Hi Dave,
Many thanks for your comments.
I forgot to say that the engine is a 2 liter 130hp.
The strange thing about it is that the engine has been running on a test bench perfectly!
On my bench I have the circuit exactly how it is on the diagram Dave posted.
The fuel tank in car is slightly different: the oil filter and console is lower and it has the supposed outlet to feed the oil pump under the oil filter. On the face downward, at the lowest point, it has another connection to receive the line coming from the engine cooler...
Very similar to this:
