Gehl Telehandler Kept Dying, but It Wasn't a Fuel Problem
When a diesel telehandler repeatedly shuts down, the fuel system is an obvious suspect. Restricted filters, fuel delivery problems and air entering the system can all cause similar symptoms. On this Gehl RS8-42, however, the actual problem was electrical.
The telehandler would run and then unexpectedly die. Our technician connected a scan tool and reviewed the engine data. No active fault codes were present, but the ECM supply voltage displayed only approximately 11 to 12 volts.
The most important clue appeared when the engine shut down: the engine data changed to “not available.” That indicated the diagnostic tool was losing communication with the ECM as the failure occurred.
Voltage measured at the alternator and starter terminal was approximately 13.5 volts, showing that the charging system was producing voltage. However, voltage at the charging source does not prove that the same voltage is reaching the ECM under load.
The technician accessed the ECM wiring and backprobed its power circuits. The ECM battery supply dropped to approximately 9 volts under load, while the ground and key-switch voltage tested correctly.
Following the ECM power circuit back to its source led to the positive battery connection. A previously replaced battery lug was severely corroded and creating excessive resistance. It could pass enough voltage to appear acceptable during a basic check, but it could not maintain ECM voltage while the machine was operating.
The damaged connection was removed, the cable and connections were cleaned, and a new lug was properly crimped onto the cable. A stud-to-post battery terminal was then installed. After the repair, the circuit was retested and no further voltage drop was found. The telehandler remained running and was returned to service.
This repair is a good example of why intermittent equipment problems require testing the complete system. Replacing fuel components, or even the ECM, would not have corrected the underlying problem.
Mondak Equipment & Hose provides equipment-level electrical, electronic, hydraulic and mechanical diagnostics. When a telehandler, forklift, aerial lift or construction machine has an intermittent or difficult-to-find problem, contact our team.