B1700 - new 30A fuse blew immediately on start

[tbronson]

Where are the glow plugs located?

The starting problem I described: Then it started to sometimes be dead on turning the key: after preheat, there was no click. Normally, preheat, then start and the engine would turn over. Sometimes, you'd just hear a click from around the start motor but no turnover. But what happened a few time before the fuse blowing was, no click at all. Lights go on at preheat, then at start, nothing at all.

 

[tbronson]

Deleted duplicated post.

 

[torch]

The glow plugs will be screwed into the head of the engine. Near the injectors. The injectors have pipes from the fuel pump, the glow plugs have wires from the ignition switch.

The 3 glow plugs are wired in parallel -- the wire probably hops from one to the next. The indicator is also in parallel with the plugs, but it is located in the dash and has a separate wire that splits off from the one to the plugs. Personally, I would suspect a problem with the indicator before the glow plugs, but they are all possibles. So is a chaffed wire between the ignition switch and the plugs or indicator.

Because they are in parallel, you can safely disconnect one plug a time and test (starting with the last one in the chain) but you will blow a fuse each time the bad one is still in circuit. Alternatively, you could use an ohmmeter to verify the resistance -- if any are at 0 ohms, then you've found the problem. I'm not sure what the normal resistance is supposed to be for your model, but it will be fairly low, probably between 1 and 5 ohms. If you find one at 1 ohm and two at 4 ohms, my bet would be the low one is the problem.

 

[torch]

I think there is an error in that wiring diagram. It makes more sense that the wire to the starter is fed from the secondary contacts on the starter solenoid.

Still, that should only receive power when the key is in the start position and the starter has engaged. And it would be getting power direct from the battery (through the solenoid), not through the fuse.

Looks like someone else realized there is a mistake in the wiring diagram. Kubota books has a correction:

http://www.kubotabooks.com/AutoIndex/index.php?dir=Tractor%20Owners%20Manuals/&file=B1700%2C%20B2100%2C%20B2400%20WSM%20stop%20solenoid%20wiring%20correction..pdf

 

[torch]

I'm not sure what the normal resistance is supposed to be for your model, but it will be fairly low, probably between 1 and 5 ohms. If you find one at 1 ohm and two at 4 ohms, my bet would be the low one is the problem.

Looking at the WSM from Kubota Books for a specific value, it appears the glow plug resistance is variable, based on temperature:

"This plug is a two-material type QGS (Quick Glow
System) for quick temperature rise, and has selfcontrolling
function as well as excellent durability.
The heater (4) connected in series to the heater (3),
which also functions as the resistor, is incorporated in
the sheath tube (1) of the super glow pi ug.
The resistance of this heater (3) cum resistor is
small when the temperature is low, while the
resistance becomes large when the temperature
rises.
Therefore, because sufficient current is flown to
the heater (4) during the initial period of
energization, the temperature rises quickly and the
resistance grows with the rise in the temperature of
the resistor, the flowing current is reduced to
prevent the heater (4) from being heated.
The ignition point is in the area of 2 to 3 mm
(0.079 to 0.118 in.) from the tip of the plug in order
to reduce its projection into the combustion
chamber."

 

[GreensvilleJay]

Ok, real easy test to do...

1) disconnect the wire that feeds power to the glow plugs at the first plug, so that ALL glow plugs are disconnected. Be sure the 'free' end is taped up.

2) turn key on to 'heat glowplug' .
a)If the fuse does NOT blow, then you have 1 or more bad glowplugs.
b) If the fuse does Blow, then the wire from the switch to the first plug is touching the chassis.

if a), disconnect all glowplugs and test each one.
if b), follow th ewire and look for where it's touching the chassis.

 

[torch]

b) If the fuse does Blow, then the wire from the switch to the first plug is touching the chassis.

OR

the short is in the indicator / indicator wiring.

 

[GreensvilleJay]

possibly, but the odds are a bad glowplug..or 2... My luck, all 3 would have failed.

if the indicator/wiring was shorted , it should have turned color or melted as it's not rated for 30 amps ( 20ga vs 10ga).

in any case, he needs to disconnect stuff after the switch.

 

[Dave_eng]

Looks like someone else realized there is a mistake in the wiring diagram. Kubota books has a correction:

http://www.kubotabooks.com/AutoIndex/index.php?dir=Tractor%20Owners%20Manuals/&file=B1700%2C%20B2100%2C%20B2400%20WSM%20stop%20solenoid%20wiring%20correction..pdf

I provided the correction note on Kubotabooks.com

Dave

 

[torch]

I should have guessed <lol>

 

[GreensvilleJay]

hmm. "" I then inserted a new fuse, turned the ignition switch to the preheat position, the indicator lights light up for about a second, and the fuse blew. ""

kinda rules out that 1/2 of the wiring... still looks like a bad( shorted) glowplug to me.

 

[torch]

Yes, the fact that the indicator starts to light up may suggest the indicator is OK. Or maybe that the indicator does not short out the system until it begins to heat up.

It is also possible that nothing is completely shorted. The glow plugs do have a fairly low resistance when good. It may be that one or more have just drifted beyond tolerance enough that the total draw of plugs and indicator exceeds 30 amps.

If that is in fact the case, it will make trouble shooting a bit more difficult. One might remove a good glow plug from the circuit and thereby lower the current draw enough to keep it below 30 amps, making it appear that the disconnected plug is bad.

Ideally, a current meter should be used to test each plug under full voltage rather than an ohmmeter or voltmeter. From the WSM description above, one should see a fairly high current draw initially, that quickly drops as the plug heats. But most digital multi-meters can only handle 10 amps or less before their own internal fuse blows.

 

[Dave_eng]

The GP indicator on the B1700 is not the glowing wire type.

It is a simple 1.7 watt light bulb

Dave

 

[torch]

Then it's got to be a glow plug, or the wire to the glow plugs.

 

[Maxtheutt]

I have a 2016 with this same problem. If I use the block heater to start it it's fine.

If I disconnect the hot wire to the glow plugs and put a test light between it and ground he fuse is fine and the glow plug light comes on.

What ended up being wrong with yours?

 

[torch]

I have a 2016 with this same problem. If I use the block heater to start it it's fine.

Do you mean the block heater only, no glow plugs at all, or do you mean the fuse doesn't blow using the glow plugs if the block heater was used first?

 

[Maxtheutt]

Do you mean the block heater only, no glow plugs at all, or do you mean the fuse doesn't blow using the glow plugs if the block heater was used first?

Sorry for the confusion. With the power wire to the plugs taped off and using the block heater to warm engine and not turning it to the preheat position on the switch it starts and runs fine.

It has a little over 100 hours and the first issue I had was the first glow plug in line started smoking real bad when I started it. When I took it out it looked like this.

 

[Maxtheutt]

I'm going to check their resistance now. I can't get kubota plugs until mid next week I need it this weekend.

 

[torch]

My guess is that you found your shorted plug already! ;-)

But check them all, just to be sure.

 

[Maxtheutt]

My guess is that you found your shorted plug already! ;-)

But check them all, just to be sure.

I get .8 - 1.0 - 1.0