99 7.3 Won't start

[Tail_Gunner]

On my way I noticed the truck loosing power and I could barely do 50 mph with it floored.

I'd be checking fuel pressure too.
While it didn't get that bad, I was experiencing similar symptoms before I replaced the fuel pump. At idle the pressure was fine, but under a load on the road, it dropped off severly, down to about 10 psi.

 

[SMOKNZ]

Well tried the oil, I was 2 quarts low. Didn't work I bought 2 new batteries and will try them tomorrow. If that doesn't work I will investigate the under the valve cover harness. I was in there a year or so ago replacing all 8 glow plugs. I seem to remember an upgrade to the wiring harness, does anyone know where to get it?

Bill

 

[SMOKNZ]

Batteries replaced and same result, no start. Next step is fuel pressure and then I will check the wire harness.

ANyone have a link to the upgraded wire harness for under the valve covers?

Bill

 

[JMF350]

Any results yet? If not, check to see if it has an Intake Air Temp sensor (not sure on a 99). I was diagnosing an ambulance in the shop a while ago, that had the same cranking caracteristics as what you have. Kinda hit and miss, with thick black smoke. Got to checking and found the IAT sensor unplugged. Plugged it in, and more or less fired right up, maybe an extra 3-4 seconds of cranking, but has fired normally since. Hope this helps.