Make: Maruti Suzuki
Model: 800 hatchback
Engine: F8B MPFI
Battery: Exide 35AH 2.5 year old Rated OCV 12.92
Location: Nagpur, India. Daytime Temp about 44C
Background: Around November/December 2017 minutes after after encountering a sudden level change at speed the engine cut out. This was diagnosed to be a stripped timing belt; the original having lasted close to 70000Km.The clutch has also been replaced as per inspection and replacement schedule. Occasionally upon starting, the engine would suddenly race, and shudder violently at random but never reproducible at the workshop. Similarly there was an occasional instance of what felt like a misfiring plug in both cold and hot start; also not reproducible.
The problem: The evening before last the vehicle served a short run; a few Km. Yesterday morning on a cold start the starter turned but the engine cranked very slowly thud thud and died. Subsequently the starter whined but the crank did not turn. It sounded like ... https://vocaroo.com/i/s1SiqOpBShQ5#
With the battery showing 12.86V I put it to charge around 8H by which time it had come up to 12.9. Upon the third attempt the engine fired. Putting the multimeter against the battery with the engine running showed the voltage at 13.62V. However occasionally this would fall all the way to 3V, and then recover.
Driving the car to the workshop where the Bosch starting system tester was applied showed all good. In one instance when the alternator was tagged bad, racing the engine had the alternator reported good on all subsequent tests. The master mechanic even pulled the battery ground without killing the engine albeit the engine did balk a little when the terminal was reconnected.
The master mechanic recommended a wait-and-watch policy; which I am not comfortable with. His take on the recording was that it sounded like a timing issue.
My questions: What can I do to reproduce this problem? The occasional drop in the voltage has me leaning in favour of a faulty regulator, or alternator assembly being the cause; how can I confirm this with only a basic digital multimeter at hand?