Troubleshooting the starting circuits when the engine was unable to 'turn over' successfully with the plugs installed. Without the plugs (no compression possible) the starter easily turned the prop at acceptible rotation speed. With compression it was not able to turn 1/2 revolution. In addition, the 'ground lead' on the ignition switch was excessively hot within 5 secs of applying power to the starter.
Reviewed the circuits and ascertained that the engine flexible ground strap was never attached to the FW common ground, causing the ignition ground lead to carryt too much current.
Temporarily connected the new flexible ground strap to the FW ground point and successfuly rotated the prop at very acceptable rotation speeds and no wire heating problems on the ignition ground lead. Cause - insufficient grounding of the engine (i.e., strater to the FW) to carry the current load needed to operatie starter. Solution - good ground strap.
Needs permantent configuration of the new ground strap.
