Cockpit instrument panel works sometimes

[KWKloeber]

 I said below no need to remove plugs.

Loosen the thumbscrew in each w/a thin tip screwdriver, remove the common wire.
Measure and record the resistance from each tip to the engine block to see if any are shorted or drawing more than spec.
OEM glow plugs are cheap. Inexpensive insurance.

[ChrisW]

Sorry, when I said I removed glow plugs I didn't mean that I removed the actual glow plug from the engine, just removed it from the circuit by disconnecting the wire on top. Yes, I understand what you mean now and will try that.

[ChrisW]

I said below no need to remove plugs.

Loosen the thumbscrew in each w/a thin tip screwdriver, remove the common wire.
Measure and record the resistance from each tip to the engine block to see if any are shorted or drawing more than spec.
OEM glow plugs are cheap. Inexpensive insurance.

For each glow plug, doing the above, I measured 1 ohm.  To me that's not great, but I'm no electrician.

Also I lost lost one of those thumbscrews. Whoever designed this engine had tiny hands and delicate little fingers or is a sadist. Can I buy replacements for those?

[KWKloeber]

Chris

ok that's a problem. Unsure how accurate your meter is, but....
1 ohm is why you're blowing a fuse. 
The spec is 1.6 ohms (+/-) cold.
You probably get ~11 volts at the plug so 11/1.6=6.8 x 3 = 20.4 amp.
That's per Kubota's shop manual, not per NGK.  I'm not sure that I have ever seen a resistance spec from the plug mfgr.    The Universal wiring schematic says 6a each.

I don't recall (~15 yrs ago) but I'm sure my new plugs probably came complete (maybe w/ a hex nut.)
If you stop by a diesel shop they probably have a few nuts laying in a trash basket, or get an M4 metric nut at the hardware store.

A new set (NGK Y-103V) is 15 bucks at Rock Auto.  Don't effaround w/ them.

I will repeat myself deja vous all over again - you DON'T want to ('er, I mean shouldn't) install that dumb relay or worse, a starting solenoid.  NGK Y-103V are 10.5v glow plugs.  Not meant to have 12v 0r 13.5v or maybe 14+ v (if your shore charger is on) applied to them.  Wire resistance to the panel and back is a GOOD thing.
Or "save" 10 seconds preheating, and add 3 more unnecessary connections and a relay that can fail, to the starting circuit.  I haven't heard (read from) anyone who can defend installing that damn thing, other than they can let go of the button 10 seconds sooner. If you do install a relay, get a socket side that can be mounted, and the relay itself a plug-in that isn't mounted (so you can quickly pop it out/in if it burns out.)

-k

[ChrisW]

Chris

ok that's a problem. Unsure how accurate your meter is, but....
1 ohm is why you're blowing a fuse. 
The spec is 1.6 ohms (+/-) cold.
You probably get ~11 volts at the plug so 11/1.6=6.8 x 3 = 20.4 amp.
That's per Kubota's shop manual, not per NGK.  I'm not sure that I have ever seen a resistance spec from the plug mfgr.    The Universal wiring schematic says 6a each.

I don't recall (~15 yrs ago) but I'm sure my new plugs probably came complete (maybe w/ a hex nut.)
If you stop by a diesel shop they probably have a few nuts laying in a trash basket, or get an M4 metric nut at the hardware store.

A new set (NGK Y-103V) is 15 bucks at Rock Auto.  Don't effaround w/ them.

I will repeat myself deja vous all over again - you DON'T want to ('er, I mean shouldn't) install that dumb relay or worse, a starting solenoid.  NGK Y-103V are 10.5v glow plugs.  Not meant to have 12v 0r 13.5v or maybe 14+ v (if your shore charger is on) applied to them.  Wire resistance to the panel and back is a GOOD thing.
Or "save" 10 seconds preheating, and add 3 more unnecessary connections and a relay that can fail, to the starting circuit.  I haven't heard (read from) anyone who can defend installing that damn thing, other than they can let go of the button 10 seconds sooner. If you do install a relay, get a socket side that can be mounted, and the relay itself a plug-in that isn't mounted (so you can quickly pop it out/in if it burns out.)

-k

I got the glow plugs in the mail yesterday.  Part number "NGK 2031".  It has "Y-103V" on the box.  I tested the resistance of one of them with three different multi-meters and am getting about 1 ohm.

I don't know if I should take the time to install them in the engine to see what happens or not.

I see in the engine manual the 30 amp fuse, just like you said, so I don't understand.  If the volts are only 10.5 with 1ohm, with 3 glow plugs shouldn't that be 31.5 amps?  And like you said, it could be more since the voltage drop probably isn't enough to bring it down to 10.5V.

What do you think?

[KWKloeber]

Chris,

As I said the spec is 1.6 ohms (+/-) cold.
Maybe NGK has changed their plugs????

Try a 35a fuse. ANY fuse is better than no fuse - it's not so much that you're going to melt the cable, it's in case there's a short and even a 40a will pop in that case.

W/ the preheat circuit with terminals, switch, etc is probably like 1/10 ohm.  Test it and see how close my guess is?

-k

[ChrisW]

Chris,

As I said the spec is 1.6 ohms (+/-) cold.
Maybe NGK has changed their plugs????

Try a 35a fuse. ANY fuse is better than no fuse - it's not so much that you're going to melt the cable, it's in case there's a short and even a 40a will pop in that case.

W/ the preheat circuit with terminals, switch, etc is probably like 1/10 ohm.  Test it and see how close my guess is?

-k

I installed one of the new glow plugs, disconnected the power to the other two and turned the preheat on.  I measured about 11 amps.  I think what I will do is just use a bigger fuse.

Thanks so much for the help.