I'm looking into why the glow plugs on my skid steer aren't getting full power. The indicator doesn't glow like it used to but does get warm as it wouldn't start without them. It acts like 1 or 2 glow plugs aren't working. I was reading sometimes the glow plug indicator can get weak over time and changing it solves the problem. I've also read the ignition switch might not be letting full current go to the glow plug circuit. The starter needs the contacts cleaned occasionally in order to engage but maybe it's the ignition switch?? I did the change the ignition switch years ago but wondering if the ignition switch could be causing less power to the starting circuit as well as the glow plug circuit? It's a genuine Kubota ignition switch but I don't know if Kubota are known for short lived ignition switches?
What model is it?
It's an indirect injection V1902B in a Thomas T133. It runs great but a couple years ago the glow plug indicator stopped glowing and the glow plugs had to be left on longer. It seems to have got worse and in cold weather it's iffy it will start. I don't have power to plug it in and starting my generator would be even harder. Several sources have said Kubota/NGK glow plugs rarely burn out. Machine has about 4800 hours.
Glow plugs put a fairly strenuous load on a key switch. They can burn out if used quite often, which is the case in around Alberta for 6 months of the year. Take a multimeter set to DC Volts and stab the battery post of your key switch ( Terminal 30 ) with your Red meter lead, stab the glow plug terminal ( Terminal 17 or 19 Dependant on key switch and Relayed or non relayed Fuel solenoid )of the key switch with your other test lead while at the same time holding the glow plugs on. If your meter reads more than 0.5- 0.7 volts , the switch is faulty ( contacts inside are worn or arced ). This test is presuming that the wiring to the glow plugs themselves is okay. If there is no path to the glow plugs from the switch, then your meter reading will be super low. On some you can test with battery power direct to the glow plugs for short time period with DC clamp on recording whether or not the glow plugs used power. Probably need 2 people to do these tests. Test your switch first and send me a message about what meter recorded. Simon C
I'll see if there's a warmer day coming up. I found some other tests for ohms in a manual. Basically should have low readings on everything. The glow plugs have solid like buss bar connections so I think that's all good. It sounds like the ignition switch can get weak and limit power to the glow plugs?
You can only do an ohm test with power disconnected. Problem with that is that the weak contact will fail under load. Testing under load will locate the problem instantly. Forgot to say that Kubotas sometimes use Batt, Acc, Glow, ST, on the switch. Yours could be any one as may have been changed out before. Yes as you said the timer is suspect also if you have one. Too many variations on some models. Simon C
My machine has no timer or relays, strictly manual. The glow plugs are also turned on in the start position. I was reading that the starter draws enough current it limits the current to the glow plugs. 12 volts continuous will burn out the glow plugs. The glow plugs are rated as 10.5 volts. The glow plug indicator acts as a resister to lower the volts so the glow plugs won't burn out. On one forum someone said it's a variable resister that starts off at 12 volts and lowers the voltage the longer the glow plugs are on. I'm not sure but can certainly take some voltage measurements.
If your glow plugs are direct with no relay, you are correct, the voltage does drop the longer the glow plugs are on. That being said, the units with relays have way longer life of the key switch as the relay does more of the work. Your key may have bigger contacts inside for the glow plug feed, this may help but eventually they get corroded and arced. A test will tell the story. Simon C
The glow plugs are needed every cold start even if it's 30C outside so the contacts in the key switch get a good workout. I need to get some alligator clips for my multimeter so I can test the switch and indicator myself. I can't believe what test leads with alligator clips cost. I got the meter on sale for $25 down from $62 but test leads with alligator clips can cost as much or more. I saw some adaptors for $8 so will go that route. The original ignition switch went out so it wouldn't be wrong to suspect it could be the culprit. Maybe the ignition switch in addition to the GP indicator are both contributing to the problem. Originally I thought the glow plugs are easy to get at but I was wrong. You can't get at the side of the engine. I think I'd have to take the intake manifold and maybe some injector lines off to get at the glow plugs. I could do some resistance testing on the ends of the glow plugs though. There's a procedure to measure resistance on the connectors for GP's 1 and 2, then 2 and 3 etc. I think testing at the ignition switch should reveal the problem though. I can check the voltage at 1st glow plug where the power connects easy enough. It's the only one that's in the open. Can't thank you enough for mentioning the key switch could be bad. It could explain why it's getting harder and harder to start. Not sure when I can get out to test everything. We took in a very friendly stray cat and had it fixed so I need to stay home to look after him so he doesn't try to lick the area. He sure doesn't like the inflatable donut around his neck but it's better than a cone of shame.
I thought of something else I could try with the key switch out. I'm wondering if I took a short 10 or 12 gauge jumper wire and went from the power terminal to the glow plug terminal to see if the indicator glowed bypassing the switch? I could go direct to the indicator too.
Yes you could jumper as said and would know instantly that switch is the culprit. And yes my fluke Alligator clips of 2 sizes plus longer extension leads costed too much, but super handy when I am alone. I also made a set of 33 foot long extensions for some work I done. Hope you solve it. Simon C
If the GP indicator glowed after about 10 seconds (maybe a little more because it's colder) like it used to would make the switch the problem. When turning the key to start there is sometimes a delay before the starter engages which would also point to the switch. Hopefully I can get out to test things in the next few days.
If it is the switch I'm wondering if it's worth buying another OEM Kubota switch? It says made in Taiwan on the Kubota box so don't know if it's any better. It's a common switch with several aftermarket available on Amazon with good reviews. I'll see what a Kubota switch costs. If it's a crazy price I'll get an aftermarket. Have read of others having bad Kubota ignition switches.
I did some checking. The Kubota dealer that also sells Thomas parts wants $60 for a new ignition switch. A Kubota engine dealer that deals with generators and such sells the same switch for $50.××. With the issues I'm having and the fact I've replaced the switch before I'm just going to replace the switch and eliminate it as the problem. I think the key needing to be cycled a few times to engage the starter and/or there being a pause before the starter engages could be from a bad ignition switch. With a few issues that could be switch related I figure $50 is pretty reasonable to take the switch out of the equation. If the GP indicator proves to be bad it's $38.50. Still not a big expense. Much better than throwing new glow plugs in. I'd have to take the intake manifold off and some injector lines to get at the glow plugs but apparently Kubota GP's rarely burn out. Hopefully a new switch is all it needs.
Wanted to give an update so maybe it can help others. A mechanic friend changed the glow plugs and the indicator works again and the machine starts much better. He also adjusted the valves which weren't out very much. Less than 1/8 of a turn either way. The other thing he did was add a relay to the starting circuit to eliminate the multiple clicks it would sometimes do before the starter engaged. Should be like a new machine again.
Was using the skid steer today and noticed that it seems to turn over faster with the relay on the starter. Tested ohms on old glow plugs and 1 GP had a little bump on the tip. It was bad. The other 3 seemed good .7 and .6 ohms. but 1 was clearly cleaner than the other 2. I'm thinking they were getting weak and not burning all the carbon off. No black smoke when starting like it did with the old glow plugs. The engine seems to sound better too. Maybe from having the valves adjusted?? It's like a new machine.
Nothing like when the old girls fire right up. Have a good day! Simon C