The 24-valve ISB engine will start & run even without a lift pump -- you definitely should not run it that way, but engine not starting can mean crankshaft position sensor failure (Code 1690 or 336 indicates a CPS signal issue) or VP44 injector pump failure & you may or may not get a code(s) indicating that. I've experienced both problems on my '98.5 truck.
The VP44 (1998.5 thru 2001 models) failure is most often in the computer portion & the only way to resolve the issue is to get a Frieghtliner upgrade pump with the "heavy duty" computer to handle heat & vibration the stock pump can't take -- sooner or later the soldered connections fail. I recently got the upgraded VP44 with a NEW Frieghtliner computer, after 3 stock pump failures, the original just out of warranty (dealer covered it anyway) & 2 rebuilt stock pumps, the 2nd of which didn't last 7 months.
