Mjit Posted May 5, 2015 Report Share Posted May 5, 2015 Hi, Was away in my Spitfire over the bank holiday and had an intermittet missfire at low (sub 3k) RPM for the first part of the journey. This continued until I stopped for fuel and filled the tank. After that it ran perfectly, as it did at the start of the return journey. After a while the intermitten missfire came back...until I refilled again. My current thinking is the fuel pump's getting past it's best. Full tank it's fine as there's a head of fuel forcing its way to the carbs and at higher RPM the pumps making enough pressure to keep up with demand. At low RPM and a lower tank it's struggling to cope though. Not had a chance to check things out yet but does that sound plausable? Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 5, 2015 Report Share Posted May 5, 2015 sounds a good plan think youre on the right track. but make sure the tank is breathing ok Pete Link to comment Share on other sites More sharing options...
dougbgt6 Posted May 5, 2015 Report Share Posted May 5, 2015 Having messed around with my fuel line I don't think there's a lot of difference in pressure between a nearly empty or full tank. Its mainly down to the pump pulling the fuel from the tank. I would check your tank is vented properly if the air can't get in the pump is going to have a problem with an increasing vacuum in the tank. So as you say, on a long run getting towards an empty tank the pump will struggle. Link to comment Share on other sites More sharing options...
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