New Eco 7 Cylinder - spluttering/air in system?

[Goose0211]

We've just had a new Economy 7 cylinder put in and after 3 or 4 days we still seems to get spluttering out of the taps as thought there is air in the system

Basic setup as follows - apologies for poor terminology as i'm not a plumber! Cold water tank in loft of bungalow feeds into the hot water cylinder which then runs through a hot water pump (as we have V poor pressure) and then to the hot taps. There is a pipe going straight up from the cylinder - I assume a vent?

Setup of the cylinder is 'normal' - cold inlet at the bottom from the loft, hot out the top through a 'valve' connected to the 'vent'

In the mornings, when we turn the hot tap on, the pump doesn't kick in or does kicks in but appears to be running dry as though its not pulling any water through and we resolve by turning off the pump and then on again - only seems to happen in the morning after its been unused for 8-10 hours. The spluttering from the hot tap is random and happens on and off during the day.

The plumber that installed it is away so getting some advice and thoughts before he can come back!

Thanks all.

 

[Maryplumb]

Is the pump new? Where is it located?
It should be on the floor next to the cylinder. It's important for it not to run dry or it will fail. If it is not working correctly you should leave it switched off until your installer returns.
What was the reason for the cylinder being replaced?
A picture would be helpful.