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Batteries load tested ok but voltage dropping

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Cubey, Oct 21, 2018.

  1. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    They are toast. At least one is(electrically one drags down the other battery), and they need to be replaced in pairs.
    12.8v is standing voltage and to be at 12.4 so quick after driving 30 mins is a bad deal. I just went through something similar.
     
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  2. Oledirtypearl86

    Oledirtypearl86 Full Access Member

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    Did you try ether after stall If so kinda sounds like a fuel issue for how's your fuel pressure
     
  3. Macrobb

    Macrobb Full Access Member

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    So, two things:
    After cranking for a bit and then checking, I could totally see 12.4V on the batteries.

    Our starters(all types) have 4 brushes contacting the armature. If one of these four wears out to the point of a bad connection, the starter will run at about half-speed. Sounds like a dead battery, even with full voltage.
     
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  4. Cubey

    Cubey Full Access Member

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    Edit: oops, replied to a post directed to someone else.
     
  5. ABNORDY

    ABNORDY Registered User

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    Fuel pressure running between 6 and 7lb a few week prior, cannot check now as there is not enough juice to get the truck to start, I di replace the mechanical fuel pump a few months back.
     
    Last edited: Jan 23, 2019
  6. ABNORDY

    ABNORDY Registered User

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    I agree, borrowed 2 Yellow top Optima Batts from work. Gave a bit more umf, but but not enough to start. Lifetime warranty Starter, just a friggin pain in the A$$
     
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  7. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    If those batteries were charged then you have a bad connection at the starter, the wire/terminals, or inside the starter itself. There's only so much that can be going on here.

    A voltage drop test would help pinpoint the issue, lots of good videos on YouTube about that.
     
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  8. DrCharles

    DrCharles Full Access Member

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    Yep... I would start by just measuring the voltage directly at the starter while cranking. From the stud itself to the body of the starter. If it's good, the problem is the starter. Otherwise start chasing bad connections.
     
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  9. ABNORDY

    ABNORDY Registered User

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    Well, I attempted to start with the Optima Batteries. Very sluggish at first 13 VDC, crank for longer than usual maybe 30 seconds, after about 10 seconds the starter sped up but nowhere near "normal" speed, still no start. Began to smell that unique electrical burn. Turned key to off position and starter stay engaged, disconnected batteries, felt batts for heat, definitely cool to touch, battery cable a little warm, went down to starter, very hot and untouchable! Batteries ended up at 12.7 VDC. I am now convinced the starter is AFU! Checked at O Reilly's and had to order the warranty starter, will be in on Friday. Going to build all new cables at work tomorrow.

    Sent from my SM-N950U using Tapatalk
     
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  10. ABNORDY

    ABNORDY Registered User

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    Did that tonight 13 VDC to 12.8 in a 25 or 30 second time span!

    Sent from my SM-N950U using Tapatalk
     
  11. 79jasper

    79jasper Chickenhawk

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    They seem to always do that before releasing the shmoo.

    Sent from my SM-N960U using Tapatalk
     
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  12. ABNORDY

    ABNORDY Registered User

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    Well, I had been on the road for a few weeks, finally got home yesterday and replaced the starter. Yes, the starter was to whole problem!
     
  13. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    Glad you got it working again!
     
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