Loud Knock at Crank

[jconner00]

Friends,

Just about every 10th-20th start of my truck I’ll hear a loud knock just after the initial turnover. Today I happened to finally capture a video of the moment it happened. Tomorrow she goes in for an oil change and I’m going to show them this but would like to have an idea of what it could be. TIA

In the attached video you can hear it at about the 1 second mark.

 

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[gemarsh]

Friends,

Just about every 10th-20th start of my truck I’ll hear a loud knock just after the initial turnover. Today I happened to finally capture a video of the moment it happened. Tomorrow she goes in for an oil change and I’m going to show them this but would like to have an idea of what it could be. TIA

In the attached video you can hear it at about the 1 second mark.

As fast as it's firing up, I'm going to spitball and say it sounds like the flywheel is spinning up faster than the bendix can kick out. The flywheel teeth are hitting the backside of the bendix teeth.