I have a VN One Tonner with the same problem, additionally once in a while it would stop while driving. RACQ told we it was the fuel pump, after investigating we found it was the five pin plug on top of the pump assembly poor neg contact. We bypassed the plug negative line creating an new negative . This worked for about six months then the tonner stopped again.
Off to Holden I went to buy a new plastic assembly, only to find my tonner was one of a few to have a "Special" assembly that had a five pin plug on top, no longer made. Inquired at all the usual places plus some obscure ones, no go or pump cost more than car. We ended up completely bypassed the plug to the pump with both pos and neg wiring line as well earthing it back inside the Cab. All works, NOW my fuel gauge also works. Possibly the problem has always been poor contacts to sender.