1998 Chevrolet Truck engine cutting off

Hello to all I have a 1998 gmc van that runs grate except out of the blue it will cut off in about 10 to 15 min and I notice the fuel gage would max out when this happen and will half to sit up over night before it will start back up. I have plug in my car md and all I get is an error oh yes and the fuel pump come on and runs for about 3 second every time the switch in turn on. And there is a box underneath the hood over to the right there are pluges on this box that I un pluge all of them one at a time and sprayed them with wd 40 sense it is nun conductive it dose a good jub for cleaning contacts and also the fuse & relay box. I works on tv's I am in the electronics field. Thanks you for your help William