I just bought a 2009 5.4l from a dealer 30 days ago. They are 3 hours from me, so it makes it hard to take it to them. I was not able to start the truck for the past two mornings. After I jumped it, it ran all day. Then the next morning it was dead again. Can you test the alt by pulling a batt cable while it is running to see if it still runs?


Thanks
pt

 

I haven't tried that old school method on our trucks, but it might work. A more reliable method would be a multimeter on the battery post. Anywhere between 13.5-14.5 volts while running(depending on what is all on, radio etc). If you don't get that move to the battery connections to rule out dirty post, but my money is on a dead battery from your symptoms.

 

I have cleaned the cables and terminals. I was hoping the old method would work... The battery is charging now, so I'll have to wait for a while to check with meter.

 

Check alternator output at the alternator with a multimeter whith engine running to rule out the alternator. If you check it at the battery, it won't be as accurate as cables could be corroded giving false readings. As stated, it should be above 13.5 volts. It does sound like the battery is the culprit though.

 

Yes, although the engine may rev a little intermittantly. My wife's '99 Sable would rev up and down between 500-800RPM when I disconnected the battery with the engine running.

Remember to pull the positive cable from the battery, not the ground.

 

So the battery charged enough to test the old school way. It runs with the positive cable discounted. To add to me bad day, my volt meter stopped working. So not able to test the voltage yet. Does that mean the alt is good? The battery seems to take enough charge to start it but dead past two mornings...

 

The battery is not holding the charge though. Load testing the battery can confirm, but not everyone has access to one. Pretty sure the battery is toast.

 

Sounds like the Alt is good to me.

 

Parasitic system draw could also be an issue, disconnect the battery cable and lightly brush it against the battery post and see if you get a noticeable spark. Make sure all doors are closed, lights are off and any device you may have plugged in disconnected, cell phone charger etc... first.
.

 

I managed to get the truck into the local Autozone. They "Tested" the battery and said it show 100% charge, but the battery was bad. So I bought a new one. What goes bad in battery to show charged but bad??? So we'll see how it goes the next few days. I'll also be checking for any electrical draining...