JD 5105 wont start

Greg in MS · Dec 31, 2021

I have a 5105 that I cant get to start. I believe I have a bad safety sensor, but dont know how to check. Plenty of battery, all fuses good. Tractor wont turn over from key. When I jump at the starter it turns over plenty fast but wont start, a little ether gets it to hit a few times. It acts like the neutral sensor is not working, I have unplugged that and it still wont turn over.

Any ideas?

Jim.ME · Dec 31, 2021

Unplugging the connector from the safety sensor would be step one. Step two would be to use a wire and jump the two terminals in the connector you unplugged from the sensor together to complete the circuit.

You didn't say, but did you have the key turned to the run position when you jumped it at the starter? And please be sure the transmission is in park or neutral when jumping it at the starter.

Timmycornpicker · Dec 31, 2021

If I recall, those tractors have an electric relay circuit for fuel shutoff, which must be energized in order for the tractor to run. I'd confirm if there is
power coming off the key switch.

Greg in MS · Dec 31, 2021

I didnt try jumping the connectors (I did unplug and
try) in the neutral start safety switch. I did have the
key in the run position when I jumped the starter. Ill
give that a shot.

Thanks.

Greg in MS · Dec 31, 2021

I believe that is correct, so just jumping the starter doesnt seem to work. I cant tell from the shop manual if a bad neutral start switch would keep the fuel shut off if I just jump it at the starter.

Jim.ME · Dec 31, 2021

Usually, the neutral start switch only disables the start circuit. Turn the key on and use a test light to see if there is power to the terminal on the injection pump for the fuel shutoff. If that is dead as well as the start circuit, you may have a bad wire or connector behind the dash or through the cowl panel.

Mike M · Dec 31, 2021

Plenty of relays on those.clear down at the bottom left below the dash.I had the one for the injection pump shut off loose power when cranking but had power with key on and checking with test light.

Jim.ME · Dec 31, 2021

Is your range shift lever in neutral (Neutral start safety switch would be affected by this)? Check to see that your PTO is disengaged. There is apparently a safety switch on that as well.

MSM · Jan 1, 2022

neutral safety switch only affects cranking, not the fuel solenoid.

tim s · Jan 1, 2022

Some have a thermal switch up near the temp sender, it is to aid in cold weather starts,, they go bad and take out the fuse or relay,,unplug it and see if that makes a difference,, my bet is it will,,if your not sure which one,, unplug both of them,,the one in question will have a lead that goes in with the pump harness,,if this is the issue just leave it unplugged, you will not know any difference,,it is just another electronic gizmo that the design team threw in to make them more undependable...

JD 5105 wont start

Greg in MS

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Jim.ME

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Timmycornpicker

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Greg in MS

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Greg in MS

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Jim.ME

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Mike M

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Jim.ME

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MSM

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tim s

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