ZD21 smoke on start-up

GMCRanch

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B2301 TL &attachments, ZD21F
Jun 16, 2021
12
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1
MD
make sure to ask the dealer to do a compression test before doing anything else. That'll give you an idea of the condition of the engine's internals.

Then ask them to do a valve adjustment just for kicks and giggles. Ask them for a worksheet. In other words, have them log the clearance before and after adjustment. I'd be surprised if they are much more than .02-.05mm off either way of spec. Then have 'em do a compression test again after adjusting the valves. These little diesels (well anything smaller than about 2.0L of displacement) are really sensitive to compression gas leaks, in other words it don't take much to bleed off enough air to make them run like poo. The usual complaint is that they're hard to start and/or smoky/rough starts. It just gets worse over time to the point where that cylinder will just not run at all. Diesels need to compress air to a pressure high enough that there is sufficient heat for the fuel to ignite almost instantaneously, on most of the Kubota's, typically 400 psi or greater. They'll run at lower pressures but again they get smoky and loss of power becomes an issue.
I've noticed a slight ticking sound as well which to me sounded like lifter tap but I wasn't sure if it was that or fuel related since it seems like it gets more than it needs. I'd hope they don't find that it's on its way out the door. But I definitely will, I'm sure they'll think I'm "that" customer but it's my machine I'm paying them to go over it and I want it right lol.
 

lugbolt

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ZG127S-54
Oct 15, 2015
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you will never hear the lifters ticking on these engines, most diesels for that matter. So if you hear a ticking, you may have more trouble than you think. But for sure, ask them to check the valves-and compression pressures. They're really easy to get to everything to do both of those, so I figure (in my best guess) about an hour & a half labor to do a compression and valve check on a ZD21.

a little puff of black smoke on startup is perfectly normal, BTW. Should be gone in less than a second.
 

GMCRanch

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B2301 TL &attachments, ZD21F
Jun 16, 2021
12
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MD
That's what worries me, and yes the black smoke is what I want to see like my B2301 when it starts. A small puff and that's it not the white smoke that comes out of the mower. I hope it's not on it's way out the door but that's ultimately the risk I took buying a used machine
 

jimh406

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Kubota L2501 with R4 tires
Jan 29, 2021
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My experience is tha Rotella synthetic eliminates a lot of noise. Also, Seafoam helps make engines run better. Finally, PowerService Diesel Kleen helps as well. They are all relatively cheap things to try.

Good luck!
 

ManBitesDog

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Currently Shopping
Jul 8, 2021
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The 'ticking' is very likely injector noise. And I'm not a fan of distilled water in my cooling system. Research it and you'll find that I'm not the only one. It's better than tap water, but not by a whole lot.

Also, check your oil level between changes just to see if the level is rising. Sometimes, diesel injectors can leak and dilute the engine oil. I thought of that only because of the smoke on cold starts.
 

GMCRanch

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B2301 TL &attachments, ZD21F
Jun 16, 2021
12
0
1
MD
All very good points, fixing those broken soft fuel hoses really did make it start a lot easier (obviously now there's no fuel leak/no air in the lines) and I will check to see if I can smell fuel in the oil. Similar to the 6.4 powerstroke issues with fuel in the oil and the damage that can cause. I flushed the block with the hose for water pressure then filled with the Prestone premix. I know hose water is inevitably still in the block but hopefully a minimal amount. Anything is better than the rusty mess that came out of it. I was hesitant on sea foaming a diesel but I'll try it. I just did an oil and filter change but I always buy in bulk so I could sea foam it and get the engine really clean and see if that helps some and change it again. I put the Kubota 10-30 in it but if synthetic quiets it down I'll happily switch. It's not obnoxious but compared to my B2301 it's noticeable that the ZD21 definitely has a tick. I've tightened the rocker cover bolts since I've gotten it because the center one was leaking a little oil and I've noticed it is still leaking but not as bad. Makes me wonder about that too. Probably just not tight enough. Like I said it's a used machine that is in physically good shape but it makes me wonder what all it has been through previously given the nasty coolant for example. It seems a lot happier now that it's been gone through and still no leaks.
 

GMCRanch

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B2301 TL &attachments, ZD21F
Jun 16, 2021
12
0
1
MD
Something very interesting happened today. It's been about a week and a half since I've last run the mower. I have burned about half a tank of fuel with BG injector cleaner in it like suggested on here. Haven't done the sea foam yet. Anyhow I turned the key after the glow light went out and it started right up the second I turned the key with very little smoke, sputtering etc. I let it idle a minute while unloading my truck from vacation and turned it back off. I re started it because I couldn't belive it and sure enough (obviously warmed up some) barely even any black smoke. It still has that tapping/ticking noise though which I'm concerned over. I know these small diesels aren't exactly quiet but so far no noticeable oil level increase or smell of fuel in the oil either. No leaks other than a slight drip from the drain plug which was a tad loose. I don't crank down on them but I didn't snug this one enough apparently. Or it needs a new crush washer. I wonder if it's a fluke or if the injector cleaner is doing the trick?