I am experiencing a problem with my peu 306 dturbo. it starts fine when cold but when i switch off engine and come to start it again it wont start easily unless i fully depress the accelerator! i can even see small bubbles coming out from the filter and into the injection pump. i tried a new priming pump stiil the same, eliminated the filter and improved a bit.does the injection pump have something to do? it works fine without any misfiring the only problem is that once started and switched off it needs a lot of cranking! any help? thanks