1999 GMC Jimmy will not start

1999 GMC Jimmy 6 cyl Four Wheel Drive Automatic

my car was running fine, until one morning I went out to the car, and it would not start. It turns over, but it was not getting any fuel. Under the car on the drivers side, there is a plastic panel, and someone told me to try pounding on it, and then try to start again, and this worked for awhile to start the car. I was wondering if this could possibly be a faulty inertia switch, and if so, is there a way to test it.