1985 F250 - Alternator Issues???

It doesn't take long to go from you think you know what your doing to realizing you may not be that guy?

I have been working on my 1985 F250, 460, 7.5L with electronic fuel pumps, dual tanks, and all the California emissions a guy could ever dream of.  I successfully changed out the double tanks, sending units, pumps, fuel lines, fuel pressure regulator, valve selector and fuel relay to get it running like a top after sitting for about 10 years.  I was in celebration mode and thought I would get all the interior lighting working and needed a few fuses.  Unfortunately on that trip I was stranded as it would not start for the trip home.  With a boost on the battery it fired right up and I took it back to the barn to diagnose.

I determined that I would change the external voltage regulator and see if that did the trick.  It still would not charge the battery so I then also changed the alternator with a remanufactured 1G exactly like what was on it before.  Still no charge to the battery. I then thought the connector to the voltage regulator needed to be replaced as it was of questionable character with a VERY rusted and nasty connection to the "A" terminal.  I cut the old connector off and rewired a new one making very sure that my wiring was exactly as before.  I started the truck up and it did not run well and was squealing like a pig!  I turned the key off and the truck continued to run, removed the battery terminal and suddenly it started running very good as it had before this whole fiasco.  To stop the engine I had to disconnect the voltage regulator connector.  

I spent another 4 or 5 hours tracing wires and ensuring the alternator and regulator are all wired properly.  

I have 12v all the time on the A terminal of the voltage regulator connector
I have 12v with the key on at the S terminal of the voltage regulator connector
I have 0v with the truck running at the F terminal of the voltage regulator connector (I did verify the wire is in good working order, no resistance and was wired properly to the alternator, "Field"Terminal)

From the alternator the "Bat" wire is ran and connected to the positive side of the starter solenoid.

When the voltage regulator is not plugged in the truck runs great, but whenever it is plugged in I have the problems as described. I'm really at a loss on this and haven't found my exact problems anywhere online. Hopefully someone out there can help!

Thanks!

I don't know whether you have gauges or and idiot light, but here is a link to the idiot light system:
https://www.garysgaragemahal.com/charge--power-distribution-gas.html

Here is with the ammeter:
https://www.garysgaragemahal.com/charge--power-distribution-gas.html

They may both take you to the same place, ammeter is the second set of diagrams.

The fact that you had to disconnect the voltage regulator connector makes me wonder if your ignition switch could be the problem as they have been known to come apart.

Good luck with it.

TeamCope wrote

 I turned the key off and the truck continued to run, removed the battery terminal and suddenly it started running very good as it had before this whole fiasco.

Concur with Bill. Ignition switch position should be checked and/or replaced first and then you can report what happens next. Unless you have a diesel that can runaway, your truck shouldn't run with ignition key off.

Sorry I tried to remember to post all of the options! It does have an ammeter setup and it is a gasser. Thanks for the direction, I’ll look into the ignition switch and report back. Much appreciated!

😳

Dunning-Kreuger Is obviously a thing, but the first step to recovery is admitting you have a problem.

You have some good clues and a direction from Bill

Finally got back to it.  I replaced the ignition switch.  When taking the old one off it fell apart in my hand.  Once the new one was installed it started charging the battery and all seemed well until it wasn't.  As I chase it further, it begins to run rough and intermittently dies as though it is starved for fuel.  When the voltage regulator is unplugged it runs like a top so I don't believe it is a motor or fuel problem (also I have already replaced, tanks, sending units, wiring, hoses, tank selector valve and fuel pressure regulator), however, when I have the voltage regulator sometimes it runs and other times it dies.  I have replaced the fuel control module and the plugs were VERY corroded.  I attempted to clean them up but the issue still persists.  I am thinking I should change the wiring to the fuel control module or trace the wiring to see what else it could be.  I'm open to any suggestions someone might have....

Thanks!

I'm going to suggest that you may have low hot oil pressure, or a bad safety switch.

Try jumpering the oil pressure cut-off behind the EGR and see if the problem persists.