My "87 Pathfinder has run great for a couple years since buying it. Three weeks ago, it began getting harder to start. It took more cranks to fire up. then eventually it just stopped starting. Ignition sparks are okay. So I decided to pour a small amount of gas directly into the intake. After a few rotations, it fires up, and runs perfectly. I shut it down and restart, no problem. If I let it sit a couple hours, it won't start. It's as if the pump has lost prime, and won't transport fuel. So I pour a little more fuel in the intake and it's running again. Could it be the fuel pump? The filter was just replaced. I got it running again and drove it to the neighborhood mechanic to let him worry about it, but thought someone here could give me some insight. Any ideas?