07 GMC Sierra 5.3 l. Start issues

Old 10-02-21, 02:40 AM
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07 GMC Sierra 5.3 l. Start issues

My 07 GMC Sierra Classic Z71 with the 5.3 literis needing to be jumped almost every time I try to start it. It will crank for second and then it acts like the battery is dead. The starter bogs down and stops, the lights dim, etc. Which we oils indicate improperly charged or bad battery, normally. But I can try to jump it off of the 3 house batteries from our Motorhome that are new and fully charged and it will do the se thing. But if I put a NOCO jump-started on it it doesn't hesitate. Fires right up like it should? I've also tried a marine/RV battery that has even more CCAthan the truck calls for and it again does the same thing. I'm going to try swapping out the battery to see if that fixes it. Any input/ advice would be greatly appreciated! Thanks to all.
Old 10-02-21, 03:08 AM
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Go through all your "large cable" connections. Thoroughly clean and tighten all cable connections between the battery and starter and see if that helps.
Old 10-02-21, 06:57 AM
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Checking your cables and grounds is a great idea.
House batteries are deep cycle, starting batteries are shallow cycle. I recommend using only shallow cycle (starting) batteries to avoid confusion.
I'd start by testing the voltage on the truck battery. It should be at least 12.5v static. Also check how well it is grounded by seeing if voltage reading is same when measuring ground on the engine. I know this is not under load, but could help identify a basic connection problem.
Measure the battery voltage during a start. The voltage should drop no lower than 9.6V or so. If it goes lower than that then either the battery is not strong enough to turn the starter, or, the starter is faulty and asking for too much power. If you don't get much of a drop during the start, then either starter is bad or grounds need cleaning.
Old 10-02-21, 07:42 AM
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Its hard for me to say at this point if its a bad battery or not. I'd certainly start with cleaning the cable ends to make sure they are clean & get a good connection. That seems like the best place to begin with based on your post info. If you can, inspect the cables for corrosion under the plastic cover. Corrosion will sometimes travel from the clamp down the wire under the plastic covering & you may not know that the cable itself is bad. Just give those cables a good look.
If it doesn't start good after cleaning the cables, jump start the truck & take it to Auto Zone, NAPA or O'Reily's etc & they will do a battery load test on it & see if its a bad battery. If the battery is good, I'd change both cables and go from there.

Good luck.

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