A recycling facility reported that a Hyster H2.50D (Isuzu engine) forklift would struggle to lift heavy bales of cardboard. When the lift lever was pulled, the dashboard lights dimmed, the engine RPM dropped drastically, and the hydraulics groaned. If the operator held the lever, the engine would eventually die.
The technician initially suspected a hydraulic relief valve or a clogged hydraulic filter. He checked the main relief pressure, which reached 180 bar, but the engine nearly stalled when it hit relief. The flickering dashboard lights were the critical clue pointing to an electrical issue. He connected a "Digital Multimeter" across the battery terminals. With the engine off, the voltage was 12.6V. With the engine idling, it was 13.8V. When the lift lever was engaged, the voltage plummeted to 9.2V.
A voltage drop of this magnitude under load indicates a massive resistance in the charging or grounding circuit. He traced the "Chassis-to-Engine Ground Strap" (a braided copper cable connecting the engine block to the forklift frame). The strap was heavily corroded at the chassis bolt eyelet, and the braided copper had turned green.
The forklift's hydraulic pump is driven directly by the engine. When the operator pulled the lift lever, the hydraulic pump loaded the engine. The "Fuel Solenoid" (which holds the fuel rack open) and the "Engine ECU" require stable voltage to function. The corroded ground strap created such high resistance that the electrical circuit sought a ground path through the throttle linkage and dashboard wiring. The voltage drop to 9.2V was so low that the fuel solenoid couldn't hold the rack open, cutting fuel delivery, which caused the engine to lug and die. The hydraulic groaning was a symptom of the engine losing RPM, not a hydraulic failure.
The repair involved cutting off the corroded ground strap eyelet and crimping a heavy-duty tinned copper lug. The chassis mounting point was sanded to bare metal, and the new strap was bolted down with dielectric grease. A second redundant ground strap was added for safety. The forklift then lifted full loads with the engine maintaining 1500 RPM and the dashboard lights staying bright.
