Hi Angus

Thanks for your reply.

The owner informed me today that the tandem pump had been changed, news to me. I got him to bring on the old one and I changed it back. Made no difference but I now know where the green substance came from, sealer on the pump.

I have no restrictions in the fuel lines and I get 1.5 litres flow from the electric pump.Deadheading the pump gives 7.5 bar. I'm not concerned about the tandem pump pressure as I believe if I sort out the low pressure side that will be ok.

This has the fuel filter with five screws on top, 4 connections. I have 4+bar on three and 1bar on the tank return. The filter head must have some type of pressure regulation, otherwise I beleive the fuel would just return to the tank.

My theory is, with the fuel lines reversed at the pump for some length of time, the filter head was damaged, so I will try to get a new one tomorrow.

Let you know how that goes.