The fuel pump of a 1990 Honda Accord is located underneath the rear seats. There is a circular service panel that allows a user to easily replace and maintain the fuel pump without dropping the gas tank.
The fuel pump is mounted on top and inside the fuel tank. Look for an access panel above the fuel pump inside the vehicle. If there is no access panel then you will have to remove the fuel tank in order to access the fuel pump and remove it.
I inquired here about the location of the fuel filter on my 2001 Accord Lx. The answer I got was that it was in the fuel tank and that there was no need to replace it. I don't know if that would be the same for your car. Try calling a Honda dealer's service shop.
Replace the fuel filter. If the pump continues to shut down after 3 hours of running, replace the pump. You are in luck. There is an access panel in the trunk on your Honda. You do not have to remove the fuel tank to replace the pump.