7.3 broke down
 

My 95 7.3 quit running going down the road. No warning just shut off. Engine cranks fast but will not fire. Got it to start the next morning but just ran for a few seconds and then sounded like a limp mode and then shut off. Checked fuel filter, replaced crank sensor, and does not show a code. Puzzled.

My first question would be ar you sure it is not out of fuel?

Really??? Everyone should know I am a mechanic and have exhausted all easy fixes. Like tach sender replaced, fuel filter clean and full of fuel. Oil full and clean and has oil pressure when I can get it to fire for a few seconds.:confused:

Fuel pressure and volume should always be checked to rule out delivery issues.
Early 7.3 had IDM problems usually due to water intrusion/ corrosion. Since it seems to start and run for a few seconds should/ would rule out fuel bowl heater shorts causing a dead PCM fuse.
HPOP could be cause, since the 7.3 is very picky on cranking speeds, fuel pressure, and a start up HPOP pressure.

Check engine light ON when it runs? How many miles on the truck? Any repair history? injector o rings replaced, HPOP? Was fairly common for a Low cranking oil pressure to cause hard/ no starts.

A scan tool is a great help to look at pressure to also rule out insufficient pressure during crank. As well as looking at the other PIDS to make sure their spec, as well as any active codes present for a direction or cause. UVC harness failures were also a big issue, as were glow plugs... Neither of which should have been a problem for it shutting down at speed, but always something check will under the hood and as part of a start diagnosis.. Looking at the valve cover connectors, usually seen as swollen or burned plastic..

All Fuses are ok. 271,650 miles original owner. Have replaced valve cover harnesses two years ago.Check engine light came on when it shut down the first time, but has not come on again after three restarts. No major engine repair. Was running great until that day. No warning just shut down. Had it do that before when the tach sensor went out two years ago so I replaced it first being it is only $20.00 and easy to do. Have a friend with cat who is going to bring his scanner by. He thinks it may be fuel pressure or high oil pressure switch behind high pressure oil pump.

Thanks for the positive input.

Scan tool would be a huge help.
He'll be able to check IPR, IPC values as well as HPOP Psi. Might try and unplug the ICP and see if there's any improvement for a start. IPR may be stuck/ plugged, but generally wouldn't have caused a complete stall, and a no start. More so since you claimed it was running fine prior.

In Functional tests, he should be able to Buzz Test the injectors ( IDM -PCM) to check function.
Any stored or pending codes certainly would help in a direction.

Closing in on 300k the possibilities are many. Good spec fuel pressure/volume certainly could cause a quick fail. IDM, and HPOP insufiency as well. Being it seems its trying to start, I'd lean towards fuel and oil psi delivery..

Problem found. High fuel pressure. Trailered it to Browns Diesel in Riverdale for all repairs.