engine starter troubles

[conndor1]

Howdy yall,
first time poster here
I recently did a bunch of work to the engine, perkins 4.108, and when i went to start nothing. so i replaced the solenoid that is seperate from the starter and then i heard the starter trying to engage but not turn over. so i thought the starter and then changed that and still same problem. so i measured the voltage at each side of the solenoid and it goes from 12-13v to around 8v on the other side. so then i think bad solenoid from the store. well two more solenoids later and still same thing. there are three power wires going to the in side of the solenoid. one comes from the battery, one to the alternator voltage regulator, and the third i dont know where.
any help in getting this engine started would be greatly appreciated.

[kmacdonald]

The battery would be a good starting point. What size cable runs from the battery to the starter? Check connectors. Can you turn the engine over by hand even a little?

[Lepke]

As kmacdonald said, make sure the engine can be turned by hand. It's not likely you got 3 bad solenoids. Either a bad connection (positive or ground), bad battery, bad starter, shorted start wire from the key.
Touch a screw driver, or other solid metal between the two heavy posts on the solenoid. Sparks will happen, but the starter should turn over the motor. To test the wire from the key, touch a short piece of wire between the heavy post (from the battery) to the terminal (usually marked with an "S") that the wire from the key attaches. That bypasses the whole key wiring.
If the engine turns by hand and the touching across the two heavy posts doesn't get the starter to turn, you probably have a bad starter. Before buying a new one, make sure your starting battery, cables, and any connections are good. New starter and solenoid on ebay about $100.