Glow Plug Question

I'm having glow plug problems. These are 12 volt NJK plugs, three of them. When I have my key in the start position the plugs are running and draw the system down so far that the solenoid can't kick the starter in.

When I test the resistance of the plugs (all disconnected) at room temp they all read 0 ohms. So, then you hit the key your starting out with a dead short.

The resistance does go up, like it should, when they warm up. I've never seen plugs that start at zero though, usually they have a little resistance at all times.

Now what makes it interesting is when the switch is in the warm position there's far less a load, BUT in the warm position it includes a coil indicator in the dash. That would start the circuit out with a little resistance, which then allows the plugs to come online with out shorting the system out.

Am I making sense? What's up with these plugs?

K

sounds like the glow plugs should be connected to the circut that lights the coil and then should cut out when the starter is engaged as this would reduce the draw on the batteries during cranking.
Is the coil you speak of is it the light in the dash if so then the afore mentioned is the way it should be.You could also not have enough battery for the job too.

Glow plugs DO take a lot of "juice". Sounds like you need a new battery.

Glow plugs are all but a dead short; that's why they get so dam*ned hot.

You need a battery.

Allan

It's not the battery.

It has a brand new one, not only that but I get the same symptoms when I had it hooked up to the pretty substantial battery out of my Golf TDi. This little 3 cylinder 15HP Kubota Diesel is designed to start off a decent L/G battery...

I understand that a glow plug is pretty much a short, but to start at 0 resistance is putting a TON of load on the battery, so much so that I think it can't recover in time to kick the starter. Every plug I've ever tested, and admittedly that's not a ton, has some resistance at room temp.

I feel like I'm chasing a ghost but it just keeps point back to the plugs.

K

(quoted from post at 09:56:57 08/14/08) sounds like the glow plugs should be connected to the circut that lights the coil and then should cut out when the starter is engaged as this would reduce the draw on the batteries during cranking.
Is the coil you speak of is it the light in the dash if so then the afore mentioned is the way it should be.You could also not have enough battery for the job too.

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That would make sense to me too, but the wiring diagram clearly shows that the plugs are on while cranking.

This isn't a light, this is the real deal, a good old fashion glowing coil.

Thanks,

K

You've been having problems with these things a while now. You'd do yourself and your tractor a big favor by taking them completely out of the system and wiring them seperate wit their own circuit and switch (button). Get rid of the series they are in and run a wire straight from the battery positive to a pushbutton. then a wire from the button to each plug (3 wires). You can control everything and your problems will be gone.


Dave

(quoted from post at 12:53:58 08/14/08) You've been having problems with these things a while now. You'd do yourself and your tractor a big favor by taking them completely out of the system and wiring them seperate wit their own circuit and switch (button). Get rid of the series they are in and run a wire straight from the battery positive to a pushbutton. then a wire from the button to each plug (3 wires). You can control everything and your problems will be gone.


Dave

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I've thought about it, I just wanted to try and fix it first.

Really, all I would have to do is unhook the post on the switch that provides juice to the plugs while in the start position, it uses a separate post for the warm position.

I guess I'm just stubborn. :wink:

Measure for VD while the glow plugs are on. And while cranking.
It sounds like a high resistance cable(s) and/or a high resistance connection.
The chassis return cable from the battery should be bolted directly onto a starter mounting bolt.

(I guess I'm just stubborn. :wink:

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I went through a winter of starting fluid because I was intimidated by the wiring change. Finally ran out of either on a sunday with no stores open and made the change in less than half an hour.

Good Luck,



Dave

(quoted from post at 13:13:25 08/14/08) Measure for VD while the glow plugs are on. And while cranking.
It sounds like a high resistance cable(s) and/or a high resistance connection.
The chassis return cable from the battery should be bolted directly onto a starter mounting bolt.

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Where would you measure for the voltage drop, at the plugs?

K

0 ohms is a dead short. All glow plugs should have some resistance, around 1 ohm, but they're all different. If you've got a dead short or an open circuit, you've got a bad glow plug.

As said, the resistance of the glow plugs when cold is so low (close to 0 ohms, or a direct short) it is very unlikely you have the equipment to measure it. Put a few of them together, and it looks like a big short circuit, and if your battery is weak... or battery cables are old, wrong size or corroded.. My 88 7.3 IH Diesel in my F-250 starts in 1/2 second or less when it's 15 degrees out, but only when the glow plugs are all good, the batteries are both good, and the cable connections are good, and the starter is good!

Wayne

Across the battery posts. Between the battery post and cable clamp. Between cable end to cable end. Between cable to chassis. Between chassis return cable and starter body. Between starter body and the solenoid post going to starter. Measuring the voltage applied to the plugs at the last connection points.