I have a 1991 f150 truck 4x4 with a v 8 engine. Engine size is 351.

My truck has been starting everytime since I got it last month. Then I went to go start it yesterday morning. It would start. I was getting power to the radio, headlights, and internia lights. So we change the fuse that was burned out. My dad got the truck to start two times. Then He let it sit for five minutes. Then the truck wouldn't start and was discharging. We have changed volt regultor, the ignition switch, and we can't figure out what is going on. Now, we are getting no power. Can anyone please help me?

 

check the basics first, are the battery connections tight and clean, is the battery at or above 12 volts.
What fuse was blown?
What happens when you try and start it, no crank, clicks, lights dim. A little more info may help.
a common thing to go bad is the starter relay.

 

The battery is good. The connections are tight. There is no power, no clicks, no lights. There is nothing now. The battery is 12 volts. The fuses are fixed.

 

If you have no power to anything then check the fusible links and the connection on the starter relay. check the main battery cable between the battery and relay. if you have a multi meter check the voltage drop across the cables.

 

we've changed the starter selonoid,ignition switch,all but 3 fusable links,new ground cable on battery. 5 months ago we changed altenator,starter and the fusable links to altenator along with new plug. Now no power to anything electrical. No cab lights no radio no headlights no nothing.The battery was load tested and was found to be good.

 

start at the battery and check for voltage. move along from one thing to the next. the first thing after the battery is the starter relay then from there the wires branch out to things like the relays, fuse panel, ignition switch and distributor.
I would suspect the problem is between starter relay and the battery or the grounds. Maybe the harness is damaged somewhere between the starter relay and the cab.

 

had similar problem power to everything except starter,no clivking or anything. Check the cheap *** connector at starter motor,my 97 4.6 had this problem.I toook off plastic enclosure to access the female connector,used contact cleaner and a wire brush to clean then tightend crimp on female end from harness. Put it back on male blade and it works good for another 6-9 months then it starts again.Lousy design,catches all the road splash, and connector relys on good press fit

 

I wonder if your fuel pump has bit the biscuit.

You mentioned you had radio etc. Was it cranking at all?

 

Did the "no power anywhere" start after you changed some parts? Double check to make sure you have the wiring at the starter relay wired correctly.

Had a buddy that installed a new relay, and mistakenly installed all the wires that go on the battery side of the relay, on the starter side of the relay, and wanted to know why nothing worked anymore. As soon as I saw it, it was fixed.