Bypass the ignition switch for glow plugs

[Skuta]

Hi all,

First time poster so a quick introduction,

Australian, have driven plenty of tractors but first time owner, 2 acres to mow. Bought a B7100 hst with mmm. Overkill I know but.... who doesn't want to own a tractor??

So the guy I bought this from has had it about 2 years, engine sounds good, doesn't blow any funny coloured soot etc. But he has been using ether to start the engine because the glow plugs have never worked . Butchered wiring job which is completely confusing, so I figure I'd like to bypass the key switch and install a button on the dash to initiate the glow plugs.

Edit: I have already replaced the glow plugs, which didn't change anything, also from past experience with diesels there is always a "click" when initiating the glowplugs and another "click" when they come to temp.

Sorry if my research is slack but I'd like everyones help. I'm no auto electrician

Here is my current understanding

Battery > key switch > indicator coil > glow plugs.

what I'd like to do is

Battery > Push button > Indicator coil > glow plugs.

what I don't know is

1. Does the key switch have a solenoid (not sure if that's the right term) that cuts out if it goes over voltage (or some other safety feature).

2. do I need any fuses etc.

I understand that the coil acts as some kind of buffer that reduces the voltage to the glow plugs so they don't get over powered, so is that all I need in the circuit or am I missing something.

I am looking forward to the answers. This has been an extremely helpful forum to me so far and I appreciate the efforts that everyone has contributed to date.

 

[fast*st]

You are on the right track. power to the glow plugs should be battery - fuse - relay - glow plugs fuse might be optional if the current is over 30 amps.

On the starting side it should be battery - ign fuse - key switch - magic - light&solenoid

Now some tractors have a temperature sensor that cycles the glow plug relay/solenoid and the solenoid is the click.

I'd go backwards, check the glow plugs for proper resistance, likely a couple ohms to ground. trace the wiring harness back and find the relay, may be a square cube type or a small can type, Make sure the relay has power on the correct terminal and continuity to the glow plugs. The rest would be tracing back the trigger circuit. The light should be on the side/terminal of the relay that energizes the relay.

The magic box is likely an item that senses engine temp, outdoor temp and then watches for key power to turn on the relay for a specific time, it may be part of the dash cluster.

All you want to do is to put an alternate feed to the relay but first find and check all the fuses. My JD gator had a corroded fuse holder that was stopping the glow plugs from working.

 

[vtmbz]

I just rewired a b5100. There isnt any fancy electronics here: it was a heavy gauge (black with red stripe) straight from the ignition to the first glow plug. THere is also a coil under the dashboard wired in parallel ( that was just black) that provides a visual clue as to the gp status. THese older machines are not like diesel cars. I would say go for it. Just remember that Kubotas glow very slowly compared to other diesels for some reason, maybe the battery size?

 

[kubotasam]

A B7100 does not use a relay or any type of a timer. It is just the key switch that turns them on. The only trouble with changing from the key switch on the tractor to a push button is that the key switch also applies power to the glow plugs while cranking the engine. However when cranking the electricity does not flow through the indicator/resistor. The circuit relies on the voltage drop created when cranking to lower the 12volts of the battery down to the approximate 9 volts the glow plugs need. If you bypass the key switch with a push button the plugs will not heat while cranking. I do not know how this would affect starting. If you hold the button in while cranking the plugs would get a double reduction in voltage first from the voltage drop of cranking and then from the indicator/resistor. Once again I am not sure how this will effect starting. I guess anything is better than using ether.

 

[B7100]

Welcome to the forum skuta,do you have a wiring diagram for the B7100?
Dave

 

[kubotasam]

I just rewired a b5100. There isnt any fancy electronics here: it was a heavy gauge (black with red stripe) straight from the ignition to the first glow plug. THere is also a coil under the dashboard wired in parallel ( that was just black) that provides a visual clue as to the gp status. THese older machines are not like diesel cars. I would say go for it. Just remember that Kubotas glow very slowly compared to other diesels for some reason, maybe the battery size?

Unless the b5100 is different from a B7100 the indicator/resistor should be wired in series with the glow plugs not parallel. If it is wired in parallel the glow plugs will get full battery voltage.

 

[B7100]

Unless the b5100 is different from a B7100 the indicator/resistor should be wired in series with the glow plugs not parallel. If it is wired in parallel the glow plugs will get full battery voltage.

Looks the same wiring:
Dave

 

[Orange Tractors]

Skuta,

Get the glow plugs fixed, ether is not good for these little Kubota diesels; read some of the articles Service Dept Vic has written.

Here is a link to how I got my glow plugs working a couple of years ago: http://www.orangetractortalks.com/forums/showthread.php?t=4383&highlight=L175+glow+plug

All it really cost was a little time (since I already had a multimeter), and one crimp on butt connector. If you have to replace any wire, I would use 12 guage.

Robert

 

[Apogee]

Skuta,

I would strongly suggest replacing the key switch with the new original correct part and repairing the parts of the wiring harness that are hacked up. It will save you time and the tractor will work as designed with no issues.

In this case, the stock design is a very good one.

Just my $.02,

Steve

 

[Skuta]

Hi again, thanks everybody for your input. What I found yesterday was that the glow plug indicator was working, then the next time I tried it wasn't so I fiddled with it most of the afternoon and had a near restless night due to it. Got up this morning, it worked and worked again, then didn't. I was tearing my hair out until I noticed what the oil pressure light was doing.

It would dull slightly when I switched it then brighten when fully (till it can't turn any further) turned. Aha. Stop turning it all the way back, works like a charm. Again thanks for all your input, I hope this thread will now be useful to others.

 

[Apogee]

Skuta,

The reason that I recommended replacing the key switch is because I've seen quite a few bad ones. The weather gets to them.

For $25, replacing it ensures no future problems.

Glad you figured it out!

Steve