Kubota won't start & puffs blue smoke

[rhamer]

I have a Kubota L1802DT (D1102 engine) that has just started giving me a bit of trouble.

On 2 occasions recently when starting it has gone to full revs for about 5 secounds before returning to idle. The first time it did it, I thought I must have had my foot on the throttle, but the second time, definately not.

On 2 other occasions it has refused to start and just turned over endlessly whilst puffing blue smoke out the exhaust. Eventually it has started, and is fine after that, no smoke at all. I have noticed however that it feels down on power a bit as I have to have the throttle wider open to achieve the same revs as before. Also it now stalls if I close the throttle completely.

The tractor is a grey import that had the engine completely rebuilt when imported. It only has 100 hours on it, but that is over 5 years so I'm wondering if it just needs a proper service?

Any advice would be gratefully accepted.

Cheers

Rohan

 

[tawilson]

I'd pop a new fuel filter in it first.

 

[banjodunn]

G'day as said pop in a fuel filter and check the air filter also are the glow plugs working ?


Jon

 

[jinman]

I have a mower with a small Kubota diesel that "puffs" when I don't cycle the glow plugs long enough. My guess is that your glowplugs are also failing or not operating properly.

 

[Tig]

To me blue smoke means oil. If only on start, then I would wonder if it was leaking down worn valve stems like the old V8s did when they were shut off.
If I don't preheat my B7100 enough, I get white smoke on start.
Compression test might be a good idea to give you some peace of mind for both the smoke and low power issues.
Just my 2cents.

 

[Soundguy]

I'd do all the free/cheap stuff mentioned here first.. IE.. new fuel filter/air filter, and a test of any pre-heat systems. if those all check out and still hard starts, I'd also run a good tank full of treated fuel with something to clean the injectors.

the full throttle for a couple seconds may have been a sticky rack...

I reccomend the brestone 'blue bottle' diesel fuel system cleaner.. made a notible difference in 2 of my machines that i was thinking had some dirty fuel issues..

soundguy

 

[rhamer]

Thanks for the hints guys, I'm hoping it's something easy.

Is it just a matter of removing the glow plugs and checking them with an ohmmeter? I should check there is voltage to them as well?

I also see pepole say to do thingslike 'crack' the injectors and check there is fuel. I've never worked on a diesel (but done whole engine builds on petrol motors) so I don't know what exactly to expect.

BTW what is a sticky rack?

Thanks again and keep the advice coming.

Regards

Rohan

 

[irvingj]

"Sticky rack" I believe refers to the stroke-length mechanism in the injector pump (hooked to the throttle pedal, determines how much fuel is delivered to each injector)-- best to leave that to specialists, other than an injector cleaner additive.

You can at least check for continuity on the glow plugs by disconnecting the electrical lead, then check with an ohmmeter from the plug top (where wire hooks on) to ground. If you get a reading, at least you know it's not burnt out. If you get an "open" reading, the glow plug's most likely toast. Anything further, you'll have to pull the glow plugs to bench test. And yes, making sure the glow plug harness is getting voltage would be step #1 or step #2.

I used to have to do this procedure pretty often on my old Peugeot 504D wagon....

 

[rhamer]

I havn't solved the problem yet, but I pulled out the fuel filter and glow plugs today.

The fuel filter looks clean, but I'll replace it anyway.

I did find that I had 2 different types of glow plugs.

2 x NGK Y-106 V
1 x NGK Y-702 U

I think I know why the plugs were odd as the 702 was in cyl 1 and was a dog to get out. I had to grind down a socket to get it past the intake manifold.

The 702 has a much higher resistance than the other 2, which leads me to believe its broken. I believe the resistance of a good plug is around 1 ohm.

So if 1 plug out of 3 was not heating, would that stop the engine from starting?

Cheers

Rohan

 

[irvingj]

Sounds like somebody was just too busy to get that #1 out.... It's a shame to see "shortcuts" like that.

If you get any resistance at all, the glow plug will generate some heat, but yeah, higher resistance could mean a poor internal connection (barring a difference in the basic resistance of the two types of plug).

If one glow plug out of the three wasn't working, yes, that would add some difficulty to the starting, but it ought to still start-- just smoke like a son of a gun and "misfire" on the cylinder in question, along with a lot of smoke and rough running --stumbling, perhaps stalling-- as a result of same. And yes, if diesel fuel isn't igniting/burning properly, that will lead to blue smoke, about the same as if it were running very rich (due to a clogged air filter or similar).

One way to see if it's the glow plugs causing the problem would be to simulate warm weather coditions: heat the intake manifold --hair dryer/heat gun...?-- and see if it starts without issue. If it does start OK, then yes, most likely glow plugs aren't doing their job.