Is there any other reason why a diesel mk1 would crank slow on start up other than a bad battery? My battery shows 12 volts when nothing is on. When I turn the key on to check volts at the starter and stop solenoid it's at 10v. I'm pretty sure it's a bad battery but I won't be home for a couple days to switch 1 out. Anything else that might cause it to crank slow?