Probably has a Riello burner, this one?
Don't turn any adjustment screw on the pump.....!
There will be a blanked off port on the side of the pump marked 'P'?
Undo this a fraction to allow air to bleed out of the pump when the burner is trying to start.
John
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local