professionally diagnosed and corrected.


As the warning light has come on and then gone off a couple of times since the filter was changed/drained, and the vehicle's performance is apparently OK, I'd be tempted to think it's a sensor problem rather than the fuel, but, either way, it's not something to ignore as diesel fuel contaminated with water can have a disastrous effect on modern motors.

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I'd suggest going out to the van today,, after it has been stood overnight, and thus any water in the filter should have fallen to the bottom as it is denser than diesel; and bleeding some more fuel from the filter....by partially undoing the nut/screw at the bottom of it, as the RAC guy showed you....into a jam jar.


(If you've forgotten how to do it, just go to utube and watch some videos on "how to bleed fuel filter")




Leave that to settle for a few hours, then have a good look to see if there are any "blobs" of water swilling around in the bottom of the jam jar.

If so, you're still getting water coming through with the diesel from your fuel tank:

Either because you were very unlucky and drew some diesel from a garage pump when they'd just refilled the bulk tank, which mixes everything already in that tank up for a while; or because of the action of condensation over time from the moist air that gets into your van diesel tank.


If there is water in the bottom of your "test" bleedoff jam jar, then it's not a major problem....indeed it shows that the fuel filter is doing exactly what it should. You could just keep bleeding the filter each time the warning light comes on.


If there isn't any water in your jam jar, yet your warning light is still coming on, then it's perhaps more likely that either you have a faulty sensor, or even (MUCH less likely, but not impossible) air is somehow getting into your fuel supply line, or there's a partial blockage somewhere along it.

I say this 'cos from memory, and certainly on older diesel vehicles that I've played with, the sensor works on pressure. Some are fitted just before the filter and activate if pressure increases beyond a set point. Others are fitted downstream of the fuel filter and activate if fuel pressure drops below a certain point.



So, if there's no water in your jam jar....it sounds like you need to tootle along to a mechanic who is competent in dlesel fuel systems.

Remember that there is NO requirement to use a Fiat dealership whether in or out of warranty......and I'm guessing that any garage could sort you out as your fuel filter/sensor are NOT Fiat-specific, but are generic parts made by Bosch or someone else.


Hope this helps.



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Thanks folks, knew there would be good practical advice from the forum.

Bled some diesel this morning and there was a very small amount of water at the bottom of the sample. The filter is as you say doing its job as is the sensor.

Just need to keep an eye on it from now on but what a relief to know what to do.

My former work colleagues will never believe that I've (succesfully) used a screwdriver in anger as they spent their working lives keeping me away from anything mechanical.

I know I'm a bit of a worrier but a warning light coming on with 200 more miles of motorway to go knocks all rational thinking out of me.

Motorhoming is new to me and I've obviously a lot to learn, still thanks to you folks I can chalk up one less thing to worry about and put another "skill" under my belt.

Thanks again


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  • 2 weeks later...

It sounds as though you may have picked up some contaminated fuel. Although the filter should prevent it, the slightest trace of contamination getting past has the potential to destroy the common rail fuel injection on your vehicle. Think £1000+


My advice is to immediatly bite the bullet and have the tank drained, a new filter and the fuel system flushed through with clean fuel.

say £ 50 loss of fuel + a couple of hours labour . Dont put it off.

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