Richardtr3a Posted June 27, 2021 Report Share Posted June 27, 2021 After replacing my fuel connection, stop to pump, it was impossible to hand prime the carbs. I has a specialist tuner on site and we ended up driving to the local filling station for fresh petrol. We filled the float chambers by hand with a small funnel, and it started immediately and ran well. Is it possible to get an air lock between the tank and the pump.? Thanks Richard & B Quote Link to post Share on other sites
mikej Posted June 27, 2021 Report Share Posted June 27, 2021 Air lock very possible, the mechanical pumps are transfer pumps with little "lift" ability. If it runs OK now then your Ewarts petrol tap has not failed, yet! MikeJ Quote Link to post Share on other sites
peter clarke Posted June 27, 2021 Report Share Posted June 27, 2021 The mechanical pump runs off the cam shaft and if the lobe for the pump is on the high point the priming lever will not work. Crank the motor over off the high point and the priming lever will then work. Quote Link to post Share on other sites
Ralph Whitaker Posted June 30, 2021 Report Share Posted June 30, 2021 On 6/27/2021 at 11:50 PM, peter clarke said: The mechanical pump runs off the cam shaft and if the lobe for the pump is on the high point the priming lever will not work. Crank the motor over off the high point and the priming lever will then work. Given that the tank is above the fuel pump I would think it would be almost self priming, hence the need for the Ewarts tap. I think Peter is right about the pump activating lever being "on cam" holding the pump down, it feels as if the lever is working but in reality it is not. Ralph Quote Link to post Share on other sites
ianc Posted June 30, 2021 Report Share Posted June 30, 2021 Yes, one can get an air lock - it happened to me when I had to take out my tank in order to "slosh" it in 1997. I put a couple of gallons of fuel into the tank, toggled the priming lever on the pump, but nothing happened. This is how I overcame the problem (see K3 in the Technicalities CD): I jammed a piece of rubber hose into a plastic funnel, then held the funnel tight into the tank's open filler. After my third breath into the hose, there was a burping from the depths - it was just the filter bowl filling rapidly! Ian Cornish Quote Link to post Share on other sites
Z320 Posted June 30, 2021 Report Share Posted June 30, 2021 The original fuel pump is a diaphragm pump with two anti reverse valves. This is why it can pump fuel AND air without problem. You can test this yourself when you have the pump in your hands the next time. With the petrol tank out or empty several times for different reasons I never had a problem to get the pump working again. I never did something special. Ciao, Marco Quote Link to post Share on other sites
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