The contactor solved my 8kw RPM sense error code. The contactor problem was intermittent. After several times starting it in manual I heard a heavy "click" but the starter didn't power up.
I did the same as you and replaced both the contactor and the coil. I gapped the coil about .010 inches from the magnet.
Everything working good now.
Just got my parents 7KW generator back up and running properly after an RPM sense error code and difficulty starting. Replaced the battery, unknown age but at least 5 years old. Ordered the two parts MEC linked to from Ziller. Only installed the contactor and properly adjusted the valve lash to .003. They were tight! Generator started right up!
Thanks to all for posting questions and to the technicians for providing guidance.
BTW, I didn't have a 10mm allen wrench so I used a T-55 internal torx socket. Worked fine as an allen wrench replacement.