A lumber yard reported that a Hyster S80FT LPG forklift would not start. When the key was turned, the starter solenoid just clicked rapidly (chatter), but the engine did not turn over. The battery was tested and found to be fully charged (12.8V).
The technician measured the voltage at the starter motor terminal while the key was turned to "Start." The voltage dropped to 9V, indicating high resistance in the circuit. He checked the ground strap from the battery to the chassis. It was tight. He then inspected the main power cable from the battery to the starter. It looked fine externally.
He then focused on the "Bulkhead Connector" (the firewall plug where the main wiring harness passes through). Upon unplugging the connector, he found that the pin for the "Starter Solenoid" wire was severely corroded (green oxidation). The pin was almost dissolved. This corrosion created high resistance, limiting the current flow to the solenoid. The solenoid would pull in, but the voltage dropped too low to hold it, causing the "chatter."
However, after cleaning the connector, the engine still struggled to turn. The technician suspected the starter motor itself. He removed the starter and disassembled it. The brushes were worn down to 20% of their length, and the commutator was blackened. The starter was drawing excessive current due to internal friction.
The repair involved soldering a new wire and pin into the bulkhead connector harness (using a waterproof Deutsch connector) and installing a re-manufactured starter motor. He also cleaned the battery terminals. The engine cranked strongly and fired up immediately. This case highlights how electrical faults often mimic mechanical failures, and a systematic voltage drop test is the only way to isolate the root cause.
