tractortrash
New member
I am helping a friend whose JD5103 will fire with the key in the start position then dies when the key is released to the ignition/run position. This is an intermittent problem, more often occurring in cold weather. I determined that bypass start relay #2 is energized inappropriately after the starter is cranked, based on the following tests. #1 the fuel shutoff solenoid is powered on initially then loses power when the key is released from the start position. #2 replacing bypass start relay 2 with a jumper wire between terminals 30 and 87A eliminates the no start condition. #3 the engine can be started by cranking the starter then quickly switching the key off then back to run while the engine is still turning over (this resets bypass start relay 2 and re-energizes the fuel shut-off solenoid).
My JD5105 service manual describes this no-start condition (engine dies when key is released from start to run position) and describes a 3 ohm, grounded resistor on circuit 313 that is designed to draw off a small amount of current generated by the freewheeling starter motor, in order to prevent activation of bypass start relay 2. I tested the resistor and wiring on the JD5103 and it has 3.1 ohm resistance. We cleaned the terminals and reattached the resistor, reseated the 2 diode packs, and the bypass start relays 1 and 2. The no-start condition is unchanged.
I am thinking about throwing new parts at this intermittent problem (resistor, diode packs, bypass start relays), but thought I'd first ask for advice. Could a sticky pinion gear on the starter cause this problem, by keeping the starter engaged on the rotating flywheel a bit longer, even with a functional resistor in the circuit? The tractor is ~10 years old. Does anyone have experience fixing this problem?
My JD5105 service manual describes this no-start condition (engine dies when key is released from start to run position) and describes a 3 ohm, grounded resistor on circuit 313 that is designed to draw off a small amount of current generated by the freewheeling starter motor, in order to prevent activation of bypass start relay 2. I tested the resistor and wiring on the JD5103 and it has 3.1 ohm resistance. We cleaned the terminals and reattached the resistor, reseated the 2 diode packs, and the bypass start relays 1 and 2. The no-start condition is unchanged.
I am thinking about throwing new parts at this intermittent problem (resistor, diode packs, bypass start relays), but thought I'd first ask for advice. Could a sticky pinion gear on the starter cause this problem, by keeping the starter engaged on the rotating flywheel a bit longer, even with a functional resistor in the circuit? The tractor is ~10 years old. Does anyone have experience fixing this problem?