Rob,

U should do the voltage test at the GP terminal when the current is going thru the GP. Open circuit voltage tests don't always mean much.

I have a W116 with a 617 engine and the GP light is very intermittent. Some times it lights, sometimes it doesn't. But that doesn't have any effect on the GP and the engine starts easily as long as I wait long enough for the GP to get hot. I didn't think this problem was worth spending the time to fix it.

Try waiting longer before turning the key to the start position and see if this makes any difference in how the engine starts.

P E H