Water in fuel sensor

scarecrow · Post by **scarecrow** » Mon Aug 23, 2010 10:02 am

Not strictly about a bx but, I'm interested in a diesel xm which the owner says has the water in fuel light on and has started to stall a bit...

Would this be just a matter of replacing the filter (there's one on the pump, right)?

Could it be an indication of something more untoward - I mean, could there be mechanical issues causing water to get in to the fuel, or is this just a normal regular maintenance thing?

Thanks

Post by **mat_fenwick** » Mon Aug 23, 2010 10:41 am

It could be just down to a maintenance thing...BUT...if so why haven't they done the (very) simple job of draining the filter housing, and if they haven't done that basic maintenance then what else has been missed? Plus, if the water has now built up to a level which is causing running problems I would be wary of possible pump damage.

BX Bandit · Post by **BX Bandit** » Mon Aug 23, 2010 11:17 am

What vintage XM? Early ones were prone to HG failure which can be rectified by the later style head gasket made from bullet proof heavy armour! Not sure what the cut off date is between those with crap head gaskets and those with the gooduns. Possibly when the mk2 came in around \'94??

scarecrow · Post by **scarecrow** » Mon Aug 23, 2010 1:40 pm

This is the one http://cgi.ebay.co.uk/1991-CITROEN-XM-T ... mobiles_UK

Having contacted the seller he's confirmed it was the one being sold on ebay last week and that it's developed this fault since getting it home... Ph1 too

It all sounds a bit too suspect for me so I'll leave it - thanks for the advice.

Post by **Defender110** » Mon Aug 23, 2010 9:18 pm

Looks quite a nice example though and in answer to your original question the water sensor is in the bottom of the filter cartridge and indicates a build up of water in that filter. This is purely from the fuel tank supply and is not linked to any other mechanical part causing water to get into the fuel. It is however a sign of either very poor maintenance or the fuel cap being left open in the rain as this light never comes on when filters are changed at their correct intervals and althought the water ingress is not linked to any other mechanical parts water in the fuel can eventually cause damage to the injector pump and injectors.
I have to agree that selling so soon after buying is a little bit suspect though.

scarecrow · Post by **scarecrow** » Mon Aug 23, 2010 9:39 pm

I remember the petrol cap cover-flap was missing in one of the photos from the previous listing... Makes you wonder.

Sounds like a potential nightmare so I'll steer clear.

Thanks for the advice

electrokid · Post by **electrokid** » Mon Aug 23, 2010 11:09 pm

Get a bottle of 'Dry Fuel' and put it in the tank - it's basically alcohol - it mixes with both oil and water and the mixture just goes through the system and gets burnt taking the water with it.

Post by **Defender110** » Mon Aug 23, 2010 11:33 pm

Just dropping the fuel tank and emptying it would be a much better idea than letting the water through the injection pump and injectors and risking the water damage.

electrokid · Post by **electrokid** » Tue Aug 24, 2010 7:24 pm

The water dissolves in the alcohol and the alcohol mixes with the diesel - it doesn't affect the pump for the same reason that the sugar in your coffee doesn't scrape your throat on the way down

Post by **Defender110** » Tue Aug 24, 2010 8:08 pm

I don't have sugar in my coffee!

scarecrow · Post by **scarecrow** » Tue Aug 24, 2010 8:20 pm

electrokid wrote:The water dissolves in the alcohol and the alcohol mixes with the diesel - it doesn't affect the pump for the same reason that the sugar in your coffee doesn't scrape your throat on the way down

I'd never thought of water dissolving in other substances before - always the other way round. Is it defined by the ratio of one to the other?

electrokid · Post by **electrokid** » Tue Aug 24, 2010 11:12 pm

I don't have sugar in my coffee!

I had a feeling it was the wrong analogy when I wrote it

Is it defined by the ratio of one to the other?

To an extent - strictly speaking water forms an azeotrope with alcohols - see...
http://en.wikipedia.org/wiki/Azeotrope
If I was starting over I'd go into chemistry rather than engineering - there is so much still to be discovered - one of my chemistry books begins with a bit of very refreshing honesty - effectively it says that this book will tell you what we know and will highlight where there are errors we can't yet account for...

Anyway - back to alcohols... my favourite (usefulness and smell

) isopropyl alcohol or IPA - used to be available in pre-injection swabs (medical) - very useful for cleaning video recorder heads - mixed with small quantities of water still evaporates very quickly so wiping a surface with IPA will leave it bone dry. Grease and oils also dissolve in alcohols so the surface is dry and free of oils.

Don't use it neat for cleaning acrylic though (such as headlamp protectors) because it can de-stress the structure of the acrylic and you can end up with a crazed mess.

You can stick it in your fuel tank though (petrol or diesel - not sure about SVO or bio but I don't see why not) - the product called 'Dry Fuel' is mainly IPA. If you suspect water in the fuel use about twice as much IPA as the amount of water you suspect to be in there as a starting point.

RxBX · Post by **RxBX** » Wed Aug 25, 2010 1:09 am

scarecrow wrote:I remember the petrol cap cover-flap was missing in one of the photos from the previous listing... Makes you wonder.

Sounds like a potential nightmare so I'll steer clear.

Thanks for the advice

Previous E-BAY listing, complete with a fuel cap filler cover-flap

!

Also the XM model/type being referred to is a 2.1 SD Turbo, so the fuel will be DIESEL rather than petrol

But thank-you, for the info/update, which I've link into the THIS 'XM forum' thread (where this XM has previously been discussed) you may need to be a registered member to see that part of the forum !

.

Post by **docchevron** » Wed Aug 25, 2010 2:40 am

You dont have to be a registered member to see it, but I'm getting lost in all the links to this site, that site, back to this site, via E-bay and here again!

scarecrow · Post by **scarecrow** » Wed Aug 25, 2010 7:04 am

Yup - the xm club link doesn't throw any more light on this one, and I couldn't quite understand if the reference to a head gasket. problem was relevant.

Petrol flap/ diesel flap - I must have got confused with one of the other dodgy xm's being hawked on shit-bay that week. I haven't checked but now you mention it, yes, my bad. It does still appear to have water in fuel though.

I feel sorry for the new owner with this one. The chap selling it before slagged off bxs when I contacted him and the listing ended not long before the 24 hour non-withdrawal shit-bay ruling was due to apply (and I'd told him I was waiting until then before I'd consider viewing before making a bid). The gentleman informed (EDIT: <me>) of the problem when I asked if there were any mechanical faults - then when I passed on the information about the water in fuel issue and cleaning the filter, he mentioned that he'd tried to clean it but that there may now be an "airlock".