how do i prime the fuel system on a 1999 honda accord.I just replaced the fuel lines

It should eventually start. You could crack open a line up on the intake, turn the key to on until you see fuel, that would save a lot of cranking.

will the fuel pump only run shortly at key on? so you mean cracking the hard line on the fire wall?

Yes. Then the fuel pump will push the fuel up and the air out of the lines. The rest of the air in the system will purge out threw the injectors.

1990 Accord is electronically fuel injected NO need for priming...if you cycled the key turned it on and off.. 2-3 times max it should have full fuel pressure, there is another issue if it doesn't. The question is WHY did you change the fuel lines?

Jeff, you replaced all fuel lines send and return the complete circuit OK, along with the fuel filter? '99 Accord. The normal 2-second fuel pump run ( turning the key to ON) is only sufficient to pressurize the fuel rail if (you just changed the filter, and the leaking lines etc.) then it can take a multiply ON/OFF cycles of the key before the rail fills up and the injectors get gas under pressure. listen as you turn the key ON/OFF does the pump energize? don't crank the engine over just, key ON/OFF keep doing 10-12 times if it still won't start connect at the fuel rail to check fuel pressure 38-46psi