606 Starting Issue

[aklim]

99 E300 with 300K on the clock that we are working on here.

Starts good when cold. When you drive it for a bit and shut down, the engine seems to crank slowly like a dead battery. Jumped it, charged it but still the same. Good cold start but when warm it turns like the battery is dead. Battery is at 12.7 volts and the charging system when running brings it to a little over 13V.

I am suspecting heat soak on an older starter. Original to the best of my knowledge.

I am tempted to say it is the starter but any other clues as to what it could be besides heat soak on an old starter that is going out the door?

TIA