How can I get my Kubota diesel to start better?

[legman]

I've had several skid loader and now have an S150 and a 743, that I just bought. All the newer stuff I've been in starts (in summer months) at the tweak of the key, but this 743 wants to be glow-plugged almost every time I start it. I'm not sensing that there's any fuel drain back problem, because I don't have to shoot it with ether, so is it possible that the injector timing just needs to be set, or is there something more wrong with it? Any help?

 

[Drhandy]

Has far as the glow plugs seems the temp sensor is defective and not sensing the right ambient temp. if you are sure that the fuel is up to pressure then ,there are a couple of things that could be causing the hard start. Mine starts after about 10 to 15 seconds after the key is turned in summer and winter after glow plus. Does it smoke. If so I would check compression and injectors. Pump timing could be one problem. Check to see it the bleed valve on the injector return line is close and not leaking that cause the pump to over come the leak before can be raised high enough to open injectors at start .

 

[frogfarmer]

Has far as the glow plugs seems the temp sensor is defective and not sensing the right ambient temp. if you are sure that the fuel is up to pressure then ,there are a couple of things that could be causing the hard start. Mine starts after about 10 to 15 seconds after the key is turned in summer and winter after glow plus. Does it smoke. If so I would check compression and injectors. Pump timing could be one problem. Check to see it the bleed valve on the injector return line is close and not leaking that cause the pump to over come the leak before can be raised high enough to open injectors at start .

Sounds like a classic glow plug problem. Check for current at the plugs; all the plugs. If the current is there pull the plugs and make sure they turn red when energized. When everything is right that motor should start before it makes a full round with the starter.

 

[legman]

Sounds like a classic glow plug problem. Check for current at the plugs; all the plugs. If the current is there pull the plugs and make sure they turn red when energized. When everything is right that motor should start before it makes a full round with the starter.

Why would this be a glow plug issue? If the machine is being started in hot weather and NOT using the glow plug feature the engine should start WITHOUT them. My S150 starts with a tweak of the key, WITHOUT hitting the glow plugs and so did my New Holland LS170. But maybe you know more about this than I do! When a 743 is being started normally is there some sort of circuit that activates the glow plugs, even thought I'm not holding the key in reverse to turn them on? I always thought it was necessary to turn them on manually if they were needed?

 

[Tazza]

Why would this be a glow plug issue? If the machine is being started in hot weather and NOT using the glow plug feature the engine should start WITHOUT them. My S150 starts with a tweak of the key, WITHOUT hitting the glow plugs and so did my New Holland LS170. But maybe you know more about this than I do! When a 743 is being started normally is there some sort of circuit that activates the glow plugs, even thought I'm not holding the key in reverse to turn them on? I always thought it was necessary to turn them on manually if they were needed?

For starters, the two engines may be made by the same company, but they are NOT the same. Your S150 may be direct injection instead of the 743 that is indirect. Some did use indirect injection too but the design of the pre-combustion chamber is different. The newer style is designed to burn the fuel better. The glow plugs are different, they may get to temperature faster. Even in warm weather, i'd suspect it will still give a bit of a glow, just not the ten second count down the display shows.
The 743 may have lower compression due to its age which will make it harder to start.
I have always found V1702 engines needed a glow, even on a warm day. They would start, but it needed a good crank and would blow a fair bit of white smoke till it caught.
The engines are the same, but different enough to make one easier to start than the other.
Hopefully that gives you some insight into why the 743 is harder to start.

 

[mrfixitpaul]

For starters, the two engines may be made by the same company, but they are NOT the same. Your S150 may be direct injection instead of the 743 that is indirect. Some did use indirect injection too but the design of the pre-combustion chamber is different. The newer style is designed to burn the fuel better. The glow plugs are different, they may get to temperature faster. Even in warm weather, i'd suspect it will still give a bit of a glow, just not the ten second count down the display shows.
The 743 may have lower compression due to its age which will make it harder to start.
I have always found V1702 engines needed a glow, even on a warm day. They would start, but it needed a good crank and would blow a fair bit of white smoke till it caught.
The engines are the same, but different enough to make one easier to start than the other.
Hopefully that gives you some insight into why the 743 is harder to start.

How many hours on the 743? Usually after 2000-3000 they get hard to start due to engine wear.

 

[frogfarmer]

Why would this be a glow plug issue? If the machine is being started in hot weather and NOT using the glow plug feature the engine should start WITHOUT them. My S150 starts with a tweak of the key, WITHOUT hitting the glow plugs and so did my New Holland LS170. But maybe you know more about this than I do! When a 743 is being started normally is there some sort of circuit that activates the glow plugs, even thought I'm not holding the key in reverse to turn them on? I always thought it was necessary to turn them on manually if they were needed?

legman as tazza stated the motors are completely different. Your 743 will have two solenoids one for the start circuit and one for the glow circuit. Key to the left and the glow circuit is active. Key to the right and the start circuit as well as glow circuit is active. Bobcat used an inline diode to activate one but not the other. Many owners and poor techs will eliminate the diode and then you have no glow circuit on start. The motor was designed for glow plug heat on every start. The solenoids are behind a plate in the engine bay and you may not realize they are there. These solenoids are not the solenoid connected to the starter. As before the glow plug tips in the pre-combustion chamber must glow red for proper operation. Kubota builds a very dependable engine but the glow plugs are prone to an early death.

 

[busa4]

hello legman. i need your help. just picked up a 743 and the engine bay wiring is a mess. can you snap me some pictures of the wiring going to the starter solenoid and the two relays on the left side? my email is [email protected] thanks and much appreciated.. joe

 

[frogfarmer]

hello legman. i need your help. just picked up a 743 and the engine bay wiring is a mess. can you snap me some pictures of the wiring going to the starter solenoid and the two relays on the left side? my email is [email protected] thanks and much appreciated.. joe

busa4 Oldmachinist has the manuals for that unit online. I haven't looked but the wiring diagram should be in the service manual. My paper manuals have clear and easy to understand diagrams. Send a manual request and someone will have what you need.

 

[Tazza]

busa4 Oldmachinist has the manuals for that unit online. I haven't looked but the wiring diagram should be in the service manual. My paper manuals have clear and easy to understand diagrams. Send a manual request and someone will have what you need.

The wiring is very simple.
One relay is for the starter the other is for glow. Turn the key and work oit what one clicks for glow and what is for start, wire it accordingly. Thankfully they are very simple to wire up.
Even if you use a test light to see what one has power going to it to work out what one is what.

 

[frogfarmer]

The wiring is very simple.
One relay is for the starter the other is for glow. Turn the key and work oit what one clicks for glow and what is for start, wire it accordingly. Thankfully they are very simple to wire up.
Even if you use a test light to see what one has power going to it to work out what one is what.

If everything is right both relays will energize in the start position and only one in the glow position. A diode lets this happen and if the wiring is destroyed the diode is probably gone. The diode is in a jumper from the start relay to the glow relay. It stops flow from the Glow relay to the start relay in the Glow only position of the key switch. In the start position the jumper alows flow to actuate the glow relay when the start relay is energized. Hope this helps.

 

[Tazza]

If everything is right both relays will energize in the start position and only one in the glow position. A diode lets this happen and if the wiring is destroyed the diode is probably gone. The diode is in a jumper from the start relay to the glow relay. It stops flow from the Glow relay to the start relay in the Glow only position of the key switch. In the start position the jumper alows flow to actuate the glow relay when the start relay is energized. Hope this helps.

I did't think they all had this, i wired mine up that way though Its not enough to start by cranking alone, the plugs take too long to warm up. But it does keep them hot when you switch from glow to start.

 

[frogfarmer]

I did't think they all had this, i wired mine up that way though Its not enough to start by cranking alone, the plugs take too long to warm up. But it does keep them hot when you switch from glow to start.

Tazza you got it the whole idea was to keep the plugs hot during cranking. Every unit I have come across that was unmolested has been set up this way. I by no means have seen every variation and some may be different but it only makes for good engineering to keep the plugs hot.

 

[Tazza]

Tazza you got it the whole idea was to keep the plugs hot during cranking. Every unit I have come across that was unmolested has been set up this way. I by no means have seen every variation and some may be different but it only makes for good engineering to keep the plugs hot.

Thats just it, i think all the machines i have had were previously fiddled with.
I was told that its normal for a glow plug on some cars/trucks to operate still after they are running. Its only for a short time and lower duty cycle but it was to keep the heat up for emission control untill the enging had warmed up enough for them to not be required.