Fuel pump harness

1998 Chevy astro 125522 mi 4.3 I started have a problem starting my car yesterday went to the zone they scanned it and said the o2 sensor was shot and the egr valve was stuck so I changed the o2 sensor lower bank removed the egr cleaned it put everything together and the van still didn't start I didn't hear the fuel pump so went under the car to check for power as soon as I moved the harness to the fuel sending unit to find the gray wire I heard some nose in the tank so I gave it a shot turned the key and it started right up after it sits for awhile it wont start I move the harness again and the car starts up fine question is it possible to change the harness or does the whole sending unit need to be replaced