1994 Nissan Pathfinder Intermitent problems with starting

I am puzzled and so are the mechanics that have been working on my wifes Nissan. We had it towed to them because it would not start. I could crank it over but it would not fire up. They ran diagnostics on it and everything showed good and when they went to start it of course it started right up. They kept it until it did it again but they were able to start it by pumping the gas. Once it starts it runs fine and you can drive it all day. I had them replace the fuel pump because the pressure was erratic but it still did it afterwords so they replaced the coil and cleaned the throttle plate and checked all sensors. It's not missing out or anything and the plugs and cables check out. My wife drove it to work all week with a few minor hick ups but it always started. She got stranded for about 30 minutes because it wouldn't start but finally it did. This is becoming very frustrating and expensive. I would appreciate any help I can get at this point. Personally, I think it is a sensor or something that controls the idle and the air to gas mixture. Please help if you can.

Thanks,
fondu