GF1800e Electrical Issues

[elip001]

This is my first time posting here so I figure some background is due. I bought a Gf1800e about a year ago in rather rough shape so I anticipated problems. But in the first month of ownership I had a catastrophic engine failure that ultimately led to me having to buy a new block and fully rebuild the engine.

Now I have the block back in and the engine turned over fine but my battery didn’t have enough juice to get her moving so we charged it and upon attempting start again my fusible link burnt up on the wiring harness… I am pretty adamant about taking pictures but I admit this was not my finest work.

There is a starter relay that is not in any wiring schematic that I may have put the power wire straight to ground. My only problem is, that wire should be connected to the switch but I in no way can see where I would have had it connected, as well as I failed to image it.
Is there anyone out there that may have advice or possibly the same mower and could send me images of the wiring harness side of motor. Thanks in advance.

 

[North Idaho Wolfman]

Go to Kubotabooks.com and download the GF operators manual, it has the wiring diagram in it.

 

[Hugo Habicht]

A lot of people add a relay near the starter to avoid the fairly large solenoid currents through the start switch. This may explain that it's not in the schematics.

The start switch wire goes to the coil, other coil side to ground. The battery cable is going to the common contact of the relay and the solenoid is connected to the NO contact.

 

[elip001]

A lot of people add a relay near the starter to avoid the fairly large solenoid currents through the start switch. This may explain that it's not in the schematics.

The start switch wire goes to the coil, other coil side to ground. The battery cable is going to the common contact of the relay and the solenoid is connected to the NO contact.

So I have a wire diagram and maybe I’ll post it later today but the relay that is on the mower has PIN 85 and 86 flipped based on what I can tell, all diagrams of that relay are opposite of how mine is wired. Would this matter? I can't imagine so because it ran fine prior to pulling the engine. Just trying to rule out some culprits still.

 

[arml]

those old G series mowers were notorious for electrical problems. Maybe not so well publicized but the rest of the tractor is great, it's almost always electrical stuff that goes south on them

these require 12v to run (electric lift pump). They'll theoretically run without it but you'd have to feed the injection pump somehow..

starter "helper" relays are a godsend. Basically it's a 30a #87 relay installed in the starter solenoid circuit. Unplug the solenoid trigger wire (white?), and use that to trigger the relay on pin 86. Pin 87 goes to the starter. Pin 30 to the battery (or better/easier, on the starter's big wire that comes from the battery), and pin 85 goes to a good chassis ground. John Deere used to sell a kit specifically for mowers that had similar issues, part # was AM107421 but probably a new number now. It has the terminals already installed so all you do it plug it in and put the terminals where they belong. Super easy. BTW it only works with the "small" starters, some of the earlier G series used the "big" starter. The big starter had an external solenoid and had one large wire on the starter where the late starters were a gear reduction style starter with two wires (one large one small). If you have to replace a starter use the later one and wire it accordingly. That starter uses a lot less power to crank the engine and lasts nearly forever. Mine is still original-from 1994 IIRC.

run through the harness connectors and do a voltage drop test across all of them. Fix the bad ones. There is one below the steering wheel, underneath the tractor, that is almost always in bad shape. Hard to get at too but once you have the harness retention tab bent out of the way, you can get better access. The pins are often corroded. Similar for the voltage regulator connector under the steering wheel, behind the radiator. Almost always corroded if original. I've had to replace a bunch of those. On mine it was so bad that the wires were burnt, so I just removed the dynamo and put a regular 40A alternator on it that came off of a core BX24 engine from work (I worked at a dealer at the time). Not terribly hard to wire that in, and it bolts on-but you need to make sure to get the spacer (if you have seen a BX24 alternator setup, you know). There is a spacer on the pivot bolt and it is required. That or a stack of washers, it aligns the belt properly. It charges a little better at low speed (near idle) but it also needs a few wiring changes to be made at the regulator/rectifier in order to be done properly, and to run a good 10ga wire from the lug on the alternator to the starter, with a 50A slow-blow fuse inline. The only advantage is that it will charge a little better at lower engine speeds. The factory installed dynamo is plenty of charging power for the application though, and simpler. Not much goes wrong with them, maybe a bearing once in a while and they are simple to rebuild.

 

[Russell King]

Here is a diagram for how the helper relay is supposed to be wired just to make it easy.
Although it is different than the words above by @arml. I have not messed with relays that much so can’t comment about what happens if they are done backwards but I would assume that they either work the same or not at all.

 

[Hugo Habicht]

So I have a wire diagram and maybe I’ll post it later today but the relay that is on the mower has PIN 85 and 86 flipped based on what I can tell, all diagrams of that relay are opposite of how mine is wired. Would this matter? I can't imagine so because it ran fine prior to pulling the engine. Just trying to rule out some culprits still.

85 and 86 are typically the coil pins. It would not matter if those two are swapped compare to the schematics you have.

Is it possible that you squeezed one of the wires (from the starter?) and shorted it to chassis / ground when you swapped the engine?

 

[elip001]

85 and 86 are typically the coil pins. It would not matter if those two are swapped compare to the schematics you have.

Is it possible that you squeezed one of the wires (from the starter?) and shorted it to chassis / ground when you swapped the engine?

It could be, but when I was attempting the first start it didn't short to ground and I haven't really messed with it between then and charging the battery, only thing of note from first attempt was the battery couldn't turn engine hard enough for compression near as I could tell.

Checked the glow plugs prior to second attempt to make sure they were any good and they all were but when we went to start the fusible line burnt up immediately. And I don't recall the crimp having direct contact to the block last night but I will be checking that tonight.

If that is not the case though is it possible I didn't have this problem with the near dead battery because voltage was low enough not to cause a ground fault?

 

[Hugo Habicht]

Yes, it would be possible that a very weak battery did not blow the fusible link despite a short. The current supplied by the battery into the short may have been too small to melt the link.