When iddling my fuel pressure doubled from 40 psi to 80 ( on dash meter ). Checked all hoses etc .but coul not find anything.
I replaced the regulator and set the fuel pressure to 40 psi. But, after driving a while the fuel pressure increased again when standing still at traffic lights etc...
Where to search ?

Has the regulator got a manifold vacuum connection ?

The fuel rail should be about 3bar above inlet manifold pressure.

For most injection systems with the regulator connected to manifold vacuum.

With the engine off but pump on the fuel rail pressure should be about 3 bar.
At idle the fuel rail pressure should l be closer to 2 bar than 3,
At full throttle the pressure should increase to close to 3 bar.


However a lot of tintops built in the last ten years have the pump, regulator and return line within the fuel tank ---on the these cars the regulator is not connected to manifold vacuum and the fuel pressure should run at a pretty constant 3bar relative to atmospheric.

thank you for the reply. seems like fuel pressure is OK now, but have to do some more testing. the vacuum connection will not be connected, to keep the pressure constant.