Hello all, 1st post.

I bought a 2nd hand vectra diesel in november last year. Had an engine service, new battery and glow plugs to get me through winter. Always started great, until the outside temp increased in March (above 13c). It can take a while to turn the engine over when the car has been stood still for over 12 hours or so. Turns out its a fuel issue, i dont know a great deal about motors but there has been a pump system fitted along the fuel pipe i presume, situated under the bonnet at the top of the engine(under the wipers) which includes a manual bulb type pump. a mobile mechanic told me to manually pump this to prime the diesel to the engine, which works to an extent. so decided to drop it in with my regular mechanic who suggests its the fuel pump drawing in air and its too expensive to repair on an old car. im wondering a) why was this not an issue on cold starts ? b) why would it draw the air in when parked up/switched off ? (there are no issues when the car is running, its never cut out once started). i have also noticed over the past couple of days that if i park the car either "bonnet down" on a bit of a hill or on a kerb with the passenger side raised it starts 1st time without priming (weird or coincidnce). I hope someone can help with my query, thanks in advance, Andy