Technical Starting problems

[Merlin 1106]

Hi I have Ducato multijet100 2.2 diesel van. It's 2006 and converted to a campervan. Sometimes it won't start until I remove the fuel filler cap when I hear a small whoosh sound like it's releasing air from the tank. It mostly starts after doing this and it happens when it's cold or warm

 

[Communicator]

The fuel cap on my earlier x244 is designed to vent for either positive or negative pressures. I think that yours will be similar, perhaps yours is failing to admit air when required.

 

[Communicator]

@Merlin 1106,

Is your fuel filler OEM, or modified by the converter? If modified, the this thread on Motorhome Facts may be interesting.