JD 870 will not start, again....****RESOLVED****

[JS415]

I have previously posted in a thread where my 870 would not start. Would not crank, nothing. In that case I finally found that the 3A fuse was blown.

I replaced the fuse and all has been well all winter, until today.

I started it this morning, all was good. Parked it about 3 hours. Went back out, it cranked for maybe 2 seconds, then was completely dead. All lights are on, dash is good, everything works, but will not crank. Also, when I turn the key, I do not hear the usual click of the fuel solenoid opening.

It will crank if I jumper from the battery to the starter solenoid. Will not start though, since no fuel coming to it.

I checked the same fuse, and sure enough, it was blown. I replaced it, blown again, instantly.

Repeated this several times with higher amperage fuses, and it continues to blow the very second I turn the key. Quick and violent blowing.

Almost like a dead short in something. What could possibly be shorted? Any ideas what to try and troubleshoot to figure out which device is bad?

Fuel solenoid bad, safety switch somewhere?

Thanks for any ideas and suggestions.

Jerry

 

[JS415]

I tried a little troubleshooting. I disconnected the fuel solenoid, and the 2 relays directly under the steering wheel. I did these one at a time.

After each of these were disconnected, it tried a new fuse. It blew each fuse, each time. So it must not be one of those 3 items causing the issue.

I have attached a picture of the fuse box cover. It is the 3A fuse on the top left that is blowing.

All I can find on the internet is that this fuse goes to the "control box", whatever that is.

Any ideas??

 

[JS415]

I used a small piece of wood and wedged open the fuel solenoid. Jumped the starter and moved the tractor back into the barn. It runs great, nice and smooth, started right up, but something is making that 3A fuse blow instantly.......

Jerry

 

[grsthegreat]

ya, thats the symbol for the pto


that fuse protects the following
Safety System Fuse (3 Amp)—Protects the Seat
Safety Circuit, PTO Safety Circuit, Transmission Neutral
Circuit and Time Delay Control Module.

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the link above has some wiring diagrams

 

[beenthere]

Instead of putting in good fuses to just blow again, rig up a 12v light bulb to insert into the fuse slot. If/when there is a short, the bulb will be lit. Then you can play with the plug/unplug, move wires about, and hopefully zero in on the location of the short. Saves a lot on fuses.

 

[JS415]

I found the problem this morning. I used my multimeter and was able to verify that there was a dead short between the bottom conductor of the fuse that was blowing and the frame of the tractor.

I figured a wire had been pinched somewhere. I searched and search all under and around the seat, frame, etc., and could not find anything.

I went back to the fuse block and started looking at the wires coming from the rear of it. On the left hand side, the wire that went to that particular fuse, was wedged between the fuse block itself, and the metal frame that holds the fuse block in place.

I removed the block, and sure enough, there was a pinch in the wire, and a good portion of the conductors showing.

These conductors were touching the frame and shorting out. This has been this way since I bought the tractor new in 1996. I've never had any work done on it. I'm amazed it took this long to finally short itself out.

Back to working perfect and all is good now.

Pictures attached.

 

[grsthegreat]

Glad to hear you found the problem

 

[MoKelly]

I admire your perseverance. This will probably help someone else down the road.

MoKelly