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Clayso, Master Automobile Technician
Category: Australia Car
Satisfied Customers: 880
Experience:  ASE Master Certified Automobile Technician. 30 Years Experience.
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Holden Commodore VX 6cyl: RichI am trying to diagnose

Customer Question

Hi Rich
I am trying to diagnose a slow cranking engine. it happens more often than not but is an intermittent problem. Battery voltage OK, connections all clean and tight. voltage at solenoid starter motor terminal is a fraction under 9 volts when starting (but is not turning slowly at the moment). I have a workshop manual that says a slow cranking speed with voltage over 9 indicates a faulty starter motor, slow cranking speed with voltage under 9 indicates burned solenoid contacts. Normal cranking speed with voltage over 9 is all OK, but there is no mention of a normal cranking speed with voltage under 9. Any idea if there may be a problem with the starter/solenoid or might I be going down the wrong path.
Submitted: 2 years ago.
Category: Australia Car
Expert:  Clayso replied 2 years ago.
Hi There, I'm Clayso a certified master automobile technician with 30 years of automotive repair and diagnostic experience and I'm here to help with this problem. Additional services may be offered for detailed information.
From your description it sounds like the battery is low on charge or failing. Computer controlled powertrain management systems require adequate battery voltage to operate properly. Batteries should have a minimum of 12.6 volts and should maintain above 9.5 volts under a full load. Load testing removes amps from a battery much like starting the engine. Most all batteries are labeled with the amp load for testing. This number is ***** 1/2 of the CCA rating. For instance, a 500CCA battery would load test at 250 amps for 15 seconds. ACDelco lists P/N: 22F530SMF for this vehicle at 530 CCA. A load test can only be performed if the battery is near or at full charge. Starting and charging systems should only be tested with a fully charged battery.
Minimum battery state of charge 12.6v (no load)
Minimum battery state of charge 9.6v (with load/starting)
Proper battery charge rate 2 amp or trickle charge for 8 hours
The life-span of all batteries is linked to the capacity of the battery (e.g. in Ampere hours) and the amount of current (Amperes) drawn from the battery by the device which it powers. Temperature, humidity and other environmental factors also have an impact on battery life-span. The expected automotive battery life is about 60 months under normal conditions. Most all automotive parts stores can properly load test your vehicles battery.
I hope this information is helpful to you.
Should you have any questions please let me know.
Thanks so much.
Customer: replied 2 years ago.
I know the battery is good as it is brand new. The battery also works fine in my other car of identical model. The problem is related to something other than the battery. Can you please address the question, assuming the battery is good.
Expert:  Clayso replied 2 years ago.
Sounded like a battery problem to me. I have to opted out and return your question to the forum. I'm limited on technical information for this vehicle.
No reply to this post is necessary.
Customer: replied 2 years ago.
Just refund my money please, I am not confident you will be able to answer to my satisfaction

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