Glow Plug Question

I know I have a problem, I just need some help understanding what I need to do it fix it.

I have a little Kubota D600-B engine. When the the glow plugs are on they short out the battery, the amp meter pegs to the discharge side. This is a big problem since when the key is in the start position it's not only running the starter it's also running the plugs.

I used my multi-meter to confirm that there is zero resistance between the where the lead connects and ground (on all three plugs, all disconnected).

So, I get a dead short, that's not right. These plugs were all replaced when I rebuilt the engine last year. Could be be three bad plugs or is there something else going on?

Thanks,

K

'Course it's a dead short. That's what makes 'em get hot.

Get a bigger battery.

Allan

Yes but...I've never seen plugs that had zero resistance. Seem like the others I've tested (mainly VW TDIs) have always been around an ohm or so.

Seems like you wouldn't want them to be closed (short) or open (big time resistance).

I would love to get a bigger battery but I can't fit one under the hood. That and I know of other machines that use the same exact or even lesser (less CCA) batteries in the same application.

When the plugs are on the voltage drops to the high 9s to low 10s, that's quite a drop off from 12+ volts with no load. I've also tried a new battery.

K

Hello kopeck.
Take the leads off all of the glow plugs and test them one at the time.
Read the resistance , there has to be some, if it is zero, that plug is toast!.Look at the fuse and see what size it is. Electrical circuits are fuse 50% above the working amps. 10 amp circuit 15 amp fuse.
The glow plugs should not be drawing the battery down as much as you describe.
Ohms law states that E = I x R. E= volts; I= amps; R=resistance. If you have a 30a fuse for the circuit you should be drawing about 20 amps. 12V / 20A = .06 ohms would be the total circuit resistance.If you have six glow plugs that means
1 ohm each.
Guido.

I will agree with Allan, These will look like a short. Maybe the Starter is dragging, or a connection is poor. There should be a specification in the book.
Are the plugs suppsed to b fed through the mp gauge? JimN

(quoted from post at 18:11:21 06/11/08) Hello kopeck.
Take the leads off all of the glow plugs and test them one at the time.
Read the resistance , there has to be some, if it is zero, that plug is toast!.Look at the fuse and see what size it is. Electrical circuits are fuse 50% above the working amps. 10 amp circuit 15 amp fuse.
The glow plugs should not be drawing the battery down as much as you describe.
Ohms law states that E = I x R. E= volts; I= amps; R=resistance. If you have a 30a fuse for the circuit you should be drawing about 20 amps. 12V / 20A = .06 ohms would be the total circuit resistance.If you have six glow plugs that means
1 ohm each.
Guido.

Click to expand...

Thanks Guido,

The leads where all disconnected when I tested the plugs. There's no fuse, there is a breaker though. It's never kicked as far as I know.

It's weird that they're all gone, especially when they're all new.

Something must have toasted them.

K

(quoted from post at 18:15:58 06/11/08) I will agree with Allan, These will look like a short. Maybe the Starter is dragging, or a connection is poor. There should be a specification in the book.
Are the plugs suppsed to b fed through the mp gauge? JimN

Click to expand...

I've been messing with this for a while now, I've eliminated everything else, it's the glow plugs. Remove them from the circuit and everything works just like you would expect.

Zero resistance is a short.

K

have you tried one out of the engine with a jumper ground, and the others disconnected?
JimN

Are they correct for application?

They will have a voltage rating. Most systems are parallel these days but many were series wired in earlier years of diesel technology. Landrovers had a large ballast resistor in circuit as well.

Each glow plug should visibly get hot if tried outside the engine and they should, all three, heat evenly as a group. Typically modern ones are 50 - 100 watts so should draw about 4 - 8 amps. The resistance will, of course, rise as they heat up to limit the current.

If they were a dead short the fuse, or the wiring, would have melted by now, so that is clearly NOT the case!!.

If wired the parallel and should be series, they would be toast in short time.

I think your battery or starter or wiring/connections are poor somewhere, or you have the wrong plugs installed. Or the engine is too tight. First do a simple check on the glow plugs and then look for the real problem.

If they draw 8 amps each their resistance when hot will be about 1.5 Ohms.

Regards, RAB

(quoted from post at 16:55:37 06/11/08) I know I have a problem, I just need some help understanding what I need to do it fix it.

I have a little Kubota D600-B engine. When the the glow plugs are on they short out the battery, the amp meter pegs to the discharge side. This is a big problem since when the key is in the start position it's not only running the starter it's also running the plugs.

I used my multi-meter to confirm that there is zero resistance between the where the lead connects and ground (on all three plugs, all disconnected).

So, I get a dead short, that's not right. These plugs were all replaced when I rebuilt the engine last year. Could be be three bad plugs or is there something else going on?

Thanks,

K

Click to expand...

If you connect a multimeter between a ground and the end where the wire connects and have continuity, your plug should work. If it's not the correct plug for the application, that's a different story. If you're using the VW TDI plugs in place of the correct ones without modifying anything else (wiring), your problem is there. Not saying that is your case, but it sounds too familiar. Why?

My 3cyl IHC takes GP's that cost about $65 each when TDI ones cost about $3.50. I bought some home-made adapters that someone made to use the TDI's in my tractor. Tried using the same setup as far as wiring, and was only missing the marshmallows. That modification requires the GP's to be on thier own heavy gauge circuit. Simple as a wire from the battery to a 3 way splitter, and the same size wire from the splitter to each plug (no series), with a pushbutton switch. No meters, just count seconds (5-10 seconds is plenty.
Hope this helps.

Dave

They would be wired in a parallel circuit, that is the feed wire goes on the post of the first GP, then there's a jumper that goes from 1 to 2, then 2 to 3, obviously the ground is the head.

I've been trough this system a few times trying to figure out what's going on. I can't find any other shorts. All you have to do is remove the feed wire from the first GP and everything works. The only other thing I could think of is if the GP indicator (coil that heats up, not the newer light) is some how at fault. There's two poles on the switch for the GPs, one goes to the indicator then back to the switch on the other pole that's also connected to the plugs, you can see it what I'm talking about by clicking http://www.cubfaq.com/wiringdiagrams/782D.jpg.

These are the proper plugs, brand new out of the box a year ago. I think they're champions.

I can try to put my muti meter in the circuit and figure out how many amps are being drawn.

Thanks,

K

What"s in there? Fast acting, low ohm 6V plugs that require a controller. Or slow 12V plugs that can be left connected to 12V without melting?
Three ^v or even 12V plugs in parallel would look like a dead short to most pocket multimeters.

(quoted from post at 10:34:22 06/12/08) What"s in there? Fast acting, low ohm 6V plugs that require a controller. Or slow 12V plugs that can be left connected to 12V without melting?
Three ^v or even 12V plugs in parallel would look like a dead short to most pocket multimeters.

Click to expand...

12 volts plugs. Nothing fancy, the switch just turn on the power to the plugs.

I tested them (resistance) individually, not all hooked together.

K

Time to bring this thread back to life.

Today I really dug into the the problem. I bypassed all the safety switches with the same results.

For the fun of it (really, this was semi planned) I pulled the battery out of my VW Golf TDi (TDi = Diesel for those not up on the Volkswagen terminology) and hooked 'er right up, and guess what, same problem! So those that think I need a bigger battery, well, that's a pretty big battery!

Same old story, eliminate the glow plugs from the circuit and the starter spins over like crazy, plug them in and all I get is a little *click*.

There's no shorts between the key and the plugs so I'm kind of at a lost right now.

Could something be up with the key switch maybe?

Do I need a new tractor?

K