Truck I'm restoring myself for my dad. 2001 f150 scab 4x4 5.4l. It's been sitting for about a year while I've had the interior out. About 4 months ago I started the truck, it did require a boost but ran fine after removing cables. Today I finish up the dash panels and go to start truck, battery dead. Pull my 250 over and hook cables up and after a few minutes truck starts right up. I let it run with cables for about 30 minutes and removed cables. Truck instantly died. It starts back with cables but dies as soon as taken off. After it dies if you go to start truck it won't turn over or anything as the battery is gone. I realize I may need a new battery but is there a chance my alt is bad also because it won't stay running?

Thanks in advance

 

I say replace the alt.

 

Check all of the wiring going to the alternator, starter, and battery. Make sure all of the connections are clean and put some dielectric grease to keep the moisture away. I would agree that you probably need a new alternator. Remove it and take it to get tested. If the alternator isn't charging and the battery is bad, it won't stay running. Not sure where you live, but out here in the country we have field rats/mice that will chew all of the wiring up in the engine bay if left for a while.

 

Yea, they won't stay running that long with a bad battery, - sounds like your is beyond shot lol. Manuellabour247 and pc03fx4 are correct. You need to confirm the alt, - you can do that right after you jump it with a muti-meter.

Red to positive/black to alt case. What's the meter say?

Then check just the battery w/meter, - what's that reading?

That will give you direction needed at first. Alternators were never designed to charge a battery. They're meant to maintain battery charge. If you've never re-charged the battery with a charger, you may want to start there.

But yea, confirm the alt first, - that's easy to do yourself.

 

Sounds like your alternator lost a negative diode inside (possible arc of cables?) which will cause a draw down of a weak battery. I'd say replace the battery then have the alternator checked, or do it yourself with a good digital meter. Good luck.

 

Thanks guys, I have a small meter that I use for small electronics. Can I use this on the battery and alt? I'm going to take the alt and have it tested tomorrow and hopefully grab a new battery

 

And Manuelle I live in South Carolina in the middle of about 50 acres of farmland. Field mice are always a concern here and I will lose my mind if this is the case. Tracing all the wiring in the engine bay doesn't sound in the least bit fun.

 

Yea, you don't need to take the Alt off unless it's not working. Like I said, you have to check it while it's the trucks running to see if it's putting out..anything. The alt will read different than the battery.

Yea, any multi meter will work.

Here's how. With the truck off, no jumpers connected, -check the battery voltage. Record it, write it down.

Now jump the truck, get it started. You posted that it will run for a bit before stalling correct ? So pull the jumpers while it 's running, -right away, check the alt like I described earlier.

What did you get?

 

And Manuelle I live in South Carolina in the middle of about 50 acres of farmland. Field mice are always a concern here and I will lose my mind if this is the case. Tracing all the wiring in the engine bay doesn't sound in the least bit fun.

 

Honestly, depending on if that's the case, there are a lot of junkyards around the country with these trucks. I'd get a whole new harness. Lol. I hope it's just a dead cell in the battery or the alternator. I hate wiring, and I wouldn't wish tracing all of those wires on anybody.