Technical Help with dash warning light

[surfstar]

Hi, I have a fiat Ducato 1989 2.5D motorhome. I lost the fuel cap some weeks ago whilst touring and have made do sticking an old rag inside until I get one. This weekend we went away and a dash light came up that raised some concern. It is a water bottle with fluid in and in my German instruction manual it says it is condensation in the fuel tank and it should burn off after 2 seconds. Well it hasnt gone over for a few days and im concerned driving it will cause damage. Can anyone help. Im thinking my lack of fuel cap may have something to do with it.

Thanks

 

[wayfarer]

This indicates water in the fuel filter. Drain or replace fuel filter. The fault light may have to be reset, but try this: Turn on ignition and start van, turn off ignition, turn on ignition but do not start, leave ignition on for about 60 secs. Turn off and restart. This works for some fault lights.
PS. Buy a fuel cap.