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2nd mate
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42 Posts
Discussion Starter #1
Hello,

I have a Kubota 3 cyl 21 hp.
The filters and oil are all changed as it should be.

The problem is that I can't start the engine.
It turns over nicely, but the glowplugs don't stay on long enough.

When I measure the voltage on the glowplugs, it reads 10 or 11 volt and dropping slowly. The relais shuts off, before i release the glowplug switch.

The starting battery reads 12,7 volt at rest and 10 volts when glowing or cranking.
This starting battery is charged by a good 4-stage charger from shorepower.

Do I need new battery or new relais or is it someting else?
 

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2,376 Posts
Hey,

If your starting battery is at 10 volts when USED (glow plugs and / or cranking the engine) either it is discharged or just dead. If it reads 12.7 at rest I think the battery is just shot. Do you know how old it is?

Can you 'borrow' a known good battery and use that as a test?

Good luck,
Barry
 

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Tartan 27' owner
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5,242 Posts
Also, do they have wd40 in Belgium?
You can use wd40 as a starting fluid with diesel engines.
Squirt some on the air intake before cranking.
Ether is not recommended for starting diesels.
 

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Have a go and DIY .....
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109 Posts
Hello,

I have a Kubota 3 cyl 21 hp.
The filters and oil are all changed as it should be.

The problem is that I can't start the engine.
It turns over nicely, but the glowplugs don't stay on long enough.

When I measure the voltage on the glowplugs, it reads 10 or 11 volt and dropping slowly. The relais shuts off, before i release the glowplug switch.

The starting battery reads 12,7 volt at rest and 10 volts when glowing or cranking.
This starting battery is charged by a good 4-stage charger from shorepower.

Do I need new battery or new relais or is it someting else?
Just had the same problem .
Lucky for me the engine has not yet been fitted .
But it turned out to be the fuel cutoff solenoid.
Seems if it is not working the power can not pull back a small pin.
Hence the pin stays out and stops the fuel starting the engine..
It was Not easy to find that out I can tell you...
 

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2,063 Posts
But it turned out to be the fuel cutoff solenoid.
I think macwester is on the mark here. If you have a fuel cutoff valve (many small diesels do but many don't...I'm not familiar with Kubota) and the voltage drops too low the fuel cutoff solenoid will not stay open to allow fuel to flow.

If the voltage starts at 12.7V with no load your battery it needs an equalizing charge at a minimum. If after equalizing the battery the open circuit voltage is still less than 13V or if the voltage is higher but falls rapidly when the glow plug circuit is energized you need a new battery.

Good luck.
 

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2,376 Posts
Hey,

I have a 3 cyl Universal Diesel on my boat, which is based on a Kubota tractor engine. The engine stop lever is mechanical, there is no solenoid involved.
 

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██▓▓▒▒░&
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13,645 Posts
12.7 volts at rest, 24 hours since the last charging, would be a 100% perfectly good "12" volt battery.

"It turns over nicely" seems to confirm this.
 

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4,831 Posts
Did you change the fuel filters? If you did and got air in and didn't bleed the system, it won't start.
 

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2nd mate
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42 Posts
Discussion Starter #10
Fuel is clear of air, seems OK.
i tried my house battery to start the engine, but the effect was the same: the reading voltage on glowplugs is only 10,5 V (maybe the house battery is also shot...)
I also bridged the glow plug relais manually, but the effect was the same.
I tried also the WD40, to no avail.

I ordered a new battery to sum things up :)
 

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3,184 Posts
10V is a healthy voltage while cranking. It is not such a healthy voltage while just the glow plugs are on.

I have a 3 cyl Kubota, and I can tell you with hot glow plugs and a healthy battery it will start up as soon as I think about touching the start button.

You don't need starter fluid, or a new battery (given that you say it turns over healthily, you need to methodically figure out what the problem is. You need compression, fuel, air, and maybe some heat, and it will start. Find out which one is missing.

The clue might be in the history. What did you do last?

You say there is no air in the fuel. How do you KNOW? I suggest bleeding from the screw right on the fuel injection pump body. This would be my very first step if my engine turned over but did not start.
 

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2nd mate
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42 Posts
Discussion Starter #12
I have bled the screw right next to the injector body, the flow is nice constant and not bubbling.

The voltage is 10V when heating the three glow plugs, when starting only it is a bit higher.

The last thing i did on the boat was fuddling around with the start panel (rebedding), but electrically i see everything is working.

I wil wait for my new battery for now.
 

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2nd mate
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42 Posts
Discussion Starter #13
I got a new battery.
I managed to start the engine by using a thick jumperwire from the pos battery pole to the glowplugs. WD 40 helped also :)
The startmotor seems to be normal.

BUT: if i try use the glowplugs the normal way, the relais switches off after 20 seconds...
Its a relais from Ford cars rated for 70 amps.

I will order a new relais online.
 

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██▓▓▒▒░&
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bart, it sounds like your Ford relay is a starter motor relay. Those normally do not have any type of timer or thermal overload protection built into them, so if it is switching off there may be another component that is cutting off power. A thermal breaker or a timer perhaps?
 

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I have a lingering doubt over the glowplugs themselves... 20s of heating should be enough to get the engine started. They do have a tendency to age and become less and less effective... if problems persist I would consider replacing them. The price should be reasonable from a Kubota parts supplier (not a marine supplier)
 

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1. Release the glow plug button before you hit the start button. Do NOT hold them both down at the same time.

2. You may have a glow plug solenoid (relay) installed. For your M25 engine, it is an aftermarket addition since they did not come with the engines. I installed one on our boat, it's a cheap Ford solenoid. You might be interested in this and other subjects in our C34 Critical Upgrades: CRITICAL UPGRADES - DO THESE OR ELSE!!!

The glow plug solenoids are here: Faster, More Efficient Glow Plug Heating with a Solenoid - C34
 

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I got a new battery.
I managed to start the engine by using a thick jumperwire from the pos battery pole to the glowplugs. WD 40 helped also :)
The startmotor seems to be normal.

BUT: if i try use the glowplugs the normal way, the relais switches off after 20 seconds...
Its a relais from Ford cars rated for 70 amps.

I will order a new relais online.
I had a VW diesel. IIRC, the glow plug relay would hold for about 10 seconds and then shut off and stay off for a minute or so. As we were often in very cold weather, I Installed a separate switch to a separate solenoid which fed battery to the glow plugs so I could over ride the automatic switch. Never had to glow much more than 10 seconds, but it allowed me to try again, if needed, without waiting.

Paul T
 
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