When trying to 'assist' start a 7.3, it's a real good
idea to disable the glow system by pulling one of the connectors/terminals off the glow relay otherwise you can get amean 'flame back' through the intake.. Better yet to not even use ether on a 7.3.. A better way if 'absolutely necessary' for a assisted start is to soak a rag with gas (not dripping) and hold it firmly
in the intake pipe air stream as the engine is cranked.. A less violent alternative, but not recommended
Being your truck has close to 300k on the clock it could be a HPOP problem, or a high pressure oil bleed.. But,, when a 7.3 is started a few things need to happen (and must be checked) as part of the diagnostics..
1. First is a good healthy set of batteries so the engine can crank 'at least' 100RPM or the engine will not start since thePCM doesn't detect the CMP signal at less.. Without a CMP/PCM on line,, the injector driver module won't fire the injectors..
2. There must be good fuel pressure and volume, if the stats aren't known, it should be checked to ruleit out as a possibilityfor the no start , or more so for performance concerns under loads ect..
3. The HPOP (high pressure oil pump/system 'MUST'be able to produce 500lbs of oil pressure for the 'push' for the injection.
During a 7.3 diagnostic for a no start,, the first thing would be to look at the PIDS (Parameter Identification Display) or some call them parameter information with a diagnostic scanner.. It's a 'look into'the needed PCM system values input/outputs,,, like what PSI thehigh pressure oil is meeting, for example 500lbs for the startup, indicated cranking speed, an injector pulse present, IPR/IPC (injection pressure regulator/injection pressure control valuesand so on.. Reason for the long explanation is that without a scan tool for diagnosing a no start it's a little tough, although not impossible..
With close to 300k on the meter, it may be a good idea to check for spec HPOP oil pressures.. You can install/plumb a test gauge (500lbs or better) into the HPOP line at the head and read the PSI.. If you see 500lbs on a crank you should be ok there.. If the pressure is below spec., there's a few hose/plug combinations to test each head individual for injector oring problems as well as to help pinpoint banks 1-2ect.. Could be a IPR (pressure regulator) oring issue as well, or a IPR failure..
Fuel pressure can be checked at either head,, passenger/right head there is a 1/8 pipe plug inwards towards the valley up front between the water/fuel seperator and the head.. Left/drivers head is in the rear area of the head..
On the top portion of the HPOP reservoir, (under the front edge of the dress cover) there is a plug, remove the plug and make sure the engine oil is within 3/4-1" of the top..
The thing that is sketchy, is that it ran 'fine' correct? prior to the no start.. No running concerns?? Another thing I might check would be the PCM fuse,, if the fuel heater comes loose, it can short and will blow the PCM fuse but since the truck was running then died, probably not the cause but thought I'd throw that in as a check point since you cleaned the filter housing..
It's more of a 'rule out' the possible causes first, rather than guess what it is.. If your pretty sure the fuel pressure is good, the next check point would be the HPOP/system concidering your trucks mileage..
By spraying ether into the intake and the truck runs/starts for a short time doesn't eliminate fuel control problems as a far as electrical, since what its doing is running on the 'prime' fluid..