A fuel pump must always be primed after installation or if the fuel system was drained or disturbed. This will help get fuel to the pump and into the lines before starting up, which ensure no air pockets end up causing some hard starts or engine misfires. For the most part, a fuel pump priming is routine chore and accomplished without any rarefied tools.
First off, electric fuel pumps (the most common type on a modern day vehicle) should be cycled with the key on without starting the engine. When you just turn your ignition key to first position (before cranking engine) it will activate fuel pump for few seconds (this is built-in feature, fuel pumps work by pressure not volume). Wait a couple of seconds, turn the key off and repeat three or four times to adequately prime the fuel system pump. Electric — makes certain the fuel is drawn from the gas tank to the lines and it is all set for combustion.
On vehicles that are so equipped (read: mechanical fuel pump-equipped), priming is a little more involved. With mechanical pumps requiring movement of the engine to operate, they needed priming and that was accomplished by either cranking the engine via the ignition or (much helping) using a ratchet on the crankshaft pulley. This procedure can be lengthy, as it is a AIr-motive regulator; therefore slower than electric pumps to fill the lines with fuel.
In each case, it is imperative to verify fuel pressure after priming with a fuel pressure gauge to ensure the pump has achieved its required operating range of approximately 35–65 psi for gasoline engines. If the engine produces low pressure after priming, then there might be a problem in the pump, lines or fuel filter.
When you forget to prime a fuel pump, it can create airlocks in the fuel lines, causing rough idling or stalling, or even preventing the engine from starting. That 12% of the fuel-system linked vehicle breakdowns are down to a simple failure in delivering gas, usually due to starved pumps or air pockets, per an AAA report from earlier in 2020.
Pay attention paying to maintenance, said Elon Musk, adding "The minutest thing can have repercussions to performance if not done properly." This principle speaks to the idea of having a fuel pump properly primed, for if not aligned in the proper plane realting to engine efficiency and supply.
Be sure to check us out over at Fuel Pump Source, where we house our full range of options for both fuel pumps and Bare Engines and offer further advice on how to maintain a healthy fuel system.