AoA Guys!
Recently i was facing the problem of weak cranking when starting the warm engine. At first i thought the battery is dead but things went differently. I checked starter motor but there was no fault in it. Battery was fine(mechanic insisted that battery is bad but load test results were good). I Also checked terminals for corrosion but no sign, cleaned them still. Still nothing changed. All i achieved was a Poker Face.
After reading and searching on internet i found that cables become weak and resistance develops and this is what happened. I measured the voltage drop from -ve battery post and engine block when engine was cranked and the drop was 0.374V the wires were fully tightened on both sides and there was no corrosion. According to articles on internet the drop should be below 0.25 volt for -ve side. I measure the drop on positive side and it was 0.12 v( acceptable range < 0.7).
So i made another ground cable using 4 heat and gasoline proof 10AWG copper wire and after connecting the voltage was just 0.068 V during cranking rather than 0.374V. And the problem on hot start has been solved now.
Conclusion : Don't believe like blindfold on mechanics. Always conduct a voltage drop test
Pics Attached for reference.