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99 F350 7.3 Electrial Problem

 
  #1  
Old 03-15-2019, 03:57 PM
JoeLawrence73
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99 F350 7.3 Electrial Problem

My F350 will not start without being jumped. When the truck is off both batteries read at or slightly above 12.5 volts. When it is running after I jump it, they read 14 volts.
Any ideas as to why this may happen? Could it just be the starter going bad? It is original.
 
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Old 03-15-2019, 09:06 PM
oharal
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What's the date code of manufacture on the batteries? No load voltage doesn't tell you anything about the health of the battery, only that it is charged. They could be worn out and have high internal resistance. You can check with your multimeter. What does the voltage drop to when cranking? Additionally, be sure to check ALL of the connections from the B+ on both batteries all the way to the starter post, and B- on both batteries all the way to the engine block.
 
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Old 03-15-2019, 10:43 PM
99f350sd
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Sounds like the batteries are toast. Voltages are good. More than 4 or 5 years old?
 
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Old 03-16-2019, 10:22 AM
alloro
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Originally Posted by JoeLawrence73 View Post
My F350 will not start without being jumped.
It needs to be jump only when sitting a long time like overnight, or even when you run into a store for 10-minutes and come back out?
 
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Old 03-16-2019, 11:33 AM
Fefanatic
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Overnight is not considered a long time by any means. The battery can have good voltage but not have any cranking amps. If you are reading 14 volts while running the alternator is good. Time for new batteries.
 
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Old 03-16-2019, 05:17 PM
TrucksNCoffee
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Used to be that auto parts stores would test your battery with a load tester they kept on hand, free of charge. Smart move, this, 'cause if the battery needs to be replaced, you're already there and they'll sell you one, on the spot.) I think they still do this, no?
 
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Old 03-16-2019, 11:36 PM
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7.3 needs a minimum of 10.8 volts while cranking to start, resting voltage doesn't mean much at all. I'd say your batteries are obviously toast. Yes, most stores will load test them for free. If only one tests bad, still replace both.
 
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Old 03-17-2019, 12:17 PM
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Originally Posted by Fefanatic View Post
Overnight is not considered a long time by any means.
It's enough to determine if there's a different result versus sitting 10-minutes. Which in turn could change the focus from batteries to the starter or not.
 
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Old 03-17-2019, 05:18 PM
1Truck
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Your batteries read 14v while running because you are reading the voltage being produced by the alternator. You can have a dead cell which eventually could prevent the truck from being jump started. This would also cause the charge to rapidly deplete.
you could also have a bad alternator which is draining the battery. Replace batteries, if problem persists, replace alternator.
 
 


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