The Landy cut out the other day and it would appear that the in-line filter to the carb was practically empty of fuel. It would run for a few seconds if I used the pump handle to refill the filter but then cut out again. So bought a repair kit for the mechanical lift pump and at the second attempt bought the right parts. I've replaced the Diaphragm but cannot replace the valves as they are crimped into the head. Refitted the pump but now absolutley nothing. Cannot fill the sediment bowl through either the pump handle or turning the engine over. Checked as best I can for air leaks or blocked vent to tank and doesnt seem to be the problem. Do I need to buy a new pump; I'm reading the new replacement unit is not as good as the originals. Any tips or hints gratefully accepted.

The mechanical pumps are usually good, I have only used diesel ones and the Britpart one I bought was awkward to fit but worked. For your petrol engine consider an electric pump, easy to fit and cost effective.

You may find it easier to prime if you disconnect at the carb or inline filter and pump up to a catch bottle. If the carb is full the needle valve won't let you pump any more in...

Was the old diaphragm split?
The pump could be on the high spot of cam flick engine on starter motor and try again.
You should just need to loosen a union and pump till it leaks .
Could also be blocked filter on fuel pick up in tank.