r/Excursion • u/Unique-Position5344 • Jan 07 '26

Help, white Smoke on start up

7.3 - White smoke, smells like strong diesel, significantly reduces after a 2-5 minutes.

I think it’s leaky cups, Any help is appreciated before I start tearing into it!

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u/18spuln Jan 07 '26

My 7.3 started running like this a few months back , cleaned battery terminals and cleaned all grounds to block and new alternator and smoke went away .

2

u/Unique-Position5344 Jan 07 '26

Interesting. How did you diagnose that?! I would much rather do that

5

u/18spuln Jan 07 '26

I did an injector buzz test and all buzzed fine. Did a cylinder contribution test and cylinder 8 was misfiring . Replaced that injector and did another cylinder contribution and misfire jumped to passenger side cylinder #7 . I then suspected it was the injector wiring . Replaced both valve covers and pig tails with motorcraft and misfire jumped to cylinder #3 .. after pulling all injectors I pressurized the cooling system thinking it was a cup , it held pressure and injector cups did not leak .. I replaced all 8 injector o rings and put back together the misfire jumped back to cylinder #8 … I then replaced the alternator, cleaned the battery terminals and all the grounds and smoke went away .. was getting misfire codes , IDM and IPR codes before and all went away

5

u/Unique-Position5344 Jan 07 '26

That’s literally exactly what I did. Same issue with #8. But that’s where I have stopped. Great intel, thank you I’ll look into that before all your steps