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I have a 2002 7.3 that is turning over slow. Both batterys are reading 13.6 while engine is running. I do show a positive voltage drop of .30 on the alternator under load. Any suggestions greatly needed.
What are the batteries reading when the engine isn't running?
Just a side note, my truck was turning over slow a few years back, bearings in the starter were almost frozen up. Replaced them and the starter is still going strong today.
Driver side battery is 12.40 and the passenger side is 12.42. I have a rebuilt starter sitting on bench, I just want to be sure it is the problem.
Batteries seem to be okay, you can load test them and that would give you a better indication of there state. I would change out the starter cause you already have it. Then, I would try this test I found on the net if you don't have a load tester to check them.
There’s more to checking a battery than testing the voltage and looking inside for low water. For one thing, you need to check the voltage when the engine is off, not when the alternator is raising system voltage to its normal level. You can test for proper cranking voltage with a voltmeter while—you guessed it—cranking the engine. The several hundred amperes of current the starter motor draws should pull the battery voltage down to a normal 9 to 10 volts. Do this test: Disable the ignition or injection to prevent the engine from starting. Then put a voltmeter across the battery posts while cranking it with the key or an external remote starter button. Crank for 15 seconds (no longer); the battery voltage should remain 9.6 volts or above.
Need to check the voltage while cranking. Should stay around 11 volts or better. Any less and you're going to be slow. You can always go by AutoZone and have them load test them for you.
Had the same thing and checked everything like suggested here and turned out to be the starter after everything. It is so easy to change and you already have one so
The batteries are around 20 months old. The starter was showing signs of fatigue at the close of a very cold winter so that is why I have a rebuilt one in garage. I am going to change it out and clean all connections then hope it works fine. Thanks for all the advice.