I'm having a crank hard start in the morning on my 6.0, outside temp is about 80deg. After it starts about 10 cranks it run rough for a few minutes then it runs fine. I'm getting 48 volts key on engine of them when I start the engine it drop to 16 volts after driving for few minutes volts go up to 20-30 volts.my question is should the voltage stay above 25 volts when driving?

 

The lowest your voltage should ever get is 45, your ficm is toast. You need to have your ficm repaired ASAP. Check out Ed at ficmrepair.com he is a site sponsor and has great customer service. Lots of guys on here running his if ficms and are very satisfied

 

Your FICM is shot anything under 45 volts it needs replacing or repair. It should never go below 45 volts. One questions how are your batteries?

 

Agreed FICM is shot, but the condition of your batteries and alternator plays a pivotal role in the FICM's destruction.

-Are your batteries topped off? Chances are your batteries are low on distilled water and they just need to be topped off. They just need to be filled to the bottom of the fill hole on each cell and you're good to go. Once you do this, put them on a charger until charged, then reinstall on your truck.

-If that doesn't help, After a cold soak overnight (minimum 12 hours) pull the batteries and test them at Autozone or an auto parts store. If you drive over to the store and then have them test, the surface charge the alternator leaves is enough to cover up a bad battery. Ask me how I now...

-Look at your battery connections. Make sure the battery posts are clean and the connectors are good n tight. Are the terminal connectors corroded and about to fall apart? O'reilly's house brand Super Start makes a wiring kit designed for the 7.3, but works on the 6.0 with some modification.

http://m.oreillyauto.com/mt/www.orei...?keyword=04357

It requires a splice in the middle as it's just slightly too short and don't replace the cable down to the starter. It's already 2/0, so all you'll need to do it butt the cables and you're good to go.

-Make sure your alternator is putting out the voltage it's supposed to. My factory alternator would only put out 13.5 volts max. After several replacement alternators, I took it to a rebuilder, they went through it, and the problem was the regulator. It had a low set point at 13.5 volts, so it was replaced with one that had 14.5 volts max and my charging system is up to par now. If you also have the small case 110 amp alternator for some reason, consider upgrading to the large case 140 amp alternator. It might not seem like much, but it made a world of difference on my truck.

While you do need your FICM repaired, check what I've suggested so you don't go through this again.

 

The batteries tested good and all terminals are clean and tight.my question is that if I'm getting 48 volts koeo and as soon as I start the engine voltage drops below 25 volts. And your saying it should always be at around 48 volts even with engine running? I also checked charging system and all checked out good.

 

It should be 47-48.5 volts KOEO, KOER, and while cranking.

 

Awesome, thank you for your insight on this matter, sounds like it's the ficm. I just wanted to make sure it needed before replacing.now do you recommend the dealer or aftermarket?

 

Aftermarket, in this case does it better than the dealer with a better warranty.

www.ficmrepair.com