Hello, We have a JLG 400s s/n- 0300101674 / DEUTZ diesel powered that came back from a job with the following problem. When you go to start the machine, sometimes it will crank but not turn on over then sometimes it does turn on but the engine revs EXTREMELY HIGH that we have to shut it off right away. We replaced the throttle actuator thinking it was that but it remains the same. Any suggestions on what it could be?
check the harness where it goes down underneath the engine. it rubs near the oil pan. Also check your target/actual speeds on the analyzer
If it is truly over speeding to more than max governed RPM it's not an electrical issue. If you remove the actuator the engine should run at max governed RPM. The springs on the actuator push the rack back toward less fuel delivery. The rack moves according to the governor arm position and flyweight push. With the actuator removed reach in the hole and check that the rack moves freely.