John Deere 5105 wiring diagram

glockky

Member
Well I just bought the 5105 and it worked great till this morning. The tractor will sporadically not want to start. Funny thing is if you keep the key switch over in the start position the tractor stays running but as soon as you let the key drop back to the run position the tractor dies.

It will do this a few times them start no problem at all. I traced the problem to the wire going to the injection pump. When the tractor starts and dies the voltage stops going to the injection pump. When the tractor starts and runs correctly it keeps 12 volts to the injection pump.

The problem is I can’t figure out what is causing the power to go in and out to the injection pump. I haven’t been able to locate a wiring diagram anywhere. I assume there is a some type of relay going in and out or the key switch is going bad.
 
I also want to add that I think the wire that going to the injection pump is actually powering the fuel shutoff solenoid but I’m not positive.
 
Shoot me your email, I have a PDF of the tech manual you're welcome to, has the wiring in it

Joe
 
Mine drove me nuts after I changed the fuel filters and tried restarting it. One of the first things I checked was for power at the inj. pump when I turned the key on. What I did not do was keep checking for power as I cranked it ! Mine the power was dropping out when I cranked it. your sounds like it is doing the opposite ?
I ended up removing all the relays.Cleaning them up and sticking them back in different locations. There is a panel full of them at the lower left side of the dash. I don't know why it has so many ? and I don't think many are even used on this model ? Owners manual is useless on this. I do have it marked in my manual which one is for the fuel shutoff now , but it is at home. I can check tonight if I remember.
 

After looking at the wiring diagram it looks like the only thing between getting fire from the battery to the fuel shutoff solenoid on the injection pump is the ignition switch, a fuse, and the starter relay.

I have tried to test mine but it’s so sporadic it’s hard to tell what’s failing. I’m going to start with the ignition switch. My switch feels loose and sometimes wiggling the key around gets it to start up. Although that may just be a coincidence.

If the ignition switch fails to fix it I’m going to replace the starter relay.

I may also get a good contact cleaner and clean all the diodes and relays while I’m changing the ignition switch since it all right there in the same area.
 
The relay that controls the fuel inj pump is in the relay block at the lower left of the dash. 6 in there total it is the one on the lower RH corner of the block. At least on mine it is. Pull it out and swap it with one of the others.
 
(quoted from post at 16:09:27 05/17/18) The relay that controls the fuel inj pump is in the relay block at the lower left of the dash. 6 in there total it is the one on the lower RH corner of the block. At least on mine it is. Pull it out and swap it with one of the others.

I’ll try to snap a pic tomorrow. Mine has 2 diodes and one relay all to the right of the fuse box. All of this is located behind the panel for the key switch.

Unless there are more somewhere I’m not seeing.
 
(quoted from post at 04:39:13 05/18/18) Item #1 in the parts dia. On the very lower left side.

http://jdpc.deere.com/pimages/LVP3/LVP3877________UN26NOV02.gif
Untitled URL Link

I found them today Mike.

I took several of them out cleaned them off and reinstalled them. So far the tractor is starting every time. I will have to wait a few days and make sure it continues to work. Hopefully it was just a loose connection.
 
Did you switch them into different spots ? If it acts up again swap them around. I have no idea what they all do as there is not too many electronics on those.
 
(quoted from post at 09:08:29 05/18/18) Did you switch them into different spots ? If it acts up again swap them around. I have no idea what they all do as there is not too many electronics on those.

I didn’t try swapping them around yet. I just seen how dusty they were so I tried just cleaning them up and blowing everything out. After that the tractor fired up every time.
 

I am having similar issues. Mine will turn over and crank as long as the key is in start position. Once I let it go it dies. I have replaced key switch 3 times. Every now and then it will stay running and be fine. Turn it off and will not crank. I have noticed that when it does this and won t crank, if I don t turn key to off position it will only spin over and not fire up. Any suggestions? I haven t looked at the relay switches yet. All fuses are good. Could it be the solenoid?
 
(quoted from post at 15:30:12 10/21/19)
I am having similar issues. Mine will turn over and crank as long as the key is in start position. Once I let it go it dies. I have replaced key switch 3 times. Every now and then it will stay running and be fine. Turn it off and will not crank. I have noticed that when it does this and won t crank, if I don t turn key to off position it will only spin over and not fire up. Any suggestions? I haven t looked at the relay switches yet. All fuses are good. Could it be the solenoid?

Mine ended up being a relay. My tractor would actually start and run once the relay was removed.
 
(quoted from post at 17:17:31 05/16/18) Shoot me your email, I have a PDF of the tech manual you're welcome to, has the wiring in it

Joe

I'm trying to troubleshoot my 5105 and ran across this. Do you still have the manual with the wiring and if so would you still be willing to share it? Thanks, Kyle
 

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